]>
Commit | Line | Data |
---|---|---|
1b1d2e6d BP |
1 | /* |
2 | * Copyright (c) 2017, 2018 Nicira, Inc. | |
3 | * | |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); | |
5 | * you may not use this file except in compliance with the License. | |
6 | * You may obtain a copy of the License at: | |
7 | * | |
8 | * http://www.apache.org/licenses/LICENSE-2.0 | |
9 | * | |
10 | * Unless required by applicable law or agreed to in writing, software | |
11 | * distributed under the License is distributed on an "AS IS" BASIS, | |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
13 | * See the License for the specific language governing permissions and | |
14 | * limitations under the License. | |
15 | */ | |
16 | ||
17 | #include <config.h> | |
18 | ||
19 | #include "raft.h" | |
20 | #include "raft-private.h" | |
21 | ||
22 | #include <errno.h> | |
23 | #include <unistd.h> | |
24 | ||
25 | #include "hash.h" | |
26 | #include "jsonrpc.h" | |
27 | #include "lockfile.h" | |
28 | #include "openvswitch/dynamic-string.h" | |
29 | #include "openvswitch/hmap.h" | |
30 | #include "openvswitch/json.h" | |
31 | #include "openvswitch/list.h" | |
32 | #include "openvswitch/poll-loop.h" | |
33 | #include "openvswitch/vlog.h" | |
34 | #include "ovsdb-error.h" | |
35 | #include "ovsdb-parser.h" | |
36 | #include "ovsdb/log.h" | |
37 | #include "raft-rpc.h" | |
38 | #include "random.h" | |
39 | #include "socket-util.h" | |
40 | #include "stream.h" | |
41 | #include "timeval.h" | |
42 | #include "unicode.h" | |
43 | #include "unixctl.h" | |
44 | #include "util.h" | |
45 | #include "uuid.h" | |
46 | ||
47 | VLOG_DEFINE_THIS_MODULE(raft); | |
48 | ||
49 | /* Roles for a Raft server: | |
50 | * | |
51 | * - Followers: Servers in touch with the current leader. | |
52 | * | |
53 | * - Candidate: Servers unaware of a current leader and seeking election to | |
54 | * leader. | |
55 | * | |
56 | * - Leader: Handles all client requests. At most one at a time. | |
57 | * | |
58 | * In normal operation there is exactly one leader and all of the other servers | |
59 | * are followers. */ | |
60 | enum raft_role { | |
61 | RAFT_FOLLOWER, | |
62 | RAFT_CANDIDATE, | |
63 | RAFT_LEADER | |
64 | }; | |
65 | ||
66 | /* A connection between this Raft server and another one. */ | |
67 | struct raft_conn { | |
68 | struct ovs_list list_node; /* In struct raft's 'conns' list. */ | |
69 | struct jsonrpc_session *js; /* JSON-RPC connection. */ | |
70 | struct uuid sid; /* This server's unique ID. */ | |
71 | char *nickname; /* Short name for use in log messages. */ | |
72 | bool incoming; /* True if incoming, false if outgoing. */ | |
73 | unsigned int js_seqno; /* Seqno for noticing (re)connections. */ | |
74 | }; | |
75 | ||
76 | static void raft_conn_close(struct raft_conn *); | |
77 | ||
78 | /* A "command", that is, a request to append an entry to the log. | |
79 | * | |
80 | * The Raft specification only allows clients to issue commands to the leader. | |
81 | * With this implementation, clients may issue a command on any server, which | |
82 | * then relays the command to the leader if necessary. | |
83 | * | |
84 | * This structure is thus used in three cases: | |
85 | * | |
86 | * 1. We are the leader and the command was issued to us directly. | |
87 | * | |
88 | * 2. We are a follower and relayed the command to the leader. | |
89 | * | |
90 | * 3. We are the leader and a follower relayed the command to us. | |
91 | */ | |
92 | struct raft_command { | |
93 | /* All cases. */ | |
94 | struct hmap_node hmap_node; /* In struct raft's 'commands' hmap. */ | |
95 | unsigned int n_refs; /* Reference count. */ | |
96 | enum raft_command_status status; /* Execution status. */ | |
97 | ||
98 | /* Case 1 only. */ | |
99 | uint64_t index; /* Index in log (0 if being relayed). */ | |
100 | ||
101 | /* Cases 2 and 3. */ | |
102 | struct uuid eid; /* Entry ID of result. */ | |
103 | ||
104 | /* Case 2 only. */ | |
105 | long long int timestamp; /* Issue or last ping time, for expiration. */ | |
106 | ||
107 | /* Case 3 only. */ | |
108 | struct uuid sid; /* The follower (otherwise UUID_ZERO). */ | |
109 | }; | |
110 | ||
111 | static void raft_command_complete(struct raft *, struct raft_command *, | |
112 | enum raft_command_status); | |
113 | ||
114 | static void raft_complete_all_commands(struct raft *, | |
115 | enum raft_command_status); | |
116 | ||
117 | /* Type of deferred action, see struct raft_waiter. */ | |
118 | enum raft_waiter_type { | |
119 | RAFT_W_ENTRY, | |
120 | RAFT_W_TERM, | |
121 | RAFT_W_RPC, | |
122 | }; | |
123 | ||
124 | /* An action deferred until a log write commits to disk. */ | |
125 | struct raft_waiter { | |
126 | struct ovs_list list_node; | |
127 | uint64_t commit_ticket; | |
128 | ||
129 | enum raft_waiter_type type; | |
130 | union { | |
131 | /* RAFT_W_ENTRY. | |
132 | * | |
133 | * Waits for a RAFT_REC_ENTRY write to our local log to commit. Upon | |
134 | * completion, updates 'log_synced' to indicate that the new log entry | |
135 | * or entries are committed and, if we are leader, also updates our | |
136 | * local 'match_index'. */ | |
137 | struct { | |
138 | uint64_t index; | |
139 | } entry; | |
140 | ||
141 | /* RAFT_W_TERM. | |
142 | * | |
143 | * Waits for a RAFT_REC_TERM or RAFT_REC_VOTE record write to commit. | |
144 | * Upon completion, updates 'synced_term' and 'synced_vote', which | |
145 | * triggers sending RPCs deferred by the uncommitted 'term' and | |
146 | * 'vote'. */ | |
147 | struct { | |
148 | uint64_t term; | |
149 | struct uuid vote; | |
150 | } term; | |
151 | ||
152 | /* RAFT_W_RPC. | |
153 | * | |
154 | * Sometimes, sending an RPC to a peer must be delayed until an entry, | |
155 | * a term, or a vote mentioned in the RPC is synced to disk. This | |
156 | * waiter keeps a copy of such an RPC until the previous waiters have | |
157 | * committed. */ | |
158 | union raft_rpc *rpc; | |
159 | }; | |
160 | }; | |
161 | ||
162 | static struct raft_waiter *raft_waiter_create(struct raft *, | |
163 | enum raft_waiter_type, | |
164 | bool start_commit); | |
165 | static void raft_waiters_destroy(struct raft *); | |
166 | ||
167 | /* The Raft state machine. */ | |
168 | struct raft { | |
169 | struct hmap_node hmap_node; /* In 'all_rafts'. */ | |
170 | struct ovsdb_log *log; | |
171 | ||
172 | /* Persistent derived state. | |
173 | * | |
174 | * This must be updated on stable storage before responding to RPCs. It can be | |
175 | * derived from the header, snapshot, and log in 'log'. */ | |
176 | ||
177 | struct uuid cid; /* Cluster ID (immutable for the cluster). */ | |
178 | struct uuid sid; /* Server ID (immutable for the server). */ | |
179 | char *local_address; /* Local address (immutable for the server). */ | |
180 | char *local_nickname; /* Used for local server in log messages. */ | |
181 | char *name; /* Schema name (immutable for the cluster). */ | |
182 | ||
183 | /* Contains "struct raft_server"s and represents the server configuration | |
184 | * most recently added to 'log'. */ | |
185 | struct hmap servers; | |
186 | ||
187 | /* Persistent state on all servers. | |
188 | * | |
189 | * Must be updated on stable storage before responding to RPCs. */ | |
190 | ||
191 | /* Current term and the vote for that term. These might be on the way to | |
192 | * disk now. */ | |
193 | uint64_t term; /* Initialized to 0 and only increases. */ | |
194 | struct uuid vote; /* All-zeros if no vote yet in 'term'. */ | |
195 | ||
196 | /* The term and vote that have been synced to disk. */ | |
197 | uint64_t synced_term; | |
198 | struct uuid synced_vote; | |
199 | ||
200 | /* The log. | |
201 | * | |
202 | * A log entry with index 1 never really exists; the initial snapshot for a | |
203 | * Raft is considered to include this index. The first real log entry has | |
204 | * index 2. | |
205 | * | |
206 | * A new Raft instance contains an empty log: log_start=2, log_end=2. | |
207 | * Over time, the log grows: log_start=2, log_end=N. | |
208 | * At some point, the server takes a snapshot: log_start=N, log_end=N. | |
209 | * The log continues to grow: log_start=N, log_end=N+1... | |
210 | * | |
211 | * Must be updated on stable storage before responding to RPCs. */ | |
212 | struct raft_entry *entries; /* Log entry i is in log[i - log_start]. */ | |
213 | uint64_t log_start; /* Index of first entry in log. */ | |
214 | uint64_t log_end; /* Index of last entry in log, plus 1. */ | |
215 | uint64_t log_synced; /* Index of last synced entry. */ | |
216 | size_t allocated_log; /* Allocated entries in 'log'. */ | |
217 | ||
218 | /* Snapshot state (see Figure 5.1) | |
219 | * | |
220 | * This is the state of the cluster as of the last discarded log entry, | |
221 | * that is, at log index 'log_start - 1' (called prevIndex in Figure 5.1). | |
222 | * Only committed log entries can be included in a snapshot. */ | |
223 | struct raft_entry snap; | |
224 | ||
225 | /* Volatile state. | |
226 | * | |
227 | * The snapshot is always committed, but the rest of the log might not be yet. | |
228 | * 'last_applied' tracks what entries have been passed to the client. If the | |
229 | * client hasn't yet read the latest snapshot, then even the snapshot isn't | |
230 | * applied yet. Thus, the invariants are different for these members: | |
231 | * | |
232 | * log_start - 2 <= last_applied <= commit_index < log_end. | |
233 | * log_start - 1 <= commit_index < log_end. | |
234 | */ | |
235 | ||
236 | enum raft_role role; /* Current role. */ | |
237 | uint64_t commit_index; /* Max log index known to be committed. */ | |
238 | uint64_t last_applied; /* Max log index applied to state machine. */ | |
239 | struct uuid leader_sid; /* Server ID of leader (zero, if unknown). */ | |
240 | ||
241 | /* Followers and candidates only. */ | |
242 | #define ELECTION_BASE_MSEC 1024 | |
243 | #define ELECTION_RANGE_MSEC 1024 | |
244 | long long int election_base; /* Time of last heartbeat from leader. */ | |
245 | long long int election_timeout; /* Time at which we start an election. */ | |
246 | ||
247 | /* Used for joining a cluster. */ | |
248 | bool joining; /* Attempting to join the cluster? */ | |
249 | struct sset remote_addresses; /* Addresses to try to find other servers. */ | |
250 | long long int join_timeout; /* Time to re-send add server request. */ | |
251 | ||
252 | /* Used for leaving a cluster. */ | |
253 | bool leaving; /* True if we are leaving the cluster. */ | |
254 | bool left; /* True if we have finished leaving. */ | |
255 | long long int leave_timeout; /* Time to re-send remove server request. */ | |
256 | ||
257 | /* Failure. */ | |
258 | bool failed; /* True if unrecoverable error has occurred. */ | |
259 | ||
260 | /* File synchronization. */ | |
261 | struct ovs_list waiters; /* Contains "struct raft_waiter"s. */ | |
262 | ||
263 | /* Network connections. */ | |
264 | struct pstream *listener; /* For connections from other Raft servers. */ | |
265 | long long int listen_backoff; /* For retrying creating 'listener'. */ | |
266 | struct ovs_list conns; /* Contains struct raft_conns. */ | |
267 | ||
268 | /* Leaders only. Reinitialized after becoming leader. */ | |
269 | struct hmap add_servers; /* Contains "struct raft_server"s to add. */ | |
270 | struct raft_server *remove_server; /* Server being removed. */ | |
271 | struct hmap commands; /* Contains "struct raft_command"s. */ | |
272 | #define PING_TIME_MSEC (ELECTION_BASE_MSEC / 3) | |
273 | long long int ping_timeout; /* Time at which to send a heartbeat */ | |
274 | ||
275 | /* Candidates only. Reinitialized at start of election. */ | |
276 | int n_votes; /* Number of votes for me. */ | |
277 | }; | |
278 | ||
279 | /* All Raft structures. */ | |
280 | static struct hmap all_rafts = HMAP_INITIALIZER(&all_rafts); | |
281 | ||
282 | static void raft_init(void); | |
283 | ||
284 | static struct ovsdb_error *raft_read_header(struct raft *) | |
285 | OVS_WARN_UNUSED_RESULT; | |
286 | ||
287 | static void raft_send_execute_command_reply(struct raft *, | |
288 | const struct uuid *sid, | |
289 | const struct uuid *eid, | |
290 | enum raft_command_status, | |
291 | uint64_t commit_index); | |
292 | ||
293 | static void raft_update_our_match_index(struct raft *, uint64_t min_index); | |
294 | ||
295 | static void raft_send_remove_server_reply__( | |
296 | struct raft *, const struct uuid *target_sid, | |
297 | const struct uuid *requester_sid, struct unixctl_conn *requester_conn, | |
298 | bool success, const char *comment); | |
299 | ||
300 | static void raft_server_init_leader(struct raft *, struct raft_server *); | |
301 | ||
302 | static bool raft_rpc_is_heartbeat(const union raft_rpc *); | |
303 | static bool raft_is_rpc_synced(const struct raft *, const union raft_rpc *); | |
304 | ||
305 | static void raft_handle_rpc(struct raft *, const union raft_rpc *); | |
306 | static bool raft_send(struct raft *, const union raft_rpc *); | |
307 | static bool raft_send__(struct raft *, const union raft_rpc *, | |
308 | struct raft_conn *); | |
309 | static void raft_send_append_request(struct raft *, | |
310 | struct raft_server *, unsigned int n, | |
311 | const char *comment); | |
312 | ||
313 | static void raft_become_leader(struct raft *); | |
314 | static void raft_become_follower(struct raft *); | |
315 | static void raft_reset_timer(struct raft *); | |
316 | static void raft_send_heartbeats(struct raft *); | |
317 | static void raft_start_election(struct raft *, bool leadership_transfer); | |
318 | static bool raft_truncate(struct raft *, uint64_t new_end); | |
319 | static void raft_get_servers_from_log(struct raft *, enum vlog_level); | |
320 | ||
321 | static bool raft_handle_write_error(struct raft *, struct ovsdb_error *); | |
322 | ||
323 | static void raft_run_reconfigure(struct raft *); | |
324 | ||
325 | static struct raft_server * | |
326 | raft_find_server(const struct raft *raft, const struct uuid *sid) | |
327 | { | |
328 | return raft_server_find(&raft->servers, sid); | |
329 | } | |
330 | ||
331 | static char * | |
332 | raft_make_address_passive(const char *address_) | |
333 | { | |
334 | if (!strncmp(address_, "unix:", 5)) { | |
335 | return xasprintf("p%s", address_); | |
336 | } else { | |
337 | char *address = xstrdup(address_); | |
0b043300 BP |
338 | char *host, *port; |
339 | inet_parse_host_port_tokens(strchr(address, ':') + 1, &host, &port); | |
1b1d2e6d BP |
340 | |
341 | struct ds paddr = DS_EMPTY_INITIALIZER; | |
342 | ds_put_format(&paddr, "p%.3s:%s:", address, port); | |
343 | if (strchr(host, ':')) { | |
344 | ds_put_format(&paddr, "[%s]", host); | |
345 | } else { | |
346 | ds_put_cstr(&paddr, host); | |
347 | } | |
348 | free(address); | |
349 | return ds_steal_cstr(&paddr); | |
350 | } | |
351 | } | |
352 | ||
353 | static struct raft * | |
354 | raft_alloc(void) | |
355 | { | |
356 | raft_init(); | |
357 | ||
358 | struct raft *raft = xzalloc(sizeof *raft); | |
359 | hmap_node_nullify(&raft->hmap_node); | |
360 | hmap_init(&raft->servers); | |
361 | raft->log_start = raft->log_end = 1; | |
362 | raft->role = RAFT_FOLLOWER; | |
363 | sset_init(&raft->remote_addresses); | |
364 | raft->join_timeout = LLONG_MAX; | |
365 | ovs_list_init(&raft->waiters); | |
366 | raft->listen_backoff = LLONG_MIN; | |
367 | ovs_list_init(&raft->conns); | |
368 | hmap_init(&raft->add_servers); | |
369 | hmap_init(&raft->commands); | |
370 | ||
371 | raft->ping_timeout = time_msec() + PING_TIME_MSEC; | |
372 | raft_reset_timer(raft); | |
373 | ||
374 | return raft; | |
375 | } | |
376 | ||
377 | /* Creates an on-disk file that represents a new Raft cluster and initializes | |
378 | * it to consist of a single server, the one on which this function is called. | |
379 | * | |
380 | * Creates the local copy of the cluster's log in 'file_name', which must not | |
381 | * already exist. Gives it the name 'name', which should be the database | |
382 | * schema name and which is used only to match up this database with the server | |
383 | * added to the cluster later if the cluster ID is unavailable. | |
384 | * | |
385 | * The new server is located at 'local_address', which must take one of the | |
386 | * forms "tcp:IP:PORT" or "ssl:IP:PORT", where IP is an IPv4 address or a | |
387 | * square bracket enclosed IPv6 address and PORT is a TCP port number. | |
388 | * | |
389 | * This only creates the on-disk file. Use raft_open() to start operating the | |
390 | * new server. | |
391 | * | |
392 | * Returns null if successful, otherwise an ovsdb_error describing the | |
393 | * problem. */ | |
394 | struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
395 | raft_create_cluster(const char *file_name, const char *name, | |
396 | const char *local_address, const struct json *data) | |
397 | { | |
398 | /* Parse and verify validity of the local address. */ | |
399 | struct ovsdb_error *error = raft_address_validate(local_address); | |
400 | if (error) { | |
401 | return error; | |
402 | } | |
403 | ||
404 | /* Create log file. */ | |
405 | struct ovsdb_log *log; | |
406 | error = ovsdb_log_open(file_name, RAFT_MAGIC, OVSDB_LOG_CREATE_EXCL, | |
407 | -1, &log); | |
408 | if (error) { | |
409 | return error; | |
410 | } | |
411 | ||
412 | /* Write log file. */ | |
413 | struct raft_header h = { | |
414 | .sid = uuid_random(), | |
415 | .cid = uuid_random(), | |
416 | .name = xstrdup(name), | |
417 | .local_address = xstrdup(local_address), | |
418 | .joining = false, | |
419 | .remote_addresses = SSET_INITIALIZER(&h.remote_addresses), | |
420 | .snap_index = 1, | |
421 | .snap = { | |
422 | .term = 1, | |
423 | .data = json_nullable_clone(data), | |
424 | .eid = uuid_random(), | |
425 | .servers = json_object_create(), | |
426 | }, | |
427 | }; | |
428 | shash_add_nocopy(json_object(h.snap.servers), | |
429 | xasprintf(UUID_FMT, UUID_ARGS(&h.sid)), | |
430 | json_string_create(local_address)); | |
431 | error = ovsdb_log_write_and_free(log, raft_header_to_json(&h)); | |
432 | raft_header_uninit(&h); | |
433 | if (!error) { | |
434 | error = ovsdb_log_commit_block(log); | |
435 | } | |
436 | ovsdb_log_close(log); | |
437 | ||
438 | return error; | |
439 | } | |
440 | ||
441 | /* Creates a database file that represents a new server in an existing Raft | |
442 | * cluster. | |
443 | * | |
444 | * Creates the local copy of the cluster's log in 'file_name', which must not | |
445 | * already exist. Gives it the name 'name', which must be the same name | |
446 | * passed in to raft_create_cluster() earlier. | |
447 | * | |
448 | * 'cid' is optional. If specified, the new server will join only the cluster | |
449 | * with the given cluster ID. | |
450 | * | |
451 | * The new server is located at 'local_address', which must take one of the | |
452 | * forms "tcp:IP:PORT" or "ssl:IP:PORT", where IP is an IPv4 address or a | |
453 | * square bracket enclosed IPv6 address and PORT is a TCP port number. | |
454 | * | |
455 | * Joining the cluster requires contacting it. Thus, 'remote_addresses' | |
456 | * specifies the addresses of existing servers in the cluster. One server out | |
457 | * of the existing cluster is sufficient, as long as that server is reachable | |
458 | * and not partitioned from the current cluster leader. If multiple servers | |
459 | * from the cluster are specified, then it is sufficient for any of them to | |
460 | * meet this criterion. | |
461 | * | |
462 | * This only creates the on-disk file and does no network access. Use | |
463 | * raft_open() to start operating the new server. (Until this happens, the | |
464 | * new server has not joined the cluster.) | |
465 | * | |
466 | * Returns null if successful, otherwise an ovsdb_error describing the | |
467 | * problem. */ | |
468 | struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
469 | raft_join_cluster(const char *file_name, | |
470 | const char *name, const char *local_address, | |
471 | const struct sset *remote_addresses, | |
472 | const struct uuid *cid) | |
473 | { | |
474 | ovs_assert(!sset_is_empty(remote_addresses)); | |
475 | ||
476 | /* Parse and verify validity of the addresses. */ | |
477 | struct ovsdb_error *error = raft_address_validate(local_address); | |
478 | if (error) { | |
479 | return error; | |
480 | } | |
481 | const char *addr; | |
482 | SSET_FOR_EACH (addr, remote_addresses) { | |
483 | error = raft_address_validate(addr); | |
484 | if (error) { | |
485 | return error; | |
486 | } | |
487 | if (!strcmp(addr, local_address)) { | |
488 | return ovsdb_error(NULL, "remote addresses cannot be the same " | |
489 | "as the local address"); | |
490 | } | |
491 | } | |
492 | ||
493 | /* Verify validity of the cluster ID (if provided). */ | |
494 | if (cid && uuid_is_zero(cid)) { | |
495 | return ovsdb_error(NULL, "all-zero UUID is not valid cluster ID"); | |
496 | } | |
497 | ||
498 | /* Create log file. */ | |
499 | struct ovsdb_log *log; | |
500 | error = ovsdb_log_open(file_name, RAFT_MAGIC, OVSDB_LOG_CREATE_EXCL, | |
501 | -1, &log); | |
502 | if (error) { | |
503 | return error; | |
504 | } | |
505 | ||
506 | /* Write log file. */ | |
507 | struct raft_header h = { | |
508 | .sid = uuid_random(), | |
509 | .cid = cid ? *cid : UUID_ZERO, | |
510 | .name = xstrdup(name), | |
511 | .local_address = xstrdup(local_address), | |
512 | .joining = true, | |
513 | /* No snapshot yet. */ | |
514 | }; | |
515 | sset_clone(&h.remote_addresses, remote_addresses); | |
516 | error = ovsdb_log_write_and_free(log, raft_header_to_json(&h)); | |
517 | raft_header_uninit(&h); | |
518 | if (!error) { | |
519 | error = ovsdb_log_commit_block(log); | |
520 | } | |
521 | ovsdb_log_close(log); | |
522 | ||
523 | return error; | |
524 | } | |
525 | ||
526 | /* Reads the initial header record from 'log', which must be a Raft clustered | |
527 | * database log, and populates '*md' with the information read from it. The | |
528 | * caller must eventually destroy 'md' with raft_metadata_destroy(). | |
529 | * | |
530 | * On success, returns NULL. On failure, returns an error that the caller must | |
531 | * eventually destroy and zeros '*md'. */ | |
532 | struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
533 | raft_read_metadata(struct ovsdb_log *log, struct raft_metadata *md) | |
534 | { | |
535 | struct raft *raft = raft_alloc(); | |
536 | raft->log = log; | |
537 | ||
538 | struct ovsdb_error *error = raft_read_header(raft); | |
539 | if (!error) { | |
540 | md->sid = raft->sid; | |
541 | md->name = xstrdup(raft->name); | |
542 | md->local = xstrdup(raft->local_address); | |
543 | md->cid = raft->cid; | |
544 | } else { | |
545 | memset(md, 0, sizeof *md); | |
546 | } | |
547 | ||
548 | raft->log = NULL; | |
549 | raft_close(raft); | |
550 | return error; | |
551 | } | |
552 | ||
553 | /* Frees the metadata in 'md'. */ | |
554 | void | |
555 | raft_metadata_destroy(struct raft_metadata *md) | |
556 | { | |
557 | if (md) { | |
558 | free(md->name); | |
559 | free(md->local); | |
560 | } | |
561 | } | |
562 | ||
563 | static const struct raft_entry * | |
564 | raft_get_entry(const struct raft *raft, uint64_t index) | |
565 | { | |
566 | ovs_assert(index >= raft->log_start); | |
567 | ovs_assert(index < raft->log_end); | |
568 | return &raft->entries[index - raft->log_start]; | |
569 | } | |
570 | ||
571 | static uint64_t | |
572 | raft_get_term(const struct raft *raft, uint64_t index) | |
573 | { | |
574 | return (index == raft->log_start - 1 | |
575 | ? raft->snap.term | |
576 | : raft_get_entry(raft, index)->term); | |
577 | } | |
578 | ||
579 | static const struct json * | |
580 | raft_servers_for_index(const struct raft *raft, uint64_t index) | |
581 | { | |
582 | ovs_assert(index >= raft->log_start - 1); | |
583 | ovs_assert(index < raft->log_end); | |
584 | ||
585 | const struct json *servers = raft->snap.servers; | |
586 | for (uint64_t i = raft->log_start; i <= index; i++) { | |
587 | const struct raft_entry *e = raft_get_entry(raft, i); | |
588 | if (e->servers) { | |
589 | servers = e->servers; | |
590 | } | |
591 | } | |
592 | return servers; | |
593 | } | |
594 | ||
595 | static void | |
596 | raft_set_servers(struct raft *raft, const struct hmap *new_servers, | |
597 | enum vlog_level level) | |
598 | { | |
599 | struct raft_server *s, *next; | |
600 | HMAP_FOR_EACH_SAFE (s, next, hmap_node, &raft->servers) { | |
601 | if (!raft_server_find(new_servers, &s->sid)) { | |
602 | ovs_assert(s != raft->remove_server); | |
603 | ||
604 | hmap_remove(&raft->servers, &s->hmap_node); | |
605 | VLOG(level, "server %s removed from configuration", s->nickname); | |
606 | raft_server_destroy(s); | |
607 | } | |
608 | } | |
609 | ||
610 | HMAP_FOR_EACH_SAFE (s, next, hmap_node, new_servers) { | |
611 | if (!raft_find_server(raft, &s->sid)) { | |
612 | VLOG(level, "server %s added to configuration", s->nickname); | |
613 | ||
614 | struct raft_server *new | |
615 | = raft_server_add(&raft->servers, &s->sid, s->address); | |
616 | raft_server_init_leader(raft, new); | |
617 | } | |
618 | } | |
619 | } | |
620 | ||
621 | static uint64_t | |
622 | raft_add_entry(struct raft *raft, | |
623 | uint64_t term, struct json *data, const struct uuid *eid, | |
624 | struct json *servers) | |
625 | { | |
626 | if (raft->log_end - raft->log_start >= raft->allocated_log) { | |
627 | raft->entries = x2nrealloc(raft->entries, &raft->allocated_log, | |
628 | sizeof *raft->entries); | |
629 | } | |
630 | ||
631 | uint64_t index = raft->log_end++; | |
632 | struct raft_entry *entry = &raft->entries[index - raft->log_start]; | |
633 | entry->term = term; | |
634 | entry->data = data; | |
635 | entry->eid = eid ? *eid : UUID_ZERO; | |
636 | entry->servers = servers; | |
637 | return index; | |
638 | } | |
639 | ||
640 | /* Writes a RAFT_REC_ENTRY record for 'term', 'data', 'eid', 'servers' to | |
641 | * 'raft''s log and returns an error indication. */ | |
642 | static struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
643 | raft_write_entry(struct raft *raft, uint64_t term, struct json *data, | |
644 | const struct uuid *eid, struct json *servers) | |
645 | { | |
646 | struct raft_record r = { | |
647 | .type = RAFT_REC_ENTRY, | |
648 | .term = term, | |
649 | .entry = { | |
650 | .index = raft_add_entry(raft, term, data, eid, servers), | |
651 | .data = data, | |
652 | .servers = servers, | |
653 | .eid = eid ? *eid : UUID_ZERO, | |
654 | }, | |
655 | }; | |
656 | return ovsdb_log_write_and_free(raft->log, raft_record_to_json(&r)); | |
657 | } | |
658 | ||
659 | static struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
660 | raft_write_state(struct ovsdb_log *log, | |
661 | uint64_t term, const struct uuid *vote) | |
662 | { | |
663 | struct raft_record r = { .term = term }; | |
664 | if (vote && !uuid_is_zero(vote)) { | |
665 | r.type = RAFT_REC_VOTE; | |
666 | r.sid = *vote; | |
667 | } else { | |
668 | r.type = RAFT_REC_TERM; | |
669 | } | |
670 | return ovsdb_log_write_and_free(log, raft_record_to_json(&r)); | |
671 | } | |
672 | ||
673 | static struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
674 | raft_apply_record(struct raft *raft, unsigned long long int rec_idx, | |
675 | const struct raft_record *r) | |
676 | { | |
677 | /* Apply "term", which is present in most kinds of records (and otherwise | |
678 | * 0). | |
679 | * | |
680 | * A Raft leader can replicate entries from previous terms to the other | |
681 | * servers in the cluster, retaining the original terms on those entries | |
682 | * (see section 3.6.2 "Committing entries from previous terms" for more | |
683 | * information), so it's OK for the term in a log record to precede the | |
684 | * current term. */ | |
685 | if (r->term > raft->term) { | |
686 | raft->term = raft->synced_term = r->term; | |
687 | raft->vote = raft->synced_vote = UUID_ZERO; | |
688 | } | |
689 | ||
690 | switch (r->type) { | |
691 | case RAFT_REC_ENTRY: | |
692 | if (r->entry.index < raft->commit_index) { | |
693 | return ovsdb_error(NULL, "record %llu attempts to truncate log " | |
694 | "from %"PRIu64" to %"PRIu64" entries, but " | |
695 | "commit index is already %"PRIu64, | |
696 | rec_idx, raft->log_end, r->entry.index, | |
697 | raft->commit_index); | |
698 | } else if (r->entry.index > raft->log_end) { | |
699 | return ovsdb_error(NULL, "record %llu with index %"PRIu64" skips " | |
700 | "past expected index %"PRIu64, | |
701 | rec_idx, r->entry.index, raft->log_end); | |
702 | } | |
703 | ||
704 | if (r->entry.index < raft->log_end) { | |
705 | /* This can happen, but it is notable. */ | |
706 | VLOG_DBG("record %llu truncates log from %"PRIu64" to %"PRIu64 | |
707 | " entries", rec_idx, raft->log_end, r->entry.index); | |
708 | raft_truncate(raft, r->entry.index); | |
709 | } | |
710 | ||
711 | uint64_t prev_term = (raft->log_end > raft->log_start | |
712 | ? raft->entries[raft->log_end | |
713 | - raft->log_start - 1].term | |
714 | : raft->snap.term); | |
715 | if (r->term < prev_term) { | |
716 | return ovsdb_error(NULL, "record %llu with index %"PRIu64" term " | |
717 | "%"PRIu64" precedes previous entry's term " | |
718 | "%"PRIu64, | |
719 | rec_idx, r->entry.index, r->term, prev_term); | |
720 | } | |
721 | ||
722 | raft->log_synced = raft_add_entry( | |
723 | raft, r->term, | |
724 | json_nullable_clone(r->entry.data), &r->entry.eid, | |
725 | json_nullable_clone(r->entry.servers)); | |
726 | return NULL; | |
727 | ||
728 | case RAFT_REC_TERM: | |
729 | return NULL; | |
730 | ||
731 | case RAFT_REC_VOTE: | |
732 | if (r->term < raft->term) { | |
733 | return ovsdb_error(NULL, "record %llu votes for term %"PRIu64" " | |
734 | "but current term is %"PRIu64, | |
735 | rec_idx, r->term, raft->term); | |
736 | } else if (!uuid_is_zero(&raft->vote) | |
737 | && !uuid_equals(&raft->vote, &r->sid)) { | |
738 | return ovsdb_error(NULL, "record %llu votes for "SID_FMT" in term " | |
739 | "%"PRIu64" but a previous record for the " | |
740 | "same term voted for "SID_FMT, rec_idx, | |
741 | SID_ARGS(&raft->vote), r->term, | |
742 | SID_ARGS(&r->sid)); | |
743 | } else { | |
744 | raft->vote = raft->synced_vote = r->sid; | |
745 | return NULL; | |
746 | } | |
747 | break; | |
748 | ||
749 | case RAFT_REC_NOTE: | |
750 | if (!strcmp(r->note, "left")) { | |
751 | return ovsdb_error(NULL, "record %llu indicates server has left " | |
752 | "the cluster; it cannot be added back (use " | |
753 | "\"ovsdb-tool join-cluster\" to add a new " | |
754 | "server)", rec_idx); | |
755 | } | |
756 | return NULL; | |
757 | ||
758 | case RAFT_REC_COMMIT_INDEX: | |
759 | if (r->commit_index < raft->commit_index) { | |
760 | return ovsdb_error(NULL, "record %llu regresses commit index " | |
761 | "from %"PRIu64 " to %"PRIu64, | |
762 | rec_idx, raft->commit_index, r->commit_index); | |
763 | } else if (r->commit_index >= raft->log_end) { | |
764 | return ovsdb_error(NULL, "record %llu advances commit index to " | |
765 | "%"PRIu64 " but last log index is %"PRIu64, | |
766 | rec_idx, r->commit_index, raft->log_end - 1); | |
767 | } else { | |
768 | raft->commit_index = r->commit_index; | |
769 | return NULL; | |
770 | } | |
771 | break; | |
772 | ||
773 | case RAFT_REC_LEADER: | |
774 | /* XXX we could use this to take back leadership for quick restart */ | |
775 | return NULL; | |
776 | ||
777 | default: | |
778 | OVS_NOT_REACHED(); | |
779 | } | |
780 | } | |
781 | ||
782 | static struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
783 | raft_read_header(struct raft *raft) | |
784 | { | |
785 | /* Read header record. */ | |
786 | struct json *json; | |
787 | struct ovsdb_error *error = ovsdb_log_read(raft->log, &json); | |
788 | if (error || !json) { | |
789 | /* Report error or end-of-file. */ | |
790 | return error; | |
791 | } | |
792 | ovsdb_log_mark_base(raft->log); | |
793 | ||
794 | struct raft_header h; | |
795 | error = raft_header_from_json(&h, json); | |
796 | json_destroy(json); | |
797 | if (error) { | |
798 | return error; | |
799 | } | |
800 | ||
801 | raft->sid = h.sid; | |
802 | raft->cid = h.cid; | |
803 | raft->name = xstrdup(h.name); | |
804 | raft->local_address = xstrdup(h.local_address); | |
805 | raft->local_nickname = raft_address_to_nickname(h.local_address, &h.sid); | |
806 | raft->joining = h.joining; | |
807 | ||
808 | if (h.joining) { | |
809 | sset_clone(&raft->remote_addresses, &h.remote_addresses); | |
810 | } else { | |
811 | raft_entry_clone(&raft->snap, &h.snap); | |
812 | raft->log_start = raft->log_end = h.snap_index + 1; | |
813 | raft->commit_index = h.snap_index; | |
814 | raft->last_applied = h.snap_index - 1; | |
815 | } | |
816 | ||
817 | raft_header_uninit(&h); | |
818 | ||
819 | return NULL; | |
820 | } | |
821 | ||
822 | static struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
823 | raft_read_log(struct raft *raft) | |
824 | { | |
825 | for (unsigned long long int i = 1; ; i++) { | |
826 | struct json *json; | |
827 | struct ovsdb_error *error = ovsdb_log_read(raft->log, &json); | |
828 | if (!json) { | |
829 | if (error) { | |
830 | /* We assume that the error is due to a partial write while | |
831 | * appending to the file before a crash, so log it and | |
832 | * continue. */ | |
833 | char *error_string = ovsdb_error_to_string_free(error); | |
834 | VLOG_WARN("%s", error_string); | |
835 | free(error_string); | |
836 | error = NULL; | |
837 | } | |
838 | break; | |
839 | } | |
840 | ||
841 | struct raft_record r; | |
842 | error = raft_record_from_json(&r, json); | |
843 | if (!error) { | |
844 | error = raft_apply_record(raft, i, &r); | |
845 | raft_record_uninit(&r); | |
846 | } | |
847 | if (error) { | |
848 | return ovsdb_wrap_error(error, "error reading record %llu from " | |
849 | "%s log", i, raft->name); | |
850 | } | |
851 | } | |
852 | ||
853 | /* Set the most recent servers. */ | |
854 | raft_get_servers_from_log(raft, VLL_DBG); | |
855 | ||
856 | return NULL; | |
857 | } | |
858 | ||
859 | static void | |
860 | raft_reset_timer(struct raft *raft) | |
861 | { | |
862 | unsigned int duration = (ELECTION_BASE_MSEC | |
863 | + random_range(ELECTION_RANGE_MSEC)); | |
864 | raft->election_base = time_msec(); | |
865 | raft->election_timeout = raft->election_base + duration; | |
866 | } | |
867 | ||
868 | static void | |
869 | raft_add_conn(struct raft *raft, struct jsonrpc_session *js, | |
870 | const struct uuid *sid, bool incoming) | |
871 | { | |
872 | struct raft_conn *conn = xzalloc(sizeof *conn); | |
873 | ovs_list_push_back(&raft->conns, &conn->list_node); | |
874 | conn->js = js; | |
875 | if (sid) { | |
876 | conn->sid = *sid; | |
877 | } | |
878 | conn->nickname = raft_address_to_nickname(jsonrpc_session_get_name(js), | |
879 | &conn->sid); | |
880 | conn->incoming = incoming; | |
881 | conn->js_seqno = jsonrpc_session_get_seqno(conn->js); | |
882 | } | |
883 | ||
884 | /* Starts the local server in an existing Raft cluster, using the local copy of | |
885 | * the cluster's log in 'file_name'. Takes ownership of 'log', whether | |
886 | * successful or not. */ | |
887 | struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
888 | raft_open(struct ovsdb_log *log, struct raft **raftp) | |
889 | { | |
890 | struct raft *raft = raft_alloc(); | |
891 | raft->log = log; | |
892 | ||
893 | struct ovsdb_error *error = raft_read_header(raft); | |
894 | if (error) { | |
895 | goto error; | |
896 | } | |
897 | ||
898 | if (!raft->joining) { | |
899 | error = raft_read_log(raft); | |
900 | if (error) { | |
901 | goto error; | |
902 | } | |
903 | ||
904 | /* Find our own server. */ | |
905 | if (!raft_find_server(raft, &raft->sid)) { | |
906 | error = ovsdb_error(NULL, "server does not belong to cluster"); | |
907 | goto error; | |
908 | } | |
909 | ||
910 | /* If there's only one server, start an election right away so that the | |
911 | * cluster bootstraps quickly. */ | |
912 | if (hmap_count(&raft->servers) == 1) { | |
913 | raft_start_election(raft, false); | |
914 | } | |
915 | } else { | |
916 | raft->join_timeout = time_msec() + 1000; | |
917 | } | |
918 | ||
919 | *raftp = raft; | |
920 | hmap_insert(&all_rafts, &raft->hmap_node, hash_string(raft->name, 0)); | |
921 | return NULL; | |
922 | ||
923 | error: | |
924 | raft_close(raft); | |
925 | *raftp = NULL; | |
926 | return error; | |
927 | } | |
928 | ||
929 | /* Returns the name of 'raft', which in OVSDB is the database schema name. */ | |
930 | const char * | |
931 | raft_get_name(const struct raft *raft) | |
932 | { | |
933 | return raft->name; | |
934 | } | |
935 | ||
936 | /* Returns the cluster ID of 'raft'. If 'raft' has not yet completed joining | |
937 | * its cluster, then 'cid' will be all-zeros (unless the administrator | |
938 | * specified a cluster ID running "ovsdb-tool join-cluster"). | |
939 | * | |
940 | * Each cluster has a unique cluster ID. */ | |
941 | const struct uuid * | |
942 | raft_get_cid(const struct raft *raft) | |
943 | { | |
944 | return &raft->cid; | |
945 | } | |
946 | ||
947 | /* Returns the server ID of 'raft'. Each server has a unique server ID. */ | |
948 | const struct uuid * | |
949 | raft_get_sid(const struct raft *raft) | |
950 | { | |
951 | return &raft->sid; | |
952 | } | |
953 | ||
954 | /* Returns true if 'raft' has completed joining its cluster, has not left or | |
955 | * initiated leaving the cluster, does not have failed disk storage, and is | |
956 | * apparently connected to the leader in a healthy way (or is itself the | |
957 | * leader).*/ | |
958 | bool | |
959 | raft_is_connected(const struct raft *raft) | |
960 | { | |
961 | return (raft->role != RAFT_CANDIDATE | |
962 | && !raft->joining | |
963 | && !raft->leaving | |
964 | && !raft->left | |
965 | && !raft->failed); | |
966 | } | |
967 | ||
968 | /* Returns true if 'raft' is the cluster leader. */ | |
969 | bool | |
970 | raft_is_leader(const struct raft *raft) | |
971 | { | |
972 | return raft->role == RAFT_LEADER; | |
973 | } | |
974 | ||
975 | /* Returns true if 'raft' is the process of joining its cluster. */ | |
976 | bool | |
977 | raft_is_joining(const struct raft *raft) | |
978 | { | |
979 | return raft->joining; | |
980 | } | |
981 | ||
982 | /* Only returns *connected* connections. */ | |
983 | static struct raft_conn * | |
984 | raft_find_conn_by_sid(struct raft *raft, const struct uuid *sid) | |
985 | { | |
986 | if (!uuid_is_zero(sid)) { | |
987 | struct raft_conn *conn; | |
988 | LIST_FOR_EACH (conn, list_node, &raft->conns) { | |
989 | if (uuid_equals(sid, &conn->sid) | |
990 | && jsonrpc_session_is_connected(conn->js)) { | |
991 | return conn; | |
992 | } | |
993 | } | |
994 | } | |
995 | return NULL; | |
996 | } | |
997 | ||
998 | static struct raft_conn * | |
999 | raft_find_conn_by_address(struct raft *raft, const char *address) | |
1000 | { | |
1001 | struct raft_conn *conn; | |
1002 | LIST_FOR_EACH (conn, list_node, &raft->conns) { | |
1003 | if (!strcmp(jsonrpc_session_get_name(conn->js), address)) { | |
1004 | return conn; | |
1005 | } | |
1006 | } | |
1007 | return NULL; | |
1008 | } | |
1009 | ||
1010 | static void OVS_PRINTF_FORMAT(3, 4) | |
1011 | raft_record_note(struct raft *raft, const char *note, | |
1012 | const char *comment_format, ...) | |
1013 | { | |
1014 | va_list args; | |
1015 | va_start(args, comment_format); | |
1016 | char *comment = xvasprintf(comment_format, args); | |
1017 | va_end(args); | |
1018 | ||
1019 | struct raft_record r = { | |
1020 | .type = RAFT_REC_NOTE, | |
1021 | .comment = comment, | |
1022 | .note = CONST_CAST(char *, note), | |
1023 | }; | |
1024 | ignore(ovsdb_log_write_and_free(raft->log, raft_record_to_json(&r))); | |
1025 | ||
1026 | free(comment); | |
1027 | } | |
1028 | ||
1029 | /* If we're leader, try to transfer leadership to another server, logging | |
1030 | * 'reason' as the human-readable reason (it should be a phrase suitable for | |
1031 | * following "because") . */ | |
1032 | void | |
1033 | raft_transfer_leadership(struct raft *raft, const char *reason) | |
1034 | { | |
1035 | if (raft->role != RAFT_LEADER) { | |
1036 | return; | |
1037 | } | |
1038 | ||
1039 | struct raft_server *s; | |
1040 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
1041 | if (!uuid_equals(&raft->sid, &s->sid) | |
1042 | && s->phase == RAFT_PHASE_STABLE) { | |
1043 | struct raft_conn *conn = raft_find_conn_by_sid(raft, &s->sid); | |
1044 | if (!conn) { | |
1045 | continue; | |
1046 | } | |
1047 | ||
1048 | union raft_rpc rpc = { | |
1049 | .become_leader = { | |
1050 | .common = { | |
1051 | .comment = CONST_CAST(char *, reason), | |
1052 | .type = RAFT_RPC_BECOME_LEADER, | |
1053 | .sid = s->sid, | |
1054 | }, | |
1055 | .term = raft->term, | |
1056 | } | |
1057 | }; | |
1058 | raft_send__(raft, &rpc, conn); | |
1059 | ||
1060 | raft_record_note(raft, "transfer leadership", | |
1061 | "transferring leadership to %s because %s", | |
1062 | s->nickname, reason); | |
1063 | break; | |
1064 | } | |
1065 | } | |
1066 | } | |
1067 | ||
1068 | /* Send a RemoveServerRequest to the rest of the servers in the cluster. | |
1069 | * | |
1070 | * If we know which server is the leader, we can just send the request to it. | |
1071 | * However, we might not know which server is the leader, and we might never | |
1072 | * find out if the remove request was actually previously committed by a | |
1073 | * majority of the servers (because in that case the new leader will not send | |
1074 | * AppendRequests or heartbeats to us). Therefore, we instead send | |
1075 | * RemoveRequests to every server. This theoretically has the same problem, if | |
1076 | * the current cluster leader was not previously a member of the cluster, but | |
1077 | * it seems likely to be more robust in practice. */ | |
1078 | static void | |
1079 | raft_send_remove_server_requests(struct raft *raft) | |
1080 | { | |
1081 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
1082 | VLOG_INFO_RL(&rl, "sending remove request (joining=%s, leaving=%s)", | |
1083 | raft->joining ? "true" : "false", | |
1084 | raft->leaving ? "true" : "false"); | |
1085 | const struct raft_server *s; | |
1086 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
1087 | if (!uuid_equals(&s->sid, &raft->sid)) { | |
1088 | union raft_rpc rpc = (union raft_rpc) { | |
1089 | .remove_server_request = { | |
1090 | .common = { | |
1091 | .type = RAFT_RPC_REMOVE_SERVER_REQUEST, | |
1092 | .sid = s->sid, | |
1093 | }, | |
1094 | .sid = raft->sid, | |
1095 | }, | |
1096 | }; | |
1097 | raft_send(raft, &rpc); | |
1098 | } | |
1099 | } | |
1100 | ||
1101 | raft->leave_timeout = time_msec() + ELECTION_BASE_MSEC; | |
1102 | } | |
1103 | ||
1104 | /* Attempts to start 'raft' leaving its cluster. The caller can check progress | |
1105 | * using raft_is_leaving() and raft_left(). */ | |
1106 | void | |
1107 | raft_leave(struct raft *raft) | |
1108 | { | |
1109 | if (raft->joining || raft->failed || raft->leaving || raft->left) { | |
1110 | return; | |
1111 | } | |
1112 | VLOG_INFO(SID_FMT": starting to leave cluster "CID_FMT, | |
1113 | SID_ARGS(&raft->sid), CID_ARGS(&raft->cid)); | |
1114 | raft->leaving = true; | |
1115 | raft_transfer_leadership(raft, "this server is leaving the cluster"); | |
1116 | raft_become_follower(raft); | |
1117 | raft_send_remove_server_requests(raft); | |
1118 | raft->leave_timeout = time_msec() + ELECTION_BASE_MSEC; | |
1119 | } | |
1120 | ||
1121 | /* Returns true if 'raft' is currently attempting to leave its cluster. */ | |
1122 | bool | |
1123 | raft_is_leaving(const struct raft *raft) | |
1124 | { | |
1125 | return raft->leaving; | |
1126 | } | |
1127 | ||
1128 | /* Returns true if 'raft' successfully left its cluster. */ | |
1129 | bool | |
1130 | raft_left(const struct raft *raft) | |
1131 | { | |
1132 | return raft->left; | |
1133 | } | |
1134 | ||
1135 | /* Returns true if 'raft' has experienced a disk I/O failure. When this | |
1136 | * returns true, only closing and reopening 'raft' allows for recovery. */ | |
1137 | bool | |
1138 | raft_failed(const struct raft *raft) | |
1139 | { | |
1140 | return raft->failed; | |
1141 | } | |
1142 | ||
1143 | /* Forces 'raft' to attempt to take leadership of the cluster by deposing the | |
1144 | * current cluster. */ | |
1145 | void | |
1146 | raft_take_leadership(struct raft *raft) | |
1147 | { | |
1148 | if (raft->role != RAFT_LEADER) { | |
1149 | raft_start_election(raft, true); | |
1150 | } | |
1151 | } | |
1152 | ||
1153 | /* Closes everything owned by 'raft' that might be visible outside the process: | |
1154 | * network connections, commands, etc. This is part of closing 'raft'; it is | |
1155 | * also used if 'raft' has failed in an unrecoverable way. */ | |
1156 | static void | |
1157 | raft_close__(struct raft *raft) | |
1158 | { | |
1159 | if (!hmap_node_is_null(&raft->hmap_node)) { | |
1160 | hmap_remove(&all_rafts, &raft->hmap_node); | |
1161 | hmap_node_nullify(&raft->hmap_node); | |
1162 | } | |
1163 | ||
1164 | raft_complete_all_commands(raft, RAFT_CMD_SHUTDOWN); | |
1165 | ||
1166 | struct raft_server *rs = raft->remove_server; | |
1167 | if (rs) { | |
1168 | raft_send_remove_server_reply__(raft, &rs->sid, &rs->requester_sid, | |
1169 | rs->requester_conn, false, | |
1170 | RAFT_SERVER_SHUTDOWN); | |
1171 | raft_server_destroy(raft->remove_server); | |
1172 | raft->remove_server = NULL; | |
1173 | } | |
1174 | ||
1175 | struct raft_conn *conn, *next; | |
1176 | LIST_FOR_EACH_SAFE (conn, next, list_node, &raft->conns) { | |
1177 | raft_conn_close(conn); | |
1178 | } | |
1179 | } | |
1180 | ||
1181 | /* Closes and frees 'raft'. | |
1182 | * | |
1183 | * A server's cluster membership is independent of whether the server is | |
1184 | * actually running. When a server that is a member of a cluster closes, the | |
1185 | * cluster treats this as a server failure. */ | |
1186 | void | |
1187 | raft_close(struct raft *raft) | |
1188 | { | |
1189 | if (!raft) { | |
1190 | return; | |
1191 | } | |
1192 | ||
1193 | raft_transfer_leadership(raft, "this server is shutting down"); | |
1194 | ||
1195 | raft_close__(raft); | |
1196 | ||
1197 | ovsdb_log_close(raft->log); | |
1198 | ||
1199 | raft_servers_destroy(&raft->servers); | |
1200 | ||
1201 | for (uint64_t index = raft->log_start; index < raft->log_end; index++) { | |
1202 | struct raft_entry *e = &raft->entries[index - raft->log_start]; | |
1203 | raft_entry_uninit(e); | |
1204 | } | |
1205 | free(raft->entries); | |
1206 | ||
1207 | raft_entry_uninit(&raft->snap); | |
1208 | ||
1209 | raft_waiters_destroy(raft); | |
1210 | ||
1211 | raft_servers_destroy(&raft->add_servers); | |
1212 | ||
1213 | hmap_destroy(&raft->commands); | |
1214 | ||
1215 | pstream_close(raft->listener); | |
1216 | ||
1217 | sset_destroy(&raft->remote_addresses); | |
1218 | free(raft->local_address); | |
1219 | free(raft->local_nickname); | |
1220 | free(raft->name); | |
1221 | ||
1222 | free(raft); | |
1223 | } | |
1224 | ||
1225 | static bool | |
1226 | raft_conn_receive(struct raft *raft, struct raft_conn *conn, | |
1227 | union raft_rpc *rpc) | |
1228 | { | |
1229 | struct jsonrpc_msg *msg = jsonrpc_session_recv(conn->js); | |
1230 | if (!msg) { | |
1231 | return false; | |
1232 | } | |
1233 | ||
1234 | struct ovsdb_error *error = raft_rpc_from_jsonrpc(&raft->cid, &raft->sid, | |
1235 | msg, rpc); | |
1236 | jsonrpc_msg_destroy(msg); | |
1237 | if (error) { | |
1238 | char *s = ovsdb_error_to_string_free(error); | |
1239 | VLOG_INFO("%s: %s", jsonrpc_session_get_name(conn->js), s); | |
1240 | free(s); | |
1241 | return false; | |
1242 | } | |
1243 | ||
1244 | if (uuid_is_zero(&conn->sid)) { | |
1245 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(50, 50); | |
1246 | conn->sid = rpc->common.sid; | |
1247 | VLOG_INFO_RL(&rl, "%s: learned server ID "SID_FMT, | |
1248 | jsonrpc_session_get_name(conn->js), SID_ARGS(&conn->sid)); | |
1249 | } else if (!uuid_equals(&conn->sid, &rpc->common.sid)) { | |
1250 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5); | |
1251 | VLOG_WARN_RL(&rl, "%s: ignoring message with unexpected server ID " | |
1252 | SID_FMT" (expected "SID_FMT")", | |
1253 | jsonrpc_session_get_name(conn->js), | |
1254 | SID_ARGS(&rpc->common.sid), SID_ARGS(&conn->sid)); | |
1255 | raft_rpc_uninit(rpc); | |
1256 | return false; | |
1257 | } | |
1258 | ||
1259 | const char *address = (rpc->type == RAFT_RPC_HELLO_REQUEST | |
1260 | ? rpc->hello_request.address | |
1261 | : rpc->type == RAFT_RPC_ADD_SERVER_REQUEST | |
1262 | ? rpc->add_server_request.address | |
1263 | : NULL); | |
1264 | if (address) { | |
1265 | char *new_nickname = raft_address_to_nickname(address, &conn->sid); | |
1266 | if (strcmp(conn->nickname, new_nickname)) { | |
1267 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(50, 50); | |
1268 | VLOG_INFO_RL(&rl, "%s: learned remote address %s", | |
1269 | jsonrpc_session_get_name(conn->js), address); | |
1270 | ||
1271 | free(conn->nickname); | |
1272 | conn->nickname = new_nickname; | |
1273 | } else { | |
1274 | free(new_nickname); | |
1275 | } | |
1276 | } | |
1277 | ||
1278 | return true; | |
1279 | } | |
1280 | ||
1281 | static const char * | |
1282 | raft_get_nickname(const struct raft *raft, const struct uuid *sid, | |
1283 | char buf[SID_LEN + 1], size_t bufsize) | |
1284 | { | |
1285 | if (uuid_equals(sid, &raft->sid)) { | |
1286 | return raft->local_nickname; | |
1287 | } | |
1288 | ||
1289 | const char *s = raft_servers_get_nickname__(&raft->servers, sid); | |
1290 | if (s) { | |
1291 | return s; | |
1292 | } | |
1293 | ||
1294 | return raft_servers_get_nickname(&raft->add_servers, sid, buf, bufsize); | |
1295 | } | |
1296 | ||
1297 | static void | |
1298 | log_rpc(const union raft_rpc *rpc, | |
1299 | const char *direction, const struct raft_conn *conn) | |
1300 | { | |
1301 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(600, 600); | |
1302 | if (!raft_rpc_is_heartbeat(rpc) && !VLOG_DROP_DBG(&rl)) { | |
1303 | struct ds s = DS_EMPTY_INITIALIZER; | |
1304 | raft_rpc_format(rpc, &s); | |
1305 | VLOG_DBG("%s%s %s", direction, conn->nickname, ds_cstr(&s)); | |
1306 | ds_destroy(&s); | |
1307 | } | |
1308 | } | |
1309 | ||
1310 | static void | |
1311 | raft_send_add_server_request(struct raft *raft, struct raft_conn *conn) | |
1312 | { | |
1313 | union raft_rpc rq = { | |
1314 | .add_server_request = { | |
1315 | .common = { | |
1316 | .type = RAFT_RPC_ADD_SERVER_REQUEST, | |
1317 | .sid = UUID_ZERO, | |
1318 | .comment = NULL, | |
1319 | }, | |
1320 | .address = raft->local_address, | |
1321 | }, | |
1322 | }; | |
1323 | raft_send__(raft, &rq, conn); | |
1324 | } | |
1325 | ||
1326 | static void | |
1327 | raft_conn_run(struct raft *raft, struct raft_conn *conn) | |
1328 | { | |
1329 | jsonrpc_session_run(conn->js); | |
1330 | ||
1331 | unsigned int new_seqno = jsonrpc_session_get_seqno(conn->js); | |
1332 | bool just_connected = (new_seqno != conn->js_seqno | |
1333 | && jsonrpc_session_is_connected(conn->js)); | |
1334 | conn->js_seqno = new_seqno; | |
1335 | if (just_connected) { | |
1336 | if (raft->joining) { | |
1337 | raft_send_add_server_request(raft, conn); | |
1338 | } else if (raft->leaving) { | |
1339 | union raft_rpc rq = { | |
1340 | .remove_server_request = { | |
1341 | .common = { | |
1342 | .type = RAFT_RPC_REMOVE_SERVER_REQUEST, | |
1343 | .sid = conn->sid, | |
1344 | }, | |
1345 | .sid = raft->sid, | |
1346 | }, | |
1347 | }; | |
1348 | raft_send__(raft, &rq, conn); | |
1349 | } else { | |
1350 | union raft_rpc rq = (union raft_rpc) { | |
1351 | .hello_request = { | |
1352 | .common = { | |
1353 | .type = RAFT_RPC_HELLO_REQUEST, | |
1354 | .sid = conn->sid, | |
1355 | }, | |
1356 | .address = raft->local_address, | |
1357 | }, | |
1358 | }; | |
1359 | raft_send__(raft, &rq, conn); | |
1360 | } | |
1361 | } | |
1362 | ||
1363 | for (size_t i = 0; i < 50; i++) { | |
1364 | union raft_rpc rpc; | |
1365 | if (!raft_conn_receive(raft, conn, &rpc)) { | |
1366 | break; | |
1367 | } | |
1368 | ||
1369 | log_rpc(&rpc, "<--", conn); | |
1370 | raft_handle_rpc(raft, &rpc); | |
1371 | raft_rpc_uninit(&rpc); | |
1372 | } | |
1373 | } | |
1374 | ||
1375 | static void | |
1376 | raft_waiter_complete_rpc(struct raft *raft, const union raft_rpc *rpc) | |
1377 | { | |
1378 | uint64_t term = raft_rpc_get_term(rpc); | |
1379 | if (term && term < raft->term) { | |
1380 | /* Drop the message because it's for an expired term. */ | |
1381 | return; | |
1382 | } | |
1383 | ||
1384 | if (!raft_is_rpc_synced(raft, rpc)) { | |
1385 | /* This is a bug. A reply message is deferred because some state in | |
1386 | * the message, such as a term or index, has not been committed to | |
1387 | * disk, and they should only be completed when that commit is done. | |
1388 | * But this message is being completed before the commit is finished. | |
1389 | * Complain, and hope that someone reports the bug. */ | |
1390 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
1391 | if (VLOG_DROP_ERR(&rl)) { | |
1392 | return; | |
1393 | } | |
1394 | ||
1395 | struct ds s = DS_EMPTY_INITIALIZER; | |
1396 | ||
1397 | if (term > raft->synced_term) { | |
1398 | ds_put_format(&s, " because message term %"PRIu64" is " | |
1399 | "past synced term %"PRIu64, | |
1400 | term, raft->synced_term); | |
1401 | } | |
1402 | ||
1403 | uint64_t index = raft_rpc_get_min_sync_index(rpc); | |
1404 | if (index > raft->log_synced) { | |
1405 | ds_put_format(&s, " %s message index %"PRIu64" is past last " | |
1406 | "synced index %"PRIu64, | |
1407 | s.length ? "and" : "because", | |
1408 | index, raft->log_synced); | |
1409 | } | |
1410 | ||
1411 | const struct uuid *vote = raft_rpc_get_vote(rpc); | |
1412 | if (vote && !uuid_equals(vote, &raft->synced_vote)) { | |
1413 | char buf1[SID_LEN + 1]; | |
1414 | char buf2[SID_LEN + 1]; | |
1415 | ds_put_format(&s, " %s vote %s differs from synced vote %s", | |
1416 | s.length ? "and" : "because", | |
1417 | raft_get_nickname(raft, vote, buf1, sizeof buf1), | |
1418 | raft_get_nickname(raft, &raft->synced_vote, | |
1419 | buf2, sizeof buf2)); | |
1420 | } | |
1421 | ||
1422 | char buf[SID_LEN + 1]; | |
1423 | ds_put_format(&s, ": %s ", | |
1424 | raft_get_nickname(raft, &rpc->common.sid, | |
1425 | buf, sizeof buf)); | |
1426 | raft_rpc_format(rpc, &s); | |
1427 | VLOG_ERR("internal error: deferred %s message completed " | |
1428 | "but not ready to send%s", | |
1429 | raft_rpc_type_to_string(rpc->type), ds_cstr(&s)); | |
1430 | ds_destroy(&s); | |
1431 | ||
1432 | return; | |
1433 | } | |
1434 | ||
1435 | struct raft_conn *dst = raft_find_conn_by_sid(raft, &rpc->common.sid); | |
1436 | if (dst) { | |
1437 | raft_send__(raft, rpc, dst); | |
1438 | } | |
1439 | } | |
1440 | ||
1441 | static void | |
1442 | raft_waiter_complete(struct raft *raft, struct raft_waiter *w) | |
1443 | { | |
1444 | switch (w->type) { | |
1445 | case RAFT_W_ENTRY: | |
1446 | if (raft->role == RAFT_LEADER) { | |
1447 | raft_update_our_match_index(raft, w->entry.index); | |
1448 | } | |
1449 | raft->log_synced = w->entry.index; | |
1450 | break; | |
1451 | ||
1452 | case RAFT_W_TERM: | |
1453 | raft->synced_term = w->term.term; | |
1454 | raft->synced_vote = w->term.vote; | |
1455 | break; | |
1456 | ||
1457 | case RAFT_W_RPC: | |
1458 | raft_waiter_complete_rpc(raft, w->rpc); | |
1459 | break; | |
1460 | } | |
1461 | } | |
1462 | ||
1463 | static void | |
1464 | raft_waiter_destroy(struct raft_waiter *w) | |
1465 | { | |
1466 | if (!w) { | |
1467 | return; | |
1468 | } | |
1469 | ||
1470 | ovs_list_remove(&w->list_node); | |
1471 | ||
1472 | switch (w->type) { | |
1473 | case RAFT_W_ENTRY: | |
1474 | case RAFT_W_TERM: | |
1475 | break; | |
1476 | ||
1477 | case RAFT_W_RPC: | |
1478 | raft_rpc_uninit(w->rpc); | |
1479 | free(w->rpc); | |
1480 | break; | |
1481 | } | |
1482 | free(w); | |
1483 | } | |
1484 | ||
1485 | static void | |
1486 | raft_waiters_run(struct raft *raft) | |
1487 | { | |
1488 | if (ovs_list_is_empty(&raft->waiters)) { | |
1489 | return; | |
1490 | } | |
1491 | ||
1492 | uint64_t cur = ovsdb_log_commit_progress(raft->log); | |
1493 | struct raft_waiter *w, *next; | |
1494 | LIST_FOR_EACH_SAFE (w, next, list_node, &raft->waiters) { | |
1495 | if (cur < w->commit_ticket) { | |
1496 | break; | |
1497 | } | |
1498 | raft_waiter_complete(raft, w); | |
1499 | raft_waiter_destroy(w); | |
1500 | } | |
1501 | } | |
1502 | ||
1503 | static void | |
1504 | raft_waiters_wait(struct raft *raft) | |
1505 | { | |
1506 | struct raft_waiter *w; | |
1507 | LIST_FOR_EACH (w, list_node, &raft->waiters) { | |
1508 | ovsdb_log_commit_wait(raft->log, w->commit_ticket); | |
1509 | break; | |
1510 | } | |
1511 | } | |
1512 | ||
1513 | static void | |
1514 | raft_waiters_destroy(struct raft *raft) | |
1515 | { | |
1516 | struct raft_waiter *w, *next; | |
1517 | LIST_FOR_EACH_SAFE (w, next, list_node, &raft->waiters) { | |
1518 | raft_waiter_destroy(w); | |
1519 | } | |
1520 | } | |
1521 | ||
1522 | static bool OVS_WARN_UNUSED_RESULT | |
1523 | raft_set_term(struct raft *raft, uint64_t term, const struct uuid *vote) | |
1524 | { | |
1525 | struct ovsdb_error *error = raft_write_state(raft->log, term, vote); | |
1526 | if (!raft_handle_write_error(raft, error)) { | |
1527 | return false; | |
1528 | } | |
1529 | ||
1530 | struct raft_waiter *w = raft_waiter_create(raft, RAFT_W_TERM, true); | |
1531 | raft->term = w->term.term = term; | |
1532 | raft->vote = w->term.vote = vote ? *vote : UUID_ZERO; | |
1533 | return true; | |
1534 | } | |
1535 | ||
1536 | static void | |
1537 | raft_accept_vote(struct raft *raft, struct raft_server *s, | |
1538 | const struct uuid *vote) | |
1539 | { | |
1540 | if (uuid_equals(&s->vote, vote)) { | |
1541 | return; | |
1542 | } | |
1543 | if (!uuid_is_zero(&s->vote)) { | |
1544 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 1); | |
1545 | char buf1[SID_LEN + 1]; | |
1546 | char buf2[SID_LEN + 1]; | |
1547 | VLOG_WARN_RL(&rl, "server %s changed its vote from %s to %s", | |
1548 | s->nickname, | |
1549 | raft_get_nickname(raft, &s->vote, buf1, sizeof buf1), | |
1550 | raft_get_nickname(raft, vote, buf2, sizeof buf2)); | |
1551 | } | |
1552 | s->vote = *vote; | |
1553 | if (uuid_equals(vote, &raft->sid) | |
1554 | && ++raft->n_votes > hmap_count(&raft->servers) / 2) { | |
1555 | raft_become_leader(raft); | |
1556 | } | |
1557 | } | |
1558 | ||
1559 | static void | |
1560 | raft_start_election(struct raft *raft, bool leadership_transfer) | |
1561 | { | |
1562 | if (raft->leaving) { | |
1563 | return; | |
1564 | } | |
1565 | ||
1566 | struct raft_server *me = raft_find_server(raft, &raft->sid); | |
1567 | if (!me) { | |
1568 | return; | |
1569 | } | |
1570 | ||
1571 | if (!raft_set_term(raft, raft->term + 1, &raft->sid)) { | |
1572 | return; | |
1573 | } | |
1574 | ||
1575 | raft_complete_all_commands(raft, RAFT_CMD_LOST_LEADERSHIP); | |
1576 | ||
1577 | ovs_assert(raft->role != RAFT_LEADER); | |
1578 | ovs_assert(hmap_is_empty(&raft->commands)); | |
1579 | raft->role = RAFT_CANDIDATE; | |
1580 | ||
1581 | raft->n_votes = 0; | |
1582 | ||
1583 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5); | |
1584 | if (!VLOG_DROP_INFO(&rl)) { | |
1585 | long long int now = time_msec(); | |
1586 | if (now >= raft->election_timeout) { | |
1587 | VLOG_INFO("term %"PRIu64": %lld ms timeout expired, " | |
1588 | "starting election", | |
1589 | raft->term, now - raft->election_base); | |
1590 | } else { | |
1591 | VLOG_INFO("term %"PRIu64": starting election", raft->term); | |
1592 | } | |
1593 | } | |
1594 | raft_reset_timer(raft); | |
1595 | ||
1596 | struct raft_server *peer; | |
1597 | HMAP_FOR_EACH (peer, hmap_node, &raft->servers) { | |
1598 | peer->vote = UUID_ZERO; | |
1599 | if (uuid_equals(&raft->sid, &peer->sid)) { | |
1600 | continue; | |
1601 | } | |
1602 | ||
1603 | union raft_rpc rq = { | |
1604 | .vote_request = { | |
1605 | .common = { | |
1606 | .type = RAFT_RPC_VOTE_REQUEST, | |
1607 | .sid = peer->sid, | |
1608 | }, | |
1609 | .term = raft->term, | |
1610 | .last_log_index = raft->log_end - 1, | |
1611 | .last_log_term = ( | |
1612 | raft->log_end > raft->log_start | |
1613 | ? raft->entries[raft->log_end - raft->log_start - 1].term | |
1614 | : raft->snap.term), | |
1615 | .leadership_transfer = leadership_transfer, | |
1616 | }, | |
1617 | }; | |
1618 | raft_send(raft, &rq); | |
1619 | } | |
1620 | ||
1621 | /* Vote for ourselves. */ | |
1622 | raft_accept_vote(raft, me, &raft->sid); | |
1623 | } | |
1624 | ||
1625 | static void | |
1626 | raft_open_conn(struct raft *raft, const char *address, const struct uuid *sid) | |
1627 | { | |
1628 | if (strcmp(address, raft->local_address) | |
1629 | && !raft_find_conn_by_address(raft, address)) { | |
1630 | raft_add_conn(raft, jsonrpc_session_open(address, true), sid, false); | |
1631 | } | |
1632 | } | |
1633 | ||
1634 | static void | |
1635 | raft_conn_close(struct raft_conn *conn) | |
1636 | { | |
1637 | jsonrpc_session_close(conn->js); | |
1638 | ovs_list_remove(&conn->list_node); | |
1639 | free(conn->nickname); | |
1640 | free(conn); | |
1641 | } | |
1642 | ||
1643 | /* Returns true if 'conn' should stay open, false if it should be closed. */ | |
1644 | static bool | |
1645 | raft_conn_should_stay_open(struct raft *raft, struct raft_conn *conn) | |
1646 | { | |
1647 | /* Close the connection if it's actually dead. If necessary, we'll | |
1648 | * initiate a new session later. */ | |
1649 | if (!jsonrpc_session_is_alive(conn->js)) { | |
1650 | return false; | |
1651 | } | |
1652 | ||
1653 | /* Keep incoming sessions. We trust the originator to decide to drop | |
1654 | * it. */ | |
1655 | if (conn->incoming) { | |
1656 | return true; | |
1657 | } | |
1658 | ||
1659 | /* If we are joining the cluster, keep sessions to the remote addresses | |
1660 | * that are supposed to be part of the cluster we're joining. */ | |
1661 | if (raft->joining && sset_contains(&raft->remote_addresses, | |
1662 | jsonrpc_session_get_name(conn->js))) { | |
1663 | return true; | |
1664 | } | |
1665 | ||
1666 | /* We have joined the cluster. If we did that "recently", then there is a | |
1667 | * chance that we do not have the most recent server configuration log | |
1668 | * entry. If so, it's a waste to disconnect from the servers that were in | |
1669 | * remote_addresses and that will probably appear in the configuration, | |
1670 | * just to reconnect to them a moment later when we do get the | |
1671 | * configuration update. If we are not ourselves in the configuration, | |
1672 | * then we know that there must be a new configuration coming up, so in | |
1673 | * that case keep the connection. */ | |
1674 | if (!raft_find_server(raft, &raft->sid)) { | |
1675 | return true; | |
1676 | } | |
1677 | ||
1678 | /* Keep the connection only if the server is part of the configuration. */ | |
1679 | return raft_find_server(raft, &conn->sid); | |
1680 | } | |
1681 | ||
1682 | /* Allows 'raft' to maintain the distributed log. Call this function as part | |
1683 | * of the process's main loop. */ | |
1684 | void | |
1685 | raft_run(struct raft *raft) | |
1686 | { | |
1687 | if (raft->left || raft->failed) { | |
1688 | return; | |
1689 | } | |
1690 | ||
1691 | raft_waiters_run(raft); | |
1692 | ||
1693 | if (!raft->listener && time_msec() >= raft->listen_backoff) { | |
1694 | char *paddr = raft_make_address_passive(raft->local_address); | |
1695 | int error = pstream_open(paddr, &raft->listener, DSCP_DEFAULT); | |
1696 | if (error) { | |
1697 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5); | |
1698 | VLOG_WARN_RL(&rl, "%s: listen failed (%s)", | |
1699 | paddr, ovs_strerror(error)); | |
1700 | raft->listen_backoff = time_msec() + 1000; | |
1701 | } | |
1702 | free(paddr); | |
1703 | } | |
1704 | ||
1705 | if (raft->listener) { | |
1706 | struct stream *stream; | |
1707 | int error = pstream_accept(raft->listener, &stream); | |
1708 | if (!error) { | |
1709 | raft_add_conn(raft, jsonrpc_session_open_unreliably( | |
1710 | jsonrpc_open(stream), DSCP_DEFAULT), NULL, | |
1711 | true); | |
1712 | } else if (error != EAGAIN) { | |
1713 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 1); | |
1714 | VLOG_WARN_RL(&rl, "%s: accept failed: %s", | |
1715 | pstream_get_name(raft->listener), | |
1716 | ovs_strerror(error)); | |
1717 | } | |
1718 | } | |
1719 | ||
1720 | /* Run RPCs for all open sessions. */ | |
1721 | struct raft_conn *conn; | |
1722 | LIST_FOR_EACH (conn, list_node, &raft->conns) { | |
1723 | raft_conn_run(raft, conn); | |
1724 | } | |
1725 | ||
1726 | /* Close unneeded sessions. */ | |
1727 | struct raft_conn *next; | |
1728 | LIST_FOR_EACH_SAFE (conn, next, list_node, &raft->conns) { | |
1729 | if (!raft_conn_should_stay_open(raft, conn)) { | |
1730 | raft_conn_close(conn); | |
1731 | } | |
1732 | } | |
1733 | ||
1734 | /* Open needed sessions. */ | |
1735 | struct raft_server *server; | |
1736 | HMAP_FOR_EACH (server, hmap_node, &raft->servers) { | |
1737 | raft_open_conn(raft, server->address, &server->sid); | |
1738 | } | |
1739 | if (raft->joining) { | |
1740 | const char *address; | |
1741 | SSET_FOR_EACH (address, &raft->remote_addresses) { | |
1742 | raft_open_conn(raft, address, NULL); | |
1743 | } | |
1744 | } | |
1745 | ||
1746 | if (!raft->joining && time_msec() >= raft->election_timeout) { | |
1747 | raft_start_election(raft, false); | |
1748 | } | |
1749 | ||
1750 | if (raft->leaving && time_msec() >= raft->leave_timeout) { | |
1751 | raft_send_remove_server_requests(raft); | |
1752 | } | |
1753 | ||
1754 | if (raft->joining && time_msec() >= raft->join_timeout) { | |
1755 | raft->join_timeout = time_msec() + 1000; | |
1756 | LIST_FOR_EACH (conn, list_node, &raft->conns) { | |
1757 | raft_send_add_server_request(raft, conn); | |
1758 | } | |
1759 | } | |
1760 | ||
1761 | if (time_msec() >= raft->ping_timeout) { | |
1762 | if (raft->role == RAFT_LEADER) { | |
1763 | raft_send_heartbeats(raft); | |
1764 | } else { | |
1765 | long long int now = time_msec(); | |
1766 | struct raft_command *cmd, *next_cmd; | |
1767 | HMAP_FOR_EACH_SAFE (cmd, next_cmd, hmap_node, &raft->commands) { | |
1768 | if (cmd->timestamp | |
1769 | && now - cmd->timestamp > ELECTION_BASE_MSEC) { | |
1770 | raft_command_complete(raft, cmd, RAFT_CMD_TIMEOUT); | |
1771 | } | |
1772 | } | |
1773 | } | |
1774 | raft->ping_timeout = time_msec() + PING_TIME_MSEC; | |
1775 | } | |
1776 | ||
1777 | /* Do this only at the end; if we did it as soon as we set raft->left or | |
1778 | * raft->failed in handling the RemoveServerReply, then it could easily | |
1779 | * cause references to freed memory in RPC sessions, etc. */ | |
1780 | if (raft->left || raft->failed) { | |
1781 | raft_close__(raft); | |
1782 | } | |
1783 | } | |
1784 | ||
1785 | static void | |
1786 | raft_wait_session(struct jsonrpc_session *js) | |
1787 | { | |
1788 | if (js) { | |
1789 | jsonrpc_session_wait(js); | |
1790 | jsonrpc_session_recv_wait(js); | |
1791 | } | |
1792 | } | |
1793 | ||
1794 | /* Causes the next call to poll_block() to wake up when 'raft' needs to do | |
1795 | * something. */ | |
1796 | void | |
1797 | raft_wait(struct raft *raft) | |
1798 | { | |
1799 | if (raft->left || raft->failed) { | |
1800 | return; | |
1801 | } | |
1802 | ||
1803 | raft_waiters_wait(raft); | |
1804 | ||
1805 | if (raft->listener) { | |
1806 | pstream_wait(raft->listener); | |
1807 | } else { | |
1808 | poll_timer_wait_until(raft->listen_backoff); | |
1809 | } | |
1810 | ||
1811 | struct raft_conn *conn; | |
1812 | LIST_FOR_EACH (conn, list_node, &raft->conns) { | |
1813 | raft_wait_session(conn->js); | |
1814 | } | |
1815 | ||
1816 | if (!raft->joining) { | |
1817 | poll_timer_wait_until(raft->election_timeout); | |
1818 | } else { | |
1819 | poll_timer_wait_until(raft->join_timeout); | |
1820 | } | |
1821 | if (raft->leaving) { | |
1822 | poll_timer_wait_until(raft->leave_timeout); | |
1823 | } | |
1824 | if (raft->role == RAFT_LEADER || !hmap_is_empty(&raft->commands)) { | |
1825 | poll_timer_wait_until(raft->ping_timeout); | |
1826 | } | |
1827 | } | |
1828 | ||
1829 | static struct raft_waiter * | |
1830 | raft_waiter_create(struct raft *raft, enum raft_waiter_type type, | |
1831 | bool start_commit) | |
1832 | { | |
1833 | struct raft_waiter *w = xzalloc(sizeof *w); | |
1834 | ovs_list_push_back(&raft->waiters, &w->list_node); | |
1835 | w->commit_ticket = start_commit ? ovsdb_log_commit_start(raft->log) : 0; | |
1836 | w->type = type; | |
1837 | return w; | |
1838 | } | |
1839 | ||
1840 | /* Returns a human-readable representation of 'status' (or NULL if 'status' is | |
1841 | * invalid). */ | |
1842 | const char * | |
1843 | raft_command_status_to_string(enum raft_command_status status) | |
1844 | { | |
1845 | switch (status) { | |
1846 | case RAFT_CMD_INCOMPLETE: | |
1847 | return "operation still in progress"; | |
1848 | case RAFT_CMD_SUCCESS: | |
1849 | return "success"; | |
1850 | case RAFT_CMD_NOT_LEADER: | |
1851 | return "not leader"; | |
1852 | case RAFT_CMD_BAD_PREREQ: | |
1853 | return "prerequisite check failed"; | |
1854 | case RAFT_CMD_LOST_LEADERSHIP: | |
1855 | return "lost leadership"; | |
1856 | case RAFT_CMD_SHUTDOWN: | |
1857 | return "server shutdown"; | |
1858 | case RAFT_CMD_IO_ERROR: | |
1859 | return "I/O error"; | |
1860 | case RAFT_CMD_TIMEOUT: | |
1861 | return "timeout"; | |
1862 | default: | |
1863 | return NULL; | |
1864 | } | |
1865 | } | |
1866 | ||
1867 | /* Converts human-readable status in 's' into status code in '*statusp'. | |
1868 | * Returns true if successful, false if 's' is unknown. */ | |
1869 | bool | |
1870 | raft_command_status_from_string(const char *s, | |
1871 | enum raft_command_status *statusp) | |
1872 | { | |
1873 | for (enum raft_command_status status = 0; ; status++) { | |
1874 | const char *s2 = raft_command_status_to_string(status); | |
1875 | if (!s2) { | |
1876 | *statusp = 0; | |
1877 | return false; | |
1878 | } else if (!strcmp(s, s2)) { | |
1879 | *statusp = status; | |
1880 | return true; | |
1881 | } | |
1882 | } | |
1883 | } | |
1884 | ||
1885 | static const struct uuid * | |
1886 | raft_get_eid(const struct raft *raft, uint64_t index) | |
1887 | { | |
1888 | for (; index >= raft->log_start; index--) { | |
1889 | const struct raft_entry *e = raft_get_entry(raft, index); | |
1890 | if (e->data) { | |
1891 | return &e->eid; | |
1892 | } | |
1893 | } | |
1894 | return &raft->snap.eid; | |
1895 | } | |
1896 | ||
1897 | static const struct uuid * | |
1898 | raft_current_eid(const struct raft *raft) | |
1899 | { | |
1900 | return raft_get_eid(raft, raft->log_end - 1); | |
1901 | } | |
1902 | ||
1903 | static struct raft_command * | |
1904 | raft_command_create_completed(enum raft_command_status status) | |
1905 | { | |
1906 | ovs_assert(status != RAFT_CMD_INCOMPLETE); | |
1907 | ||
1908 | struct raft_command *cmd = xzalloc(sizeof *cmd); | |
1909 | cmd->n_refs = 1; | |
1910 | cmd->status = status; | |
1911 | return cmd; | |
1912 | } | |
1913 | ||
1914 | static struct raft_command * | |
1915 | raft_command_create_incomplete(struct raft *raft, uint64_t index) | |
1916 | { | |
1917 | struct raft_command *cmd = xzalloc(sizeof *cmd); | |
1918 | cmd->n_refs = 2; /* One for client, one for raft->commands. */ | |
1919 | cmd->index = index; | |
1920 | cmd->status = RAFT_CMD_INCOMPLETE; | |
1921 | hmap_insert(&raft->commands, &cmd->hmap_node, cmd->index); | |
1922 | return cmd; | |
1923 | } | |
1924 | ||
1925 | static struct raft_command * OVS_WARN_UNUSED_RESULT | |
1926 | raft_command_initiate(struct raft *raft, | |
1927 | const struct json *data, const struct json *servers, | |
1928 | const struct uuid *eid) | |
1929 | { | |
1930 | /* Write to local log. */ | |
1931 | uint64_t index = raft->log_end; | |
1932 | if (!raft_handle_write_error( | |
1933 | raft, raft_write_entry( | |
1934 | raft, raft->term, json_nullable_clone(data), eid, | |
1935 | json_nullable_clone(servers)))) { | |
1936 | return raft_command_create_completed(RAFT_CMD_IO_ERROR); | |
1937 | } | |
1938 | ||
1939 | struct raft_command *cmd = raft_command_create_incomplete(raft, index); | |
1940 | if (eid) { | |
1941 | cmd->eid = *eid; | |
1942 | } | |
1943 | ||
1944 | raft_waiter_create(raft, RAFT_W_ENTRY, true)->entry.index = cmd->index; | |
1945 | ||
1946 | /* Write to remote logs. */ | |
1947 | struct raft_server *s; | |
1948 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
1949 | if (!uuid_equals(&s->sid, &raft->sid) && s->next_index == index) { | |
1950 | raft_send_append_request(raft, s, 1, "execute command"); | |
1951 | s->next_index++; | |
1952 | } | |
1953 | } | |
1954 | ||
1955 | return cmd; | |
1956 | } | |
1957 | ||
1958 | static struct raft_command * OVS_WARN_UNUSED_RESULT | |
1959 | raft_command_execute__(struct raft *raft, | |
1960 | const struct json *data, const struct json *servers, | |
1961 | const struct uuid *prereq, struct uuid *result) | |
1962 | { | |
1963 | if (raft->joining || raft->leaving || raft->left || raft->failed) { | |
1964 | return raft_command_create_completed(RAFT_CMD_SHUTDOWN); | |
1965 | } | |
1966 | ||
1967 | if (raft->role != RAFT_LEADER) { | |
1968 | /* Consider proxying the command to the leader. We can only do that if | |
1969 | * we know the leader and the command does not change the set of | |
1970 | * servers. We do not proxy commands without prerequisites, even | |
1971 | * though we could, because in an OVSDB context a log entry doesn't | |
1972 | * make sense without context. */ | |
1973 | if (servers || !data | |
1974 | || raft->role != RAFT_FOLLOWER || uuid_is_zero(&raft->leader_sid) | |
1975 | || !prereq) { | |
1976 | return raft_command_create_completed(RAFT_CMD_NOT_LEADER); | |
1977 | } | |
1978 | } | |
1979 | ||
1980 | struct uuid eid = data ? uuid_random() : UUID_ZERO; | |
1981 | if (result) { | |
1982 | *result = eid; | |
1983 | } | |
1984 | ||
1985 | if (raft->role != RAFT_LEADER) { | |
1986 | const union raft_rpc rpc = { | |
1987 | .execute_command_request = { | |
1988 | .common = { | |
1989 | .type = RAFT_RPC_EXECUTE_COMMAND_REQUEST, | |
1990 | .sid = raft->leader_sid, | |
1991 | }, | |
1992 | .data = CONST_CAST(struct json *, data), | |
1993 | .prereq = *prereq, | |
1994 | .result = eid, | |
1995 | } | |
1996 | }; | |
1997 | if (!raft_send(raft, &rpc)) { | |
1998 | /* Couldn't send command, so it definitely failed. */ | |
1999 | return raft_command_create_completed(RAFT_CMD_NOT_LEADER); | |
2000 | } | |
2001 | ||
2002 | struct raft_command *cmd = raft_command_create_incomplete(raft, 0); | |
2003 | cmd->timestamp = time_msec(); | |
2004 | cmd->eid = eid; | |
2005 | return cmd; | |
2006 | } | |
2007 | ||
2008 | const struct uuid *current_eid = raft_current_eid(raft); | |
2009 | if (prereq && !uuid_equals(prereq, current_eid)) { | |
2010 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
2011 | VLOG_INFO_RL(&rl, "current entry eid "UUID_FMT" does not match " | |
2012 | "prerequisite "UUID_FMT, | |
2013 | UUID_ARGS(current_eid), UUID_ARGS(prereq)); | |
2014 | return raft_command_create_completed(RAFT_CMD_BAD_PREREQ); | |
2015 | } | |
2016 | ||
2017 | return raft_command_initiate(raft, data, servers, &eid); | |
2018 | } | |
2019 | ||
2020 | /* Initiates appending a log entry to 'raft'. The log entry consists of 'data' | |
2021 | * and, if 'prereq' is nonnull, it is only added to the log if the previous | |
2022 | * entry in the log has entry ID 'prereq'. If 'result' is nonnull, it is | |
2023 | * populated with the entry ID for the new log entry. | |
2024 | * | |
2025 | * Returns a "struct raft_command" that may be used to track progress adding | |
2026 | * the log entry. The caller must eventually free the returned structure, with | |
2027 | * raft_command_unref(). */ | |
2028 | struct raft_command * OVS_WARN_UNUSED_RESULT | |
2029 | raft_command_execute(struct raft *raft, const struct json *data, | |
2030 | const struct uuid *prereq, struct uuid *result) | |
2031 | { | |
2032 | return raft_command_execute__(raft, data, NULL, prereq, result); | |
2033 | } | |
2034 | ||
2035 | /* Returns the status of 'cmd'. */ | |
2036 | enum raft_command_status | |
2037 | raft_command_get_status(const struct raft_command *cmd) | |
2038 | { | |
2039 | ovs_assert(cmd->n_refs > 0); | |
2040 | return cmd->status; | |
2041 | } | |
2042 | ||
2043 | /* Returns the index of the log entry at which 'cmd' was committed. | |
2044 | * | |
2045 | * This function works only with successful commands. */ | |
2046 | uint64_t | |
2047 | raft_command_get_commit_index(const struct raft_command *cmd) | |
2048 | { | |
2049 | ovs_assert(cmd->n_refs > 0); | |
2050 | ovs_assert(cmd->status == RAFT_CMD_SUCCESS); | |
2051 | return cmd->index; | |
2052 | } | |
2053 | ||
2054 | /* Frees 'cmd'. */ | |
2055 | void | |
2056 | raft_command_unref(struct raft_command *cmd) | |
2057 | { | |
2058 | if (cmd) { | |
2059 | ovs_assert(cmd->n_refs > 0); | |
2060 | if (!--cmd->n_refs) { | |
2061 | free(cmd); | |
2062 | } | |
2063 | } | |
2064 | } | |
2065 | ||
2066 | /* Causes poll_block() to wake up when 'cmd' has status to report. */ | |
2067 | void | |
2068 | raft_command_wait(const struct raft_command *cmd) | |
2069 | { | |
2070 | if (cmd->status != RAFT_CMD_INCOMPLETE) { | |
2071 | poll_immediate_wake(); | |
2072 | } | |
2073 | } | |
2074 | ||
2075 | static void | |
2076 | raft_command_complete(struct raft *raft, | |
2077 | struct raft_command *cmd, | |
2078 | enum raft_command_status status) | |
2079 | { | |
2080 | if (!uuid_is_zero(&cmd->sid)) { | |
2081 | uint64_t commit_index = status == RAFT_CMD_SUCCESS ? cmd->index : 0; | |
2082 | raft_send_execute_command_reply(raft, &cmd->sid, &cmd->eid, status, | |
2083 | commit_index); | |
2084 | } | |
2085 | ||
2086 | ovs_assert(cmd->status == RAFT_CMD_INCOMPLETE); | |
2087 | ovs_assert(cmd->n_refs > 0); | |
2088 | hmap_remove(&raft->commands, &cmd->hmap_node); | |
2089 | cmd->status = status; | |
2090 | raft_command_unref(cmd); | |
2091 | } | |
2092 | ||
2093 | static void | |
2094 | raft_complete_all_commands(struct raft *raft, enum raft_command_status status) | |
2095 | { | |
2096 | struct raft_command *cmd, *next; | |
2097 | HMAP_FOR_EACH_SAFE (cmd, next, hmap_node, &raft->commands) { | |
2098 | raft_command_complete(raft, cmd, status); | |
2099 | } | |
2100 | } | |
2101 | ||
2102 | static struct raft_command * | |
2103 | raft_find_command_by_index(struct raft *raft, uint64_t index) | |
2104 | { | |
2105 | struct raft_command *cmd; | |
2106 | ||
2107 | HMAP_FOR_EACH_IN_BUCKET (cmd, hmap_node, index, &raft->commands) { | |
2108 | if (cmd->index == index) { | |
2109 | return cmd; | |
2110 | } | |
2111 | } | |
2112 | return NULL; | |
2113 | } | |
2114 | ||
2115 | static struct raft_command * | |
2116 | raft_find_command_by_eid(struct raft *raft, const struct uuid *eid) | |
2117 | { | |
2118 | struct raft_command *cmd; | |
2119 | ||
2120 | HMAP_FOR_EACH (cmd, hmap_node, &raft->commands) { | |
2121 | if (uuid_equals(&cmd->eid, eid)) { | |
2122 | return cmd; | |
2123 | } | |
2124 | } | |
2125 | return NULL; | |
2126 | } | |
2127 | \f | |
2128 | #define RAFT_RPC(ENUM, NAME) \ | |
2129 | static void raft_handle_##NAME(struct raft *, const struct raft_##NAME *); | |
2130 | RAFT_RPC_TYPES | |
2131 | #undef RAFT_RPC | |
2132 | ||
2133 | static void | |
2134 | raft_handle_hello_request(struct raft *raft OVS_UNUSED, | |
2135 | const struct raft_hello_request *hello OVS_UNUSED) | |
2136 | { | |
2137 | } | |
2138 | ||
2139 | /* 'sid' is the server being added. */ | |
2140 | static void | |
2141 | raft_send_add_server_reply__(struct raft *raft, const struct uuid *sid, | |
2142 | const char *address, | |
2143 | bool success, const char *comment) | |
2144 | { | |
2145 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(10, 10); | |
2146 | if (!VLOG_DROP_INFO(&rl)) { | |
2147 | struct ds s = DS_EMPTY_INITIALIZER; | |
2148 | char buf[SID_LEN + 1]; | |
2149 | ds_put_format(&s, "adding %s ("SID_FMT" at %s) " | |
2150 | "to cluster "CID_FMT" %s", | |
2151 | raft_get_nickname(raft, sid, buf, sizeof buf), | |
2152 | SID_ARGS(sid), address, CID_ARGS(&raft->cid), | |
2153 | success ? "succeeded" : "failed"); | |
2154 | if (comment) { | |
2155 | ds_put_format(&s, " (%s)", comment); | |
2156 | } | |
2157 | VLOG_INFO("%s", ds_cstr(&s)); | |
2158 | ds_destroy(&s); | |
2159 | } | |
2160 | ||
2161 | union raft_rpc rpy = { | |
2162 | .add_server_reply = { | |
2163 | .common = { | |
2164 | .type = RAFT_RPC_ADD_SERVER_REPLY, | |
2165 | .sid = *sid, | |
2166 | .comment = CONST_CAST(char *, comment), | |
2167 | }, | |
2168 | .success = success, | |
2169 | } | |
2170 | }; | |
2171 | ||
2172 | struct sset *remote_addresses = &rpy.add_server_reply.remote_addresses; | |
2173 | sset_init(remote_addresses); | |
2174 | if (!raft->joining) { | |
2175 | struct raft_server *s; | |
2176 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
2177 | if (!uuid_equals(&s->sid, &raft->sid)) { | |
2178 | sset_add(remote_addresses, s->address); | |
2179 | } | |
2180 | } | |
2181 | } | |
2182 | ||
2183 | raft_send(raft, &rpy); | |
2184 | ||
2185 | sset_destroy(remote_addresses); | |
2186 | } | |
2187 | ||
2188 | static void | |
2189 | raft_send_remove_server_reply_rpc(struct raft *raft, const struct uuid *sid, | |
2190 | bool success, const char *comment) | |
2191 | { | |
2192 | const union raft_rpc rpy = { | |
2193 | .remove_server_reply = { | |
2194 | .common = { | |
2195 | .type = RAFT_RPC_REMOVE_SERVER_REPLY, | |
2196 | .sid = *sid, | |
2197 | .comment = CONST_CAST(char *, comment), | |
2198 | }, | |
2199 | .success = success, | |
2200 | } | |
2201 | }; | |
2202 | raft_send(raft, &rpy); | |
2203 | } | |
2204 | ||
2205 | static void | |
2206 | raft_send_remove_server_reply__(struct raft *raft, | |
2207 | const struct uuid *target_sid, | |
2208 | const struct uuid *requester_sid, | |
2209 | struct unixctl_conn *requester_conn, | |
2210 | bool success, const char *comment) | |
2211 | { | |
2212 | struct ds s = DS_EMPTY_INITIALIZER; | |
2213 | ds_put_format(&s, "request "); | |
2214 | if (!uuid_is_zero(requester_sid)) { | |
2215 | char buf[SID_LEN + 1]; | |
2216 | ds_put_format(&s, "by %s", | |
2217 | raft_get_nickname(raft, requester_sid, buf, sizeof buf)); | |
2218 | } else { | |
2219 | ds_put_cstr(&s, "via unixctl"); | |
2220 | } | |
2221 | ds_put_cstr(&s, " to remove "); | |
2222 | if (!requester_conn && uuid_equals(target_sid, requester_sid)) { | |
2223 | ds_put_cstr(&s, "itself"); | |
2224 | } else { | |
2225 | char buf[SID_LEN + 1]; | |
2226 | ds_put_cstr(&s, raft_get_nickname(raft, target_sid, buf, sizeof buf)); | |
2227 | } | |
2228 | ds_put_format(&s, " from cluster "CID_FMT" %s", | |
2229 | CID_ARGS(&raft->cid), | |
2230 | success ? "succeeded" : "failed"); | |
2231 | if (comment) { | |
2232 | ds_put_format(&s, " (%s)", comment); | |
2233 | } | |
2234 | ||
2235 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(10, 10); | |
2236 | VLOG_INFO_RL(&rl, "%s", ds_cstr(&s)); | |
2237 | ||
2238 | /* Send RemoveServerReply to the requester (which could be a server or a | |
2239 | * unixctl connection. Also always send it to the removed server; this | |
2240 | * allows it to be sure that it's really removed and update its log and | |
2241 | * disconnect permanently. */ | |
2242 | if (!uuid_is_zero(requester_sid)) { | |
2243 | raft_send_remove_server_reply_rpc(raft, requester_sid, | |
2244 | success, comment); | |
2245 | } | |
2246 | if (!uuid_equals(requester_sid, target_sid)) { | |
2247 | raft_send_remove_server_reply_rpc(raft, target_sid, success, comment); | |
2248 | } | |
2249 | if (requester_conn) { | |
2250 | if (success) { | |
2251 | unixctl_command_reply(requester_conn, ds_cstr(&s)); | |
2252 | } else { | |
2253 | unixctl_command_reply_error(requester_conn, ds_cstr(&s)); | |
2254 | } | |
2255 | } | |
2256 | ||
2257 | ds_destroy(&s); | |
2258 | } | |
2259 | ||
2260 | static void | |
2261 | raft_send_add_server_reply(struct raft *raft, | |
2262 | const struct raft_add_server_request *rq, | |
2263 | bool success, const char *comment) | |
2264 | { | |
2265 | return raft_send_add_server_reply__(raft, &rq->common.sid, rq->address, | |
2266 | success, comment); | |
2267 | } | |
2268 | ||
2269 | static void | |
2270 | raft_send_remove_server_reply(struct raft *raft, | |
2271 | const struct raft_remove_server_request *rq, | |
2272 | bool success, const char *comment) | |
2273 | { | |
2274 | return raft_send_remove_server_reply__(raft, &rq->sid, &rq->common.sid, | |
2275 | rq->requester_conn, success, | |
2276 | comment); | |
2277 | } | |
2278 | ||
2279 | static void | |
2280 | raft_become_follower(struct raft *raft) | |
2281 | { | |
2282 | raft->leader_sid = UUID_ZERO; | |
2283 | if (raft->role == RAFT_FOLLOWER) { | |
2284 | return; | |
2285 | } | |
2286 | ||
2287 | raft->role = RAFT_FOLLOWER; | |
2288 | raft_reset_timer(raft); | |
2289 | ||
2290 | /* Notify clients about lost leadership. | |
2291 | * | |
2292 | * We do not reverse our changes to 'raft->servers' because the new | |
2293 | * configuration is already part of the log. Possibly the configuration | |
2294 | * log entry will not be committed, but until we know that we must use the | |
2295 | * new configuration. Our AppendEntries processing will properly update | |
2296 | * the server configuration later, if necessary. */ | |
2297 | struct raft_server *s; | |
2298 | HMAP_FOR_EACH (s, hmap_node, &raft->add_servers) { | |
2299 | raft_send_add_server_reply__(raft, &s->sid, s->address, false, | |
2300 | RAFT_SERVER_LOST_LEADERSHIP); | |
2301 | } | |
2302 | if (raft->remove_server) { | |
2303 | raft_send_remove_server_reply__(raft, &raft->remove_server->sid, | |
2304 | &raft->remove_server->requester_sid, | |
2305 | raft->remove_server->requester_conn, | |
2306 | false, RAFT_SERVER_LOST_LEADERSHIP); | |
2307 | raft_server_destroy(raft->remove_server); | |
2308 | raft->remove_server = NULL; | |
2309 | } | |
2310 | ||
2311 | raft_complete_all_commands(raft, RAFT_CMD_LOST_LEADERSHIP); | |
2312 | } | |
2313 | ||
2314 | static void | |
2315 | raft_send_append_request(struct raft *raft, | |
2316 | struct raft_server *peer, unsigned int n, | |
2317 | const char *comment) | |
2318 | { | |
2319 | ovs_assert(raft->role == RAFT_LEADER); | |
2320 | ||
2321 | const union raft_rpc rq = { | |
2322 | .append_request = { | |
2323 | .common = { | |
2324 | .type = RAFT_RPC_APPEND_REQUEST, | |
2325 | .sid = peer->sid, | |
2326 | .comment = CONST_CAST(char *, comment), | |
2327 | }, | |
2328 | .term = raft->term, | |
2329 | .prev_log_index = peer->next_index - 1, | |
2330 | .prev_log_term = (peer->next_index - 1 >= raft->log_start | |
2331 | ? raft->entries[peer->next_index - 1 | |
2332 | - raft->log_start].term | |
2333 | : raft->snap.term), | |
2334 | .leader_commit = raft->commit_index, | |
2335 | .entries = &raft->entries[peer->next_index - raft->log_start], | |
2336 | .n_entries = n, | |
2337 | }, | |
2338 | }; | |
2339 | raft_send(raft, &rq); | |
2340 | } | |
2341 | ||
2342 | static void | |
2343 | raft_send_heartbeats(struct raft *raft) | |
2344 | { | |
2345 | struct raft_server *s; | |
2346 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
2347 | if (!uuid_equals(&raft->sid, &s->sid)) { | |
2348 | raft_send_append_request(raft, s, 0, "heartbeat"); | |
2349 | } | |
2350 | } | |
2351 | ||
2352 | /* Send anyone waiting for a command to complete a ping to let them | |
2353 | * know we're still working on it. */ | |
2354 | struct raft_command *cmd; | |
2355 | HMAP_FOR_EACH (cmd, hmap_node, &raft->commands) { | |
2356 | if (!uuid_is_zero(&cmd->sid)) { | |
2357 | raft_send_execute_command_reply(raft, &cmd->sid, | |
2358 | &cmd->eid, | |
2359 | RAFT_CMD_INCOMPLETE, 0); | |
2360 | } | |
2361 | } | |
2362 | } | |
2363 | ||
2364 | /* Initializes the fields in 's' that represent the leader's view of the | |
2365 | * server. */ | |
2366 | static void | |
2367 | raft_server_init_leader(struct raft *raft, struct raft_server *s) | |
2368 | { | |
2369 | s->next_index = raft->log_end; | |
2370 | s->match_index = 0; | |
2371 | s->phase = RAFT_PHASE_STABLE; | |
2372 | } | |
2373 | ||
2374 | static void | |
2375 | raft_become_leader(struct raft *raft) | |
2376 | { | |
2377 | raft_complete_all_commands(raft, RAFT_CMD_LOST_LEADERSHIP); | |
2378 | ||
2379 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5); | |
2380 | VLOG_INFO_RL(&rl, "term %"PRIu64": elected leader by %d+ of " | |
2381 | "%"PRIuSIZE" servers", raft->term, | |
2382 | raft->n_votes, hmap_count(&raft->servers)); | |
2383 | ||
2384 | ovs_assert(raft->role != RAFT_LEADER); | |
2385 | raft->role = RAFT_LEADER; | |
2386 | raft->leader_sid = raft->sid; | |
2387 | raft->election_timeout = LLONG_MAX; | |
2388 | raft->ping_timeout = time_msec() + PING_TIME_MSEC; | |
2389 | ||
2390 | struct raft_server *s; | |
2391 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
2392 | raft_server_init_leader(raft, s); | |
2393 | } | |
2394 | ||
2395 | raft_update_our_match_index(raft, raft->log_end - 1); | |
2396 | raft_send_heartbeats(raft); | |
2397 | ||
2398 | /* Write the fact that we are leader to the log. This is not used by the | |
2399 | * algorithm (although it could be, for quick restart), but it is used for | |
2400 | * offline analysis to check for conformance with the properties that Raft | |
2401 | * guarantees. */ | |
2402 | struct raft_record r = { | |
2403 | .type = RAFT_REC_LEADER, | |
2404 | .term = raft->term, | |
2405 | .sid = raft->sid, | |
2406 | }; | |
2407 | ignore(ovsdb_log_write_and_free(raft->log, raft_record_to_json(&r))); | |
2408 | ||
2409 | /* Initiate a no-op commit. Otherwise we might never find out what's in | |
2410 | * the log. See section 6.4 item 1: | |
2411 | * | |
2412 | * The Leader Completeness Property guarantees that a leader has all | |
2413 | * committed entries, but at the start of its term, it may not know | |
2414 | * which those are. To find out, it needs to commit an entry from its | |
2415 | * term. Raft handles this by having each leader commit a blank no-op | |
2416 | * entry into the log at the start of its term. As soon as this no-op | |
2417 | * entry is committed, the leader’s commit index will be at least as | |
2418 | * large as any other servers’ during its term. | |
2419 | */ | |
2420 | raft_command_unref(raft_command_execute__(raft, NULL, NULL, NULL, NULL)); | |
2421 | } | |
2422 | ||
2423 | /* Processes term 'term' received as part of RPC 'common'. Returns true if the | |
2424 | * caller should continue processing the RPC, false if the caller should reject | |
2425 | * it due to a stale term. */ | |
2426 | static bool | |
2427 | raft_receive_term__(struct raft *raft, const struct raft_rpc_common *common, | |
2428 | uint64_t term) | |
2429 | { | |
2430 | /* Section 3.3 says: | |
2431 | * | |
2432 | * Current terms are exchanged whenever servers communicate; if one | |
2433 | * server’s current term is smaller than the other’s, then it updates | |
2434 | * its current term to the larger value. If a candidate or leader | |
2435 | * discovers that its term is out of date, it immediately reverts to | |
2436 | * follower state. If a server receives a request with a stale term | |
2437 | * number, it rejects the request. | |
2438 | */ | |
2439 | if (term > raft->term) { | |
2440 | if (!raft_set_term(raft, term, NULL)) { | |
2441 | /* Failed to update the term to 'term'. */ | |
2442 | return false; | |
2443 | } | |
2444 | raft_become_follower(raft); | |
2445 | } else if (term < raft->term) { | |
2446 | char buf[SID_LEN + 1]; | |
2447 | VLOG_INFO("rejecting term %"PRIu64" < current term %"PRIu64" received " | |
2448 | "in %s message from server %s", | |
2449 | term, raft->term, | |
2450 | raft_rpc_type_to_string(common->type), | |
2451 | raft_get_nickname(raft, &common->sid, buf, sizeof buf)); | |
2452 | return false; | |
2453 | } | |
2454 | return true; | |
2455 | } | |
2456 | ||
2457 | static void | |
2458 | raft_get_servers_from_log(struct raft *raft, enum vlog_level level) | |
2459 | { | |
2460 | const struct json *servers_json = raft->snap.servers; | |
2461 | for (uint64_t index = raft->log_end - 1; index >= raft->log_start; | |
2462 | index--) { | |
2463 | struct raft_entry *e = &raft->entries[index - raft->log_start]; | |
2464 | if (e->servers) { | |
2465 | servers_json = e->servers; | |
2466 | break; | |
2467 | } | |
2468 | } | |
2469 | ||
2470 | struct hmap servers; | |
2471 | struct ovsdb_error *error = raft_servers_from_json(servers_json, &servers); | |
2472 | ovs_assert(!error); | |
2473 | raft_set_servers(raft, &servers, level); | |
2474 | raft_servers_destroy(&servers); | |
2475 | } | |
2476 | ||
2477 | /* Truncates the log, so that raft->log_end becomes 'new_end'. | |
2478 | * | |
2479 | * Doesn't write anything to disk. In theory, we could truncate the on-disk | |
2480 | * log file, but we don't have the right information to know how long it should | |
2481 | * be. What we actually do is to append entries for older indexes to the | |
2482 | * on-disk log; when we re-read it later, these entries truncate the log. | |
2483 | * | |
2484 | * Returns true if any of the removed log entries were server configuration | |
2485 | * entries, false otherwise. */ | |
2486 | static bool | |
2487 | raft_truncate(struct raft *raft, uint64_t new_end) | |
2488 | { | |
2489 | ovs_assert(new_end >= raft->log_start); | |
2490 | if (raft->log_end > new_end) { | |
2491 | char buf[SID_LEN + 1]; | |
2492 | VLOG_INFO("%s truncating %"PRIu64 " entries from end of log", | |
2493 | raft_get_nickname(raft, &raft->sid, buf, sizeof buf), | |
2494 | raft->log_end - new_end); | |
2495 | } | |
2496 | ||
2497 | bool servers_changed = false; | |
2498 | while (raft->log_end > new_end) { | |
2499 | struct raft_entry *entry = &raft->entries[--raft->log_end | |
2500 | - raft->log_start]; | |
2501 | if (entry->servers) { | |
2502 | servers_changed = true; | |
2503 | } | |
2504 | raft_entry_uninit(entry); | |
2505 | } | |
2506 | return servers_changed; | |
2507 | } | |
2508 | ||
2509 | static const struct json * | |
2510 | raft_peek_next_entry(struct raft *raft, struct uuid *eid) | |
2511 | { | |
2512 | /* Invariant: log_start - 2 <= last_applied <= commit_index < log_end. */ | |
2513 | ovs_assert(raft->log_start <= raft->last_applied + 2); | |
2514 | ovs_assert(raft->last_applied <= raft->commit_index); | |
2515 | ovs_assert(raft->commit_index < raft->log_end); | |
2516 | ||
2517 | if (raft->joining || raft->failed) { | |
2518 | return NULL; | |
2519 | } | |
2520 | ||
2521 | if (raft->log_start == raft->last_applied + 2) { | |
2522 | *eid = raft->snap.eid; | |
2523 | return raft->snap.data; | |
2524 | } | |
2525 | ||
2526 | while (raft->last_applied < raft->commit_index) { | |
2527 | const struct raft_entry *e = raft_get_entry(raft, | |
2528 | raft->last_applied + 1); | |
2529 | if (e->data) { | |
2530 | *eid = e->eid; | |
2531 | return e->data; | |
2532 | } | |
2533 | raft->last_applied++; | |
2534 | } | |
2535 | return NULL; | |
2536 | } | |
2537 | ||
2538 | static const struct json * | |
2539 | raft_get_next_entry(struct raft *raft, struct uuid *eid) | |
2540 | { | |
2541 | const struct json *data = raft_peek_next_entry(raft, eid); | |
2542 | if (data) { | |
2543 | raft->last_applied++; | |
2544 | } | |
2545 | return data; | |
2546 | } | |
2547 | ||
2548 | static void | |
2549 | raft_update_commit_index(struct raft *raft, uint64_t new_commit_index) | |
2550 | { | |
2551 | if (new_commit_index <= raft->commit_index) { | |
2552 | return; | |
2553 | } | |
2554 | ||
2555 | if (raft->role == RAFT_LEADER) { | |
2556 | while (raft->commit_index < new_commit_index) { | |
2557 | uint64_t index = ++raft->commit_index; | |
2558 | const struct raft_entry *e = raft_get_entry(raft, index); | |
2559 | if (e->servers) { | |
2560 | raft_run_reconfigure(raft); | |
2561 | } | |
2562 | if (e->data) { | |
2563 | struct raft_command *cmd | |
2564 | = raft_find_command_by_index(raft, index); | |
2565 | if (cmd) { | |
2566 | raft_command_complete(raft, cmd, RAFT_CMD_SUCCESS); | |
2567 | } | |
2568 | } | |
2569 | } | |
2570 | } else { | |
2571 | raft->commit_index = new_commit_index; | |
2572 | } | |
2573 | ||
2574 | /* Write the commit index to the log. The next time we restart, this | |
2575 | * allows us to start exporting a reasonably fresh log, instead of a log | |
2576 | * that only contains the snapshot. */ | |
2577 | struct raft_record r = { | |
2578 | .type = RAFT_REC_COMMIT_INDEX, | |
2579 | .commit_index = raft->commit_index, | |
2580 | }; | |
2581 | ignore(ovsdb_log_write_and_free(raft->log, raft_record_to_json(&r))); | |
2582 | } | |
2583 | ||
2584 | /* This doesn't use rq->entries (but it does use rq->n_entries). */ | |
2585 | static void | |
2586 | raft_send_append_reply(struct raft *raft, const struct raft_append_request *rq, | |
2587 | enum raft_append_result result, const char *comment) | |
2588 | { | |
2589 | /* Figure 3.1: "If leaderCommit > commitIndex, set commitIndex = | |
2590 | * min(leaderCommit, index of last new entry)" */ | |
2591 | if (result == RAFT_APPEND_OK && rq->leader_commit > raft->commit_index) { | |
2592 | raft_update_commit_index( | |
2593 | raft, MIN(rq->leader_commit, rq->prev_log_index + rq->n_entries)); | |
2594 | } | |
2595 | ||
2596 | /* Send reply. */ | |
2597 | union raft_rpc reply = { | |
2598 | .append_reply = { | |
2599 | .common = { | |
2600 | .type = RAFT_RPC_APPEND_REPLY, | |
2601 | .sid = rq->common.sid, | |
2602 | .comment = CONST_CAST(char *, comment), | |
2603 | }, | |
2604 | .term = raft->term, | |
2605 | .log_end = raft->log_end, | |
2606 | .prev_log_index = rq->prev_log_index, | |
2607 | .prev_log_term = rq->prev_log_term, | |
2608 | .n_entries = rq->n_entries, | |
2609 | .result = result, | |
2610 | } | |
2611 | }; | |
2612 | raft_send(raft, &reply); | |
2613 | } | |
2614 | ||
2615 | /* If 'prev_log_index' exists in 'raft''s log, in term 'prev_log_term', returns | |
2616 | * NULL. Otherwise, returns an explanation for the mismatch. */ | |
2617 | static const char * | |
2618 | match_index_and_term(const struct raft *raft, | |
2619 | uint64_t prev_log_index, uint64_t prev_log_term) | |
2620 | { | |
2621 | if (prev_log_index < raft->log_start - 1) { | |
2622 | return "mismatch before start of log"; | |
2623 | } else if (prev_log_index == raft->log_start - 1) { | |
2624 | if (prev_log_term != raft->snap.term) { | |
2625 | return "prev_term mismatch"; | |
2626 | } | |
2627 | } else if (prev_log_index < raft->log_end) { | |
2628 | if (raft->entries[prev_log_index - raft->log_start].term | |
2629 | != prev_log_term) { | |
2630 | return "term mismatch"; | |
2631 | } | |
2632 | } else { | |
2633 | /* prev_log_index >= raft->log_end */ | |
2634 | return "mismatch past end of log"; | |
2635 | } | |
2636 | return NULL; | |
2637 | } | |
2638 | ||
2639 | static void | |
2640 | raft_handle_append_entries(struct raft *raft, | |
2641 | const struct raft_append_request *rq, | |
2642 | uint64_t prev_log_index, uint64_t prev_log_term, | |
2643 | const struct raft_entry *entries, | |
2644 | unsigned int n_entries) | |
2645 | { | |
2646 | /* Section 3.5: "When sending an AppendEntries RPC, the leader includes | |
2647 | * the index and term of the entry in its log that immediately precedes | |
2648 | * the new entries. If the follower does not find an entry in its log | |
2649 | * with the same index and term, then it refuses the new entries." */ | |
2650 | const char *mismatch = match_index_and_term(raft, prev_log_index, | |
2651 | prev_log_term); | |
2652 | if (mismatch) { | |
2653 | VLOG_INFO("rejecting append_request because previous entry " | |
2654 | "%"PRIu64",%"PRIu64" not in local log (%s)", | |
2655 | prev_log_term, prev_log_index, mismatch); | |
2656 | raft_send_append_reply(raft, rq, RAFT_APPEND_INCONSISTENCY, mismatch); | |
2657 | return; | |
2658 | } | |
2659 | ||
2660 | /* Figure 3.1: "If an existing entry conflicts with a new one (same | |
2661 | * index but different terms), delete the existing entry and all that | |
2662 | * follow it." */ | |
2663 | unsigned int i; | |
2664 | bool servers_changed = false; | |
2665 | for (i = 0; ; i++) { | |
2666 | if (i >= n_entries) { | |
2667 | /* No change. */ | |
2668 | if (rq->common.comment | |
2669 | && !strcmp(rq->common.comment, "heartbeat")) { | |
2670 | raft_send_append_reply(raft, rq, RAFT_APPEND_OK, "heartbeat"); | |
2671 | } else { | |
2672 | raft_send_append_reply(raft, rq, RAFT_APPEND_OK, "no change"); | |
2673 | } | |
2674 | return; | |
2675 | } | |
2676 | ||
2677 | uint64_t log_index = (prev_log_index + 1) + i; | |
2678 | if (log_index >= raft->log_end) { | |
2679 | break; | |
2680 | } | |
2681 | if (raft->entries[log_index - raft->log_start].term | |
2682 | != entries[i].term) { | |
2683 | if (raft_truncate(raft, log_index)) { | |
2684 | servers_changed = true; | |
2685 | } | |
2686 | break; | |
2687 | } | |
2688 | } | |
2689 | ||
2690 | /* Figure 3.1: "Append any entries not already in the log." */ | |
2691 | struct ovsdb_error *error = NULL; | |
2692 | bool any_written = false; | |
2693 | for (; i < n_entries; i++) { | |
2694 | const struct raft_entry *e = &entries[i]; | |
2695 | error = raft_write_entry(raft, e->term, | |
2696 | json_nullable_clone(e->data), &e->eid, | |
2697 | json_nullable_clone(e->servers)); | |
2698 | if (error) { | |
2699 | break; | |
2700 | } | |
2701 | any_written = true; | |
2702 | if (e->servers) { | |
2703 | servers_changed = true; | |
2704 | } | |
2705 | } | |
2706 | ||
2707 | if (any_written) { | |
2708 | raft_waiter_create(raft, RAFT_W_ENTRY, true)->entry.index | |
2709 | = raft->log_end - 1; | |
2710 | } | |
2711 | if (servers_changed) { | |
2712 | /* The set of servers might have changed; check. */ | |
2713 | raft_get_servers_from_log(raft, VLL_INFO); | |
2714 | } | |
2715 | ||
2716 | if (error) { | |
2717 | char *s = ovsdb_error_to_string_free(error); | |
2718 | VLOG_ERR("%s", s); | |
2719 | free(s); | |
2720 | raft_send_append_reply(raft, rq, RAFT_APPEND_IO_ERROR, "I/O error"); | |
2721 | return; | |
2722 | } | |
2723 | ||
2724 | raft_send_append_reply(raft, rq, RAFT_APPEND_OK, "log updated"); | |
2725 | } | |
2726 | ||
2727 | static bool | |
2728 | raft_update_leader(struct raft *raft, const struct uuid *sid) | |
2729 | { | |
2730 | if (raft->role == RAFT_LEADER) { | |
2731 | char buf[SID_LEN + 1]; | |
2732 | VLOG_ERR("this server is leader but server %s claims to be", | |
2733 | raft_get_nickname(raft, sid, buf, sizeof buf)); | |
2734 | return false; | |
2735 | } else if (!uuid_equals(sid, &raft->leader_sid)) { | |
2736 | if (!uuid_is_zero(&raft->leader_sid)) { | |
2737 | char buf1[SID_LEN + 1]; | |
2738 | char buf2[SID_LEN + 1]; | |
2739 | VLOG_ERR("leader for term %"PRIu64" changed from %s to %s", | |
2740 | raft->term, | |
2741 | raft_get_nickname(raft, &raft->leader_sid, | |
2742 | buf1, sizeof buf1), | |
2743 | raft_get_nickname(raft, sid, buf2, sizeof buf2)); | |
2744 | } else { | |
2745 | char buf[SID_LEN + 1]; | |
2746 | VLOG_INFO("server %s is leader for term %"PRIu64, | |
2747 | raft_get_nickname(raft, sid, buf, sizeof buf), | |
2748 | raft->term); | |
2749 | } | |
2750 | raft->leader_sid = *sid; | |
2751 | ||
2752 | /* Record the leader to the log. This is not used by the algorithm | |
2753 | * (although it could be, for quick restart), but it is used for | |
2754 | * offline analysis to check for conformance with the properties | |
2755 | * that Raft guarantees. */ | |
2756 | struct raft_record r = { | |
2757 | .type = RAFT_REC_LEADER, | |
2758 | .term = raft->term, | |
2759 | .sid = *sid, | |
2760 | }; | |
2761 | ignore(ovsdb_log_write_and_free(raft->log, raft_record_to_json(&r))); | |
2762 | } | |
2763 | return true; | |
2764 | } | |
2765 | ||
2766 | static void | |
2767 | raft_handle_append_request(struct raft *raft, | |
2768 | const struct raft_append_request *rq) | |
2769 | { | |
2770 | /* We do not check whether the server that sent the request is part of the | |
2771 | * cluster. As section 4.1 says, "A server accepts AppendEntries requests | |
2772 | * from a leader that is not part of the server’s latest configuration. | |
2773 | * Otherwise, a new server could never be added to the cluster (it would | |
2774 | * never accept any log entries preceding the configuration entry that adds | |
2775 | * the server)." */ | |
2776 | if (!raft_update_leader(raft, &rq->common.sid)) { | |
2777 | raft_send_append_reply(raft, rq, RAFT_APPEND_INCONSISTENCY, | |
2778 | "usurped leadership"); | |
2779 | return; | |
2780 | } | |
2781 | raft_reset_timer(raft); | |
2782 | ||
2783 | /* First check for the common case, where the AppendEntries request is | |
2784 | * entirely for indexes covered by 'log_start' ... 'log_end - 1', something | |
2785 | * like this: | |
2786 | * | |
2787 | * rq->prev_log_index | |
2788 | * | first_entry_index | |
2789 | * | | nth_entry_index | |
2790 | * | | | | |
2791 | * v v v | |
2792 | * +---+---+---+---+ | |
2793 | * T | T | T | T | T | | |
2794 | * +---+-------+---+ | |
2795 | * +---+---+---+---+ | |
2796 | * T | T | T | T | T | | |
2797 | * +---+---+---+---+ | |
2798 | * ^ ^ | |
2799 | * | | | |
2800 | * log_start log_end | |
2801 | * */ | |
2802 | uint64_t first_entry_index = rq->prev_log_index + 1; | |
2803 | uint64_t nth_entry_index = rq->prev_log_index + rq->n_entries; | |
2804 | if (OVS_LIKELY(first_entry_index >= raft->log_start)) { | |
2805 | raft_handle_append_entries(raft, rq, | |
2806 | rq->prev_log_index, rq->prev_log_term, | |
2807 | rq->entries, rq->n_entries); | |
2808 | return; | |
2809 | } | |
2810 | ||
2811 | /* Now a series of checks for odd cases, where the AppendEntries request | |
2812 | * extends earlier than the beginning of our log, into the log entries | |
2813 | * discarded by the most recent snapshot. */ | |
2814 | ||
2815 | /* | |
2816 | * Handle the case where the indexes covered by rq->entries[] are entirely | |
2817 | * disjoint with 'log_start - 1' ... 'log_end - 1', as shown below. So, | |
2818 | * everything in the AppendEntries request must already have been | |
2819 | * committed, and we might as well return true. | |
2820 | * | |
2821 | * rq->prev_log_index | |
2822 | * | first_entry_index | |
2823 | * | | nth_entry_index | |
2824 | * | | | | |
2825 | * v v v | |
2826 | * +---+---+---+---+ | |
2827 | * T | T | T | T | T | | |
2828 | * +---+-------+---+ | |
2829 | * +---+---+---+---+ | |
2830 | * T | T | T | T | T | | |
2831 | * +---+---+---+---+ | |
2832 | * ^ ^ | |
2833 | * | | | |
2834 | * log_start log_end | |
2835 | */ | |
2836 | if (nth_entry_index < raft->log_start - 1) { | |
2837 | raft_send_append_reply(raft, rq, RAFT_APPEND_OK, | |
2838 | "append before log start"); | |
2839 | return; | |
2840 | } | |
2841 | ||
2842 | /* | |
2843 | * Handle the case where the last entry in rq->entries[] has the same index | |
2844 | * as 'log_start - 1', so we can compare their terms: | |
2845 | * | |
2846 | * rq->prev_log_index | |
2847 | * | first_entry_index | |
2848 | * | | nth_entry_index | |
2849 | * | | | | |
2850 | * v v v | |
2851 | * +---+---+---+---+ | |
2852 | * T | T | T | T | T | | |
2853 | * +---+-------+---+ | |
2854 | * +---+---+---+---+ | |
2855 | * T | T | T | T | T | | |
2856 | * +---+---+---+---+ | |
2857 | * ^ ^ | |
2858 | * | | | |
2859 | * log_start log_end | |
2860 | * | |
2861 | * There's actually a sub-case where rq->n_entries == 0, in which we | |
2862 | * compare rq->prev_term: | |
2863 | * | |
2864 | * rq->prev_log_index | |
2865 | * | | |
2866 | * | | |
2867 | * | | |
2868 | * v | |
2869 | * T | |
2870 | * | |
2871 | * +---+---+---+---+ | |
2872 | * T | T | T | T | T | | |
2873 | * +---+---+---+---+ | |
2874 | * ^ ^ | |
2875 | * | | | |
2876 | * log_start log_end | |
2877 | */ | |
2878 | if (nth_entry_index == raft->log_start - 1) { | |
2879 | if (rq->n_entries | |
2880 | ? raft->snap.term == rq->entries[rq->n_entries - 1].term | |
2881 | : raft->snap.term == rq->prev_log_term) { | |
2882 | raft_send_append_reply(raft, rq, RAFT_APPEND_OK, "no change"); | |
2883 | } else { | |
2884 | raft_send_append_reply(raft, rq, RAFT_APPEND_INCONSISTENCY, | |
2885 | "term mismatch"); | |
2886 | } | |
2887 | return; | |
2888 | } | |
2889 | ||
2890 | /* | |
2891 | * We now know that the data in rq->entries[] overlaps the data in | |
2892 | * raft->entries[], as shown below, with some positive 'ofs': | |
2893 | * | |
2894 | * rq->prev_log_index | |
2895 | * | first_entry_index | |
2896 | * | | nth_entry_index | |
2897 | * | | | | |
2898 | * v v v | |
2899 | * +---+---+---+---+---+ | |
2900 | * T | T | T | T | T | T | | |
2901 | * +---+-------+---+---+ | |
2902 | * +---+---+---+---+ | |
2903 | * T | T | T | T | T | | |
2904 | * +---+---+---+---+ | |
2905 | * ^ ^ | |
2906 | * | | | |
2907 | * log_start log_end | |
2908 | * | |
2909 | * |<-- ofs -->| | |
2910 | * | |
2911 | * We transform this into the following by trimming the first 'ofs' | |
2912 | * elements off of rq->entries[], ending up with the following. Notice how | |
2913 | * we retain the term but not the data for rq->entries[ofs - 1]: | |
2914 | * | |
2915 | * first_entry_index + ofs - 1 | |
2916 | * | first_entry_index + ofs | |
2917 | * | | nth_entry_index + ofs | |
2918 | * | | | | |
2919 | * v v v | |
2920 | * +---+---+ | |
2921 | * T | T | T | | |
2922 | * +---+---+ | |
2923 | * +---+---+---+---+ | |
2924 | * T | T | T | T | T | | |
2925 | * +---+---+---+---+ | |
2926 | * ^ ^ | |
2927 | * | | | |
2928 | * log_start log_end | |
2929 | */ | |
2930 | uint64_t ofs = raft->log_start - first_entry_index; | |
2931 | raft_handle_append_entries(raft, rq, | |
2932 | raft->log_start - 1, rq->entries[ofs - 1].term, | |
2933 | &rq->entries[ofs], rq->n_entries - ofs); | |
2934 | } | |
2935 | ||
2936 | /* Returns true if 'raft' has another log entry or snapshot to read. */ | |
2937 | bool | |
2938 | raft_has_next_entry(const struct raft *raft_) | |
2939 | { | |
2940 | struct raft *raft = CONST_CAST(struct raft *, raft_); | |
2941 | struct uuid eid; | |
2942 | return raft_peek_next_entry(raft, &eid) != NULL; | |
2943 | } | |
2944 | ||
2945 | /* Returns the next log entry or snapshot from 'raft', or NULL if there are | |
2946 | * none left to read. Stores the entry ID of the log entry in '*eid'. Stores | |
2947 | * true in '*is_snapshot' if the returned data is a snapshot, false if it is a | |
2948 | * log entry. */ | |
2949 | const struct json * | |
2950 | raft_next_entry(struct raft *raft, struct uuid *eid, bool *is_snapshot) | |
2951 | { | |
2952 | const struct json *data = raft_get_next_entry(raft, eid); | |
2953 | *is_snapshot = data == raft->snap.data; | |
2954 | return data; | |
2955 | } | |
2956 | ||
2957 | /* Returns the log index of the last-read snapshot or log entry. */ | |
2958 | uint64_t | |
2959 | raft_get_applied_index(const struct raft *raft) | |
2960 | { | |
2961 | return raft->last_applied; | |
2962 | } | |
2963 | ||
2964 | /* Returns the log index of the last snapshot or log entry that is available to | |
2965 | * be read. */ | |
2966 | uint64_t | |
2967 | raft_get_commit_index(const struct raft *raft) | |
2968 | { | |
2969 | return raft->commit_index; | |
2970 | } | |
2971 | ||
2972 | static struct raft_server * | |
2973 | raft_find_peer(struct raft *raft, const struct uuid *uuid) | |
2974 | { | |
2975 | struct raft_server *s = raft_find_server(raft, uuid); | |
2976 | return s && !uuid_equals(&raft->sid, &s->sid) ? s : NULL; | |
2977 | } | |
2978 | ||
2979 | static struct raft_server * | |
2980 | raft_find_new_server(struct raft *raft, const struct uuid *uuid) | |
2981 | { | |
2982 | return raft_server_find(&raft->add_servers, uuid); | |
2983 | } | |
2984 | ||
2985 | /* Figure 3.1: "If there exists an N such that N > commitIndex, a | |
2986 | * majority of matchIndex[i] >= N, and log[N].term == currentTerm, set | |
2987 | * commitIndex = N (sections 3.5 and 3.6)." */ | |
2988 | static void | |
2989 | raft_consider_updating_commit_index(struct raft *raft) | |
2990 | { | |
2991 | /* This loop cannot just bail out when it comes across a log entry that | |
2992 | * does not match the criteria. For example, Figure 3.7(d2) shows a | |
2993 | * case where the log entry for term 2 cannot be committed directly | |
2994 | * (because it is not for the current term) but it can be committed as | |
2995 | * a side effect of commit the entry for term 4 (the current term). | |
2996 | * XXX Is there a more efficient way to do this? */ | |
2997 | ovs_assert(raft->role == RAFT_LEADER); | |
2998 | ||
2999 | uint64_t new_commit_index = raft->commit_index; | |
3000 | for (uint64_t idx = MAX(raft->commit_index + 1, raft->log_start); | |
3001 | idx < raft->log_end; idx++) { | |
3002 | if (raft->entries[idx - raft->log_start].term == raft->term) { | |
3003 | size_t count = 0; | |
3004 | struct raft_server *s2; | |
3005 | HMAP_FOR_EACH (s2, hmap_node, &raft->servers) { | |
3006 | if (s2->match_index >= idx) { | |
3007 | count++; | |
3008 | } | |
3009 | } | |
3010 | if (count > hmap_count(&raft->servers) / 2) { | |
3011 | VLOG_DBG("index %"PRIu64" committed to %"PRIuSIZE" servers, " | |
3012 | "applying", idx, count); | |
3013 | new_commit_index = idx; | |
3014 | } | |
3015 | } | |
3016 | } | |
3017 | raft_update_commit_index(raft, new_commit_index); | |
3018 | } | |
3019 | ||
3020 | static void | |
3021 | raft_update_match_index(struct raft *raft, struct raft_server *s, | |
3022 | uint64_t min_index) | |
3023 | { | |
3024 | ovs_assert(raft->role == RAFT_LEADER); | |
3025 | if (min_index > s->match_index) { | |
3026 | s->match_index = min_index; | |
3027 | raft_consider_updating_commit_index(raft); | |
3028 | } | |
3029 | } | |
3030 | ||
3031 | static void | |
3032 | raft_update_our_match_index(struct raft *raft, uint64_t min_index) | |
3033 | { | |
3034 | raft_update_match_index(raft, raft_find_server(raft, &raft->sid), | |
3035 | min_index); | |
3036 | } | |
3037 | ||
3038 | static void | |
3039 | raft_send_install_snapshot_request(struct raft *raft, | |
3040 | const struct raft_server *s, | |
3041 | const char *comment) | |
3042 | { | |
3043 | union raft_rpc rpc = { | |
3044 | .install_snapshot_request = { | |
3045 | .common = { | |
3046 | .type = RAFT_RPC_INSTALL_SNAPSHOT_REQUEST, | |
3047 | .sid = s->sid, | |
3048 | .comment = CONST_CAST(char *, comment), | |
3049 | }, | |
3050 | .term = raft->term, | |
3051 | .last_index = raft->log_start - 1, | |
3052 | .last_term = raft->snap.term, | |
3053 | .last_servers = raft->snap.servers, | |
3054 | .last_eid = raft->snap.eid, | |
3055 | .data = raft->snap.data, | |
3056 | } | |
3057 | }; | |
3058 | raft_send(raft, &rpc); | |
3059 | } | |
3060 | ||
3061 | static void | |
3062 | raft_handle_append_reply(struct raft *raft, | |
3063 | const struct raft_append_reply *rpy) | |
3064 | { | |
3065 | if (raft->role != RAFT_LEADER) { | |
3066 | VLOG_INFO("rejected append_reply (not leader)"); | |
3067 | return; | |
3068 | } | |
3069 | ||
3070 | /* Most commonly we'd be getting an AppendEntries reply from a configured | |
3071 | * server (e.g. a peer), but we can also get them from servers in the | |
3072 | * process of being added. */ | |
3073 | struct raft_server *s = raft_find_peer(raft, &rpy->common.sid); | |
3074 | if (!s) { | |
3075 | s = raft_find_new_server(raft, &rpy->common.sid); | |
3076 | if (!s) { | |
3077 | VLOG_INFO("rejected append_reply from unknown server "SID_FMT, | |
3078 | SID_ARGS(&rpy->common.sid)); | |
3079 | return; | |
3080 | } | |
3081 | } | |
3082 | ||
3083 | if (rpy->result == RAFT_APPEND_OK) { | |
3084 | /* Figure 3.1: "If successful, update nextIndex and matchIndex for | |
3085 | * follower (section 3.5)." */ | |
3086 | uint64_t min_index = rpy->prev_log_index + rpy->n_entries + 1; | |
3087 | if (s->next_index < min_index) { | |
3088 | s->next_index = min_index; | |
3089 | } | |
3090 | raft_update_match_index(raft, s, min_index - 1); | |
3091 | } else { | |
3092 | /* Figure 3.1: "If AppendEntries fails because of log inconsistency, | |
3093 | * decrement nextIndex and retry (section 3.5)." | |
3094 | * | |
3095 | * We also implement the optimization suggested in section 4.2.1: | |
3096 | * "Various approaches can make nextIndex converge to its correct value | |
3097 | * more quickly, including those described in Chapter 3. The simplest | |
3098 | * approach to solving this particular problem of adding a new server, | |
3099 | * however, is to have followers return the length of their logs in the | |
3100 | * AppendEntries response; this allows the leader to cap the follower’s | |
3101 | * nextIndex accordingly." */ | |
3102 | s->next_index = (s->next_index > 0 | |
3103 | ? MIN(s->next_index - 1, rpy->log_end) | |
3104 | : 0); | |
3105 | ||
3106 | if (rpy->result == RAFT_APPEND_IO_ERROR) { | |
3107 | /* Append failed but not because of a log inconsistency. Because | |
3108 | * of the I/O error, there's no point in re-sending the append | |
3109 | * immediately. */ | |
3110 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
3111 | VLOG_INFO_RL(&rl, "%s reported I/O error", s->nickname); | |
3112 | return; | |
3113 | } | |
3114 | } | |
3115 | ||
3116 | /* | |
3117 | * Our behavior here must depend on the value of next_index relative to | |
3118 | * log_start and log_end. There are three cases: | |
3119 | * | |
3120 | * Case 1 | Case 2 | Case 3 | |
3121 | * <---------------->|<------------->|<------------------> | |
3122 | * | | | |
3123 | * | |
3124 | * +---+---+---+---+ | |
3125 | * T | T | T | T | T | | |
3126 | * +---+---+---+---+ | |
3127 | * ^ ^ | |
3128 | * | | | |
3129 | * log_start log_end | |
3130 | */ | |
3131 | if (s->next_index < raft->log_start) { | |
3132 | /* Case 1. */ | |
3133 | raft_send_install_snapshot_request(raft, s, NULL); | |
3134 | } else if (s->next_index < raft->log_end) { | |
3135 | /* Case 2. */ | |
3136 | raft_send_append_request(raft, s, 1, NULL); | |
3137 | } else { | |
3138 | /* Case 3. */ | |
3139 | if (s->phase == RAFT_PHASE_CATCHUP) { | |
3140 | s->phase = RAFT_PHASE_CAUGHT_UP; | |
3141 | raft_run_reconfigure(raft); | |
3142 | } | |
3143 | } | |
3144 | } | |
3145 | ||
3146 | static bool | |
3147 | raft_should_suppress_disruptive_server(struct raft *raft, | |
3148 | const union raft_rpc *rpc) | |
3149 | { | |
3150 | if (rpc->type != RAFT_RPC_VOTE_REQUEST) { | |
3151 | return false; | |
3152 | } | |
3153 | ||
3154 | /* Section 4.2.3 "Disruptive Servers" says: | |
3155 | * | |
3156 | * ...if a server receives a RequestVote request within the minimum | |
3157 | * election timeout of hearing from a current leader, it does not update | |
3158 | * its term or grant its vote... | |
3159 | * | |
3160 | * ...This change conflicts with the leadership transfer mechanism as | |
3161 | * described in Chapter 3, in which a server legitimately starts an | |
3162 | * election without waiting an election timeout. In that case, | |
3163 | * RequestVote messages should be processed by other servers even when | |
3164 | * they believe a current cluster leader exists. Those RequestVote | |
3165 | * requests can include a special flag to indicate this behavior (“I | |
3166 | * have permission to disrupt the leader--it told me to!”). | |
3167 | * | |
3168 | * This clearly describes how the followers should act, but not the leader. | |
3169 | * We just ignore vote requests that arrive at a current leader. This | |
3170 | * seems to be fairly safe, since a majority other than the current leader | |
3171 | * can still elect a new leader and the first AppendEntries from that new | |
3172 | * leader will depose the current leader. */ | |
3173 | const struct raft_vote_request *rq = raft_vote_request_cast(rpc); | |
3174 | if (rq->leadership_transfer) { | |
3175 | return false; | |
3176 | } | |
3177 | ||
3178 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
3179 | long long int now = time_msec(); | |
3180 | switch (raft->role) { | |
3181 | case RAFT_LEADER: | |
3182 | VLOG_WARN_RL(&rl, "ignoring vote request received as leader"); | |
3183 | return true; | |
3184 | ||
3185 | case RAFT_FOLLOWER: | |
3186 | if (now < raft->election_base + ELECTION_BASE_MSEC) { | |
3187 | VLOG_WARN_RL(&rl, "ignoring vote request received after only " | |
3188 | "%lld ms (minimum election time is %d ms)", | |
3189 | now - raft->election_base, ELECTION_BASE_MSEC); | |
3190 | return true; | |
3191 | } | |
3192 | return false; | |
3193 | ||
3194 | case RAFT_CANDIDATE: | |
3195 | return false; | |
3196 | ||
3197 | default: | |
3198 | OVS_NOT_REACHED(); | |
3199 | } | |
3200 | } | |
3201 | ||
3202 | /* Returns true if a reply should be sent. */ | |
3203 | static bool | |
3204 | raft_handle_vote_request__(struct raft *raft, | |
3205 | const struct raft_vote_request *rq) | |
3206 | { | |
3207 | /* Figure 3.1: "If votedFor is null or candidateId, and candidate's vote is | |
3208 | * at least as up-to-date as receiver's log, grant vote (sections 3.4, | |
3209 | * 3.6)." */ | |
3210 | if (uuid_equals(&raft->vote, &rq->common.sid)) { | |
3211 | /* Already voted for this candidate in this term. Resend vote. */ | |
3212 | return true; | |
3213 | } else if (!uuid_is_zero(&raft->vote)) { | |
3214 | /* Already voted for different candidate in this term. Send a reply | |
3215 | * saying what candidate we did vote for. This isn't a necessary part | |
3216 | * of the Raft protocol but it can make debugging easier. */ | |
3217 | return true; | |
3218 | } | |
3219 | ||
3220 | /* Section 3.6.1: "The RequestVote RPC implements this restriction: the RPC | |
3221 | * includes information about the candidate’s log, and the voter denies its | |
3222 | * vote if its own log is more up-to-date than that of the candidate. Raft | |
3223 | * determines which of two logs is more up-to-date by comparing the index | |
3224 | * and term of the last entries in the logs. If the logs have last entries | |
3225 | * with different terms, then the log with the later term is more | |
3226 | * up-to-date. If the logs end with the same term, then whichever log is | |
3227 | * longer is more up-to-date." */ | |
3228 | uint64_t last_term = (raft->log_end > raft->log_start | |
3229 | ? raft->entries[raft->log_end - 1 | |
3230 | - raft->log_start].term | |
3231 | : raft->snap.term); | |
3232 | if (last_term > rq->last_log_term | |
3233 | || (last_term == rq->last_log_term | |
3234 | && raft->log_end - 1 > rq->last_log_index)) { | |
3235 | /* Our log is more up-to-date than the peer's. Withhold vote. */ | |
3236 | return false; | |
3237 | } | |
3238 | ||
3239 | /* Record a vote for the peer. */ | |
3240 | if (!raft_set_term(raft, raft->term, &rq->common.sid)) { | |
3241 | return false; | |
3242 | } | |
3243 | ||
3244 | raft_reset_timer(raft); | |
3245 | ||
3246 | return true; | |
3247 | } | |
3248 | ||
3249 | static void | |
3250 | raft_send_vote_reply(struct raft *raft, const struct uuid *dst, | |
3251 | const struct uuid *vote) | |
3252 | { | |
3253 | union raft_rpc rpy = { | |
3254 | .vote_reply = { | |
3255 | .common = { | |
3256 | .type = RAFT_RPC_VOTE_REPLY, | |
3257 | .sid = *dst, | |
3258 | }, | |
3259 | .term = raft->term, | |
3260 | .vote = *vote, | |
3261 | }, | |
3262 | }; | |
3263 | raft_send(raft, &rpy); | |
3264 | } | |
3265 | ||
3266 | static void | |
3267 | raft_handle_vote_request(struct raft *raft, | |
3268 | const struct raft_vote_request *rq) | |
3269 | { | |
3270 | if (raft_handle_vote_request__(raft, rq)) { | |
3271 | raft_send_vote_reply(raft, &rq->common.sid, &raft->vote); | |
3272 | } | |
3273 | } | |
3274 | ||
3275 | static void | |
3276 | raft_handle_vote_reply(struct raft *raft, | |
3277 | const struct raft_vote_reply *rpy) | |
3278 | { | |
3279 | if (!raft_receive_term__(raft, &rpy->common, rpy->term)) { | |
3280 | return; | |
3281 | } | |
3282 | ||
3283 | if (raft->role != RAFT_CANDIDATE) { | |
3284 | return; | |
3285 | } | |
3286 | ||
3287 | struct raft_server *s = raft_find_peer(raft, &rpy->common.sid); | |
3288 | if (s) { | |
3289 | raft_accept_vote(raft, s, &rpy->vote); | |
3290 | } | |
3291 | } | |
3292 | ||
3293 | /* Returns true if 'raft''s log contains reconfiguration entries that have not | |
3294 | * yet been committed. */ | |
3295 | static bool | |
3296 | raft_has_uncommitted_configuration(const struct raft *raft) | |
3297 | { | |
3298 | for (uint64_t i = raft->commit_index + 1; i < raft->log_end; i++) { | |
3299 | ovs_assert(i >= raft->log_start); | |
3300 | const struct raft_entry *e = &raft->entries[i - raft->log_start]; | |
3301 | if (e->servers) { | |
3302 | return true; | |
3303 | } | |
3304 | } | |
3305 | return false; | |
3306 | } | |
3307 | ||
3308 | static void | |
3309 | raft_log_reconfiguration(struct raft *raft) | |
3310 | { | |
3311 | struct json *servers_json = raft_servers_to_json(&raft->servers); | |
3312 | raft_command_unref(raft_command_execute__( | |
3313 | raft, NULL, servers_json, NULL, NULL)); | |
3314 | json_destroy(servers_json); | |
3315 | } | |
3316 | ||
3317 | static void | |
3318 | raft_run_reconfigure(struct raft *raft) | |
3319 | { | |
3320 | ovs_assert(raft->role == RAFT_LEADER); | |
3321 | ||
3322 | /* Reconfiguration only progresses when configuration changes commit. */ | |
3323 | if (raft_has_uncommitted_configuration(raft)) { | |
3324 | return; | |
3325 | } | |
3326 | ||
3327 | /* If we were waiting for a configuration change to commit, it's done. */ | |
3328 | struct raft_server *s; | |
3329 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
3330 | if (s->phase == RAFT_PHASE_COMMITTING) { | |
3331 | raft_send_add_server_reply__(raft, &s->sid, s->address, | |
3332 | true, RAFT_SERVER_COMPLETED); | |
3333 | s->phase = RAFT_PHASE_STABLE; | |
3334 | } | |
3335 | } | |
3336 | if (raft->remove_server) { | |
3337 | raft_send_remove_server_reply__(raft, &raft->remove_server->sid, | |
3338 | &raft->remove_server->requester_sid, | |
3339 | raft->remove_server->requester_conn, | |
3340 | true, RAFT_SERVER_COMPLETED); | |
3341 | raft_server_destroy(raft->remove_server); | |
3342 | raft->remove_server = NULL; | |
3343 | } | |
3344 | ||
3345 | /* If a new server is caught up, add it to the configuration. */ | |
3346 | HMAP_FOR_EACH (s, hmap_node, &raft->add_servers) { | |
3347 | if (s->phase == RAFT_PHASE_CAUGHT_UP) { | |
3348 | /* Move 's' from 'raft->add_servers' to 'raft->servers'. */ | |
3349 | hmap_remove(&raft->add_servers, &s->hmap_node); | |
3350 | hmap_insert(&raft->servers, &s->hmap_node, uuid_hash(&s->sid)); | |
3351 | ||
3352 | /* Mark 's' as waiting for commit. */ | |
3353 | s->phase = RAFT_PHASE_COMMITTING; | |
3354 | ||
3355 | raft_log_reconfiguration(raft); | |
3356 | ||
3357 | /* When commit completes we'll transition to RAFT_PHASE_STABLE and | |
3358 | * send a RAFT_SERVER_OK reply. */ | |
3359 | ||
3360 | return; | |
3361 | } | |
3362 | } | |
3363 | ||
3364 | /* Remove a server, if one is scheduled for removal. */ | |
3365 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
3366 | if (s->phase == RAFT_PHASE_REMOVE) { | |
3367 | hmap_remove(&raft->servers, &s->hmap_node); | |
3368 | raft->remove_server = s; | |
3369 | ||
3370 | raft_log_reconfiguration(raft); | |
3371 | ||
3372 | return; | |
3373 | } | |
3374 | } | |
3375 | } | |
3376 | ||
3377 | static void | |
3378 | raft_handle_add_server_request(struct raft *raft, | |
3379 | const struct raft_add_server_request *rq) | |
3380 | { | |
3381 | /* Figure 4.1: "1. Reply NOT_LEADER if not leader (section 6.2)." */ | |
3382 | if (raft->role != RAFT_LEADER) { | |
3383 | raft_send_add_server_reply(raft, rq, false, RAFT_SERVER_NOT_LEADER); | |
3384 | return; | |
3385 | } | |
3386 | ||
3387 | /* Check for an existing server. */ | |
3388 | struct raft_server *s = raft_find_server(raft, &rq->common.sid); | |
3389 | if (s) { | |
3390 | /* If the server is scheduled to be removed, cancel it. */ | |
3391 | if (s->phase == RAFT_PHASE_REMOVE) { | |
3392 | s->phase = RAFT_PHASE_STABLE; | |
3393 | raft_send_add_server_reply(raft, rq, false, RAFT_SERVER_CANCELED); | |
3394 | return; | |
3395 | } | |
3396 | ||
3397 | /* If the server is being added, then it's in progress. */ | |
3398 | if (s->phase != RAFT_PHASE_STABLE) { | |
3399 | raft_send_add_server_reply(raft, rq, | |
3400 | false, RAFT_SERVER_IN_PROGRESS); | |
3401 | } | |
3402 | ||
3403 | /* Nothing to do--server is already part of the configuration. */ | |
3404 | raft_send_add_server_reply(raft, rq, | |
3405 | true, RAFT_SERVER_ALREADY_PRESENT); | |
3406 | return; | |
3407 | } | |
3408 | ||
3409 | /* Check for a server being removed. */ | |
3410 | if (raft->remove_server | |
3411 | && uuid_equals(&rq->common.sid, &raft->remove_server->sid)) { | |
3412 | raft_send_add_server_reply(raft, rq, false, RAFT_SERVER_COMMITTING); | |
3413 | return; | |
3414 | } | |
3415 | ||
3416 | /* Check for a server already being added. */ | |
3417 | if (raft_find_new_server(raft, &rq->common.sid)) { | |
3418 | raft_send_add_server_reply(raft, rq, false, RAFT_SERVER_IN_PROGRESS); | |
3419 | return; | |
3420 | } | |
3421 | ||
3422 | /* Add server to 'add_servers'. */ | |
3423 | s = raft_server_add(&raft->add_servers, &rq->common.sid, rq->address); | |
3424 | raft_server_init_leader(raft, s); | |
3425 | s->requester_sid = rq->common.sid; | |
3426 | s->requester_conn = NULL; | |
3427 | s->phase = RAFT_PHASE_CATCHUP; | |
3428 | ||
3429 | /* Start sending the log. If this is the first time we've tried to add | |
3430 | * this server, then this will quickly degenerate into an InstallSnapshot | |
3431 | * followed by a series of AddEntries, but if it's a retry of an earlier | |
3432 | * AddRequest that was interrupted (e.g. by a timeout or a loss of | |
3433 | * leadership) then it will gracefully resume populating the log. | |
3434 | * | |
3435 | * See the last few paragraphs of section 4.2.1 for further insight. */ | |
3436 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(10, 10); | |
3437 | VLOG_INFO_RL(&rl, | |
3438 | "starting to add server %s ("SID_FMT" at %s) " | |
3439 | "to cluster "CID_FMT, s->nickname, SID_ARGS(&s->sid), | |
3440 | rq->address, CID_ARGS(&raft->cid)); | |
3441 | raft_send_append_request(raft, s, 0, "initialize new server"); | |
3442 | } | |
3443 | ||
3444 | static void | |
3445 | raft_handle_add_server_reply(struct raft *raft, | |
3446 | const struct raft_add_server_reply *rpy) | |
3447 | { | |
3448 | if (!raft->joining) { | |
3449 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
3450 | VLOG_WARN_RL(&rl, "received add_server_reply even though we're " | |
3451 | "already part of the cluster"); | |
3452 | return; | |
3453 | } | |
3454 | ||
3455 | if (rpy->success) { | |
3456 | raft->joining = false; | |
3457 | ||
3458 | /* It is tempting, at this point, to check that this server is part of | |
3459 | * the current configuration. However, this is not necessarily the | |
3460 | * case, because the log entry that added this server to the cluster | |
3461 | * might have been committed by a majority of the cluster that does not | |
3462 | * include this one. This actually happens in testing. */ | |
3463 | } else { | |
3464 | const char *address; | |
3465 | SSET_FOR_EACH (address, &rpy->remote_addresses) { | |
3466 | if (sset_add(&raft->remote_addresses, address)) { | |
3467 | VLOG_INFO("%s: learned new server address for joining cluster", | |
3468 | address); | |
3469 | } | |
3470 | } | |
3471 | } | |
3472 | } | |
3473 | ||
3474 | /* This is called by raft_unixctl_kick() as well as via RPC. */ | |
3475 | static void | |
3476 | raft_handle_remove_server_request(struct raft *raft, | |
3477 | const struct raft_remove_server_request *rq) | |
3478 | { | |
3479 | /* Figure 4.1: "1. Reply NOT_LEADER if not leader (section 6.2)." */ | |
3480 | if (raft->role != RAFT_LEADER) { | |
3481 | raft_send_remove_server_reply(raft, rq, false, RAFT_SERVER_NOT_LEADER); | |
3482 | return; | |
3483 | } | |
3484 | ||
3485 | /* If the server to remove is currently waiting to be added, cancel it. */ | |
3486 | struct raft_server *target = raft_find_new_server(raft, &rq->sid); | |
3487 | if (target) { | |
3488 | raft_send_add_server_reply__(raft, &target->sid, target->address, | |
3489 | false, RAFT_SERVER_CANCELED); | |
3490 | hmap_remove(&raft->add_servers, &target->hmap_node); | |
3491 | raft_server_destroy(target); | |
3492 | return; | |
3493 | } | |
3494 | ||
3495 | /* If the server isn't configured, report that. */ | |
3496 | target = raft_find_server(raft, &rq->sid); | |
3497 | if (!target) { | |
3498 | raft_send_remove_server_reply(raft, rq, | |
3499 | true, RAFT_SERVER_ALREADY_GONE); | |
3500 | return; | |
3501 | } | |
3502 | ||
3503 | /* Check whether we're waiting for the addition of the server to commit. */ | |
3504 | if (target->phase == RAFT_PHASE_COMMITTING) { | |
3505 | raft_send_remove_server_reply(raft, rq, false, RAFT_SERVER_COMMITTING); | |
3506 | return; | |
3507 | } | |
3508 | ||
3509 | /* Check whether the server is already scheduled for removal. */ | |
3510 | if (target->phase == RAFT_PHASE_REMOVE) { | |
3511 | raft_send_remove_server_reply(raft, rq, | |
3512 | false, RAFT_SERVER_IN_PROGRESS); | |
3513 | return; | |
3514 | } | |
3515 | ||
3516 | /* Make sure that if we remove this server then that at least one other | |
3517 | * server will be left. We don't count servers currently being added (in | |
3518 | * 'add_servers') since those could fail. */ | |
3519 | struct raft_server *s; | |
3520 | int n = 0; | |
3521 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
3522 | if (s != target && s->phase != RAFT_PHASE_REMOVE) { | |
3523 | n++; | |
3524 | } | |
3525 | } | |
3526 | if (!n) { | |
3527 | raft_send_remove_server_reply(raft, rq, false, RAFT_SERVER_EMPTY); | |
3528 | return; | |
3529 | } | |
3530 | ||
3531 | /* Mark the server for removal. */ | |
3532 | target->phase = RAFT_PHASE_REMOVE; | |
3533 | if (rq->requester_conn) { | |
3534 | target->requester_sid = UUID_ZERO; | |
3535 | unixctl_command_reply(rq->requester_conn, "started removal"); | |
3536 | } else { | |
3537 | target->requester_sid = rq->common.sid; | |
3538 | target->requester_conn = NULL; | |
3539 | } | |
3540 | ||
3541 | raft_run_reconfigure(raft); | |
3542 | /* Operation in progress, reply will be sent later. */ | |
3543 | } | |
3544 | ||
3545 | static void | |
3546 | raft_handle_remove_server_reply(struct raft *raft, | |
3547 | const struct raft_remove_server_reply *rpc) | |
3548 | { | |
3549 | if (rpc->success) { | |
3550 | VLOG_INFO(SID_FMT": finished leaving cluster "CID_FMT, | |
3551 | SID_ARGS(&raft->sid), CID_ARGS(&raft->cid)); | |
3552 | ||
3553 | raft_record_note(raft, "left", "this server left the cluster"); | |
3554 | ||
3555 | raft->leaving = false; | |
3556 | raft->left = true; | |
3557 | } | |
3558 | } | |
3559 | ||
3560 | static bool | |
3561 | raft_handle_write_error(struct raft *raft, struct ovsdb_error *error) | |
3562 | { | |
3563 | if (error && !raft->failed) { | |
3564 | raft->failed = true; | |
3565 | ||
3566 | char *s = ovsdb_error_to_string_free(error); | |
3567 | VLOG_WARN("%s: entering failure mode due to I/O error (%s)", | |
3568 | raft->name, s); | |
3569 | free(s); | |
3570 | } | |
3571 | return !raft->failed; | |
3572 | } | |
3573 | ||
3574 | static struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
3575 | raft_write_snapshot(struct raft *raft, struct ovsdb_log *log, | |
3576 | uint64_t new_log_start, | |
3577 | const struct raft_entry *new_snapshot) | |
3578 | { | |
3579 | struct raft_header h = { | |
3580 | .sid = raft->sid, | |
3581 | .cid = raft->cid, | |
3582 | .name = raft->name, | |
3583 | .local_address = raft->local_address, | |
3584 | .snap_index = new_log_start - 1, | |
3585 | .snap = *new_snapshot, | |
3586 | }; | |
3587 | struct ovsdb_error *error = ovsdb_log_write_and_free( | |
3588 | log, raft_header_to_json(&h)); | |
3589 | if (error) { | |
3590 | return error; | |
3591 | } | |
3592 | ovsdb_log_mark_base(raft->log); | |
3593 | ||
3594 | /* Write log records. */ | |
3595 | for (uint64_t index = new_log_start; index < raft->log_end; index++) { | |
3596 | const struct raft_entry *e = &raft->entries[index - raft->log_start]; | |
3597 | struct raft_record r = { | |
3598 | .type = RAFT_REC_ENTRY, | |
3599 | .term = e->term, | |
3600 | .entry = { | |
3601 | .index = index, | |
3602 | .data = e->data, | |
3603 | .servers = e->servers, | |
3604 | .eid = e->eid, | |
3605 | }, | |
3606 | }; | |
3607 | error = ovsdb_log_write_and_free(log, raft_record_to_json(&r)); | |
3608 | if (error) { | |
3609 | return error; | |
3610 | } | |
3611 | } | |
3612 | ||
3613 | /* Write term and vote (if any). | |
3614 | * | |
3615 | * The term is redundant if we wrote a log record for that term above. The | |
3616 | * vote, if any, is never redundant. | |
3617 | */ | |
3618 | error = raft_write_state(log, raft->term, &raft->vote); | |
3619 | if (error) { | |
3620 | return error; | |
3621 | } | |
3622 | ||
3623 | /* Write commit_index if it's beyond the new start of the log. */ | |
3624 | if (raft->commit_index >= new_log_start) { | |
3625 | struct raft_record r = { | |
3626 | .type = RAFT_REC_COMMIT_INDEX, | |
3627 | .commit_index = raft->commit_index, | |
3628 | }; | |
3629 | return ovsdb_log_write_and_free(log, raft_record_to_json(&r)); | |
3630 | } | |
3631 | return NULL; | |
3632 | } | |
3633 | ||
3634 | static struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
3635 | raft_save_snapshot(struct raft *raft, | |
3636 | uint64_t new_start, const struct raft_entry *new_snapshot) | |
3637 | ||
3638 | { | |
3639 | struct ovsdb_log *new_log; | |
3640 | struct ovsdb_error *error; | |
3641 | error = ovsdb_log_replace_start(raft->log, &new_log); | |
3642 | if (error) { | |
3643 | return error; | |
3644 | } | |
3645 | ||
3646 | error = raft_write_snapshot(raft, new_log, new_start, new_snapshot); | |
3647 | if (error) { | |
3648 | ovsdb_log_replace_abort(new_log); | |
3649 | return error; | |
3650 | } | |
3651 | ||
3652 | return ovsdb_log_replace_commit(raft->log, new_log); | |
3653 | } | |
3654 | ||
3655 | static bool | |
3656 | raft_handle_install_snapshot_request__( | |
3657 | struct raft *raft, const struct raft_install_snapshot_request *rq) | |
3658 | { | |
3659 | raft_reset_timer(raft); | |
3660 | ||
3661 | /* | |
3662 | * Our behavior here depend on new_log_start in the snapshot compared to | |
3663 | * log_start and log_end. There are three cases: | |
3664 | * | |
3665 | * Case 1 | Case 2 | Case 3 | |
3666 | * <---------------->|<------------->|<------------------> | |
3667 | * | | | |
3668 | * | |
3669 | * +---+---+---+---+ | |
3670 | * T | T | T | T | T | | |
3671 | * +---+---+---+---+ | |
3672 | * ^ ^ | |
3673 | * | | | |
3674 | * log_start log_end | |
3675 | */ | |
3676 | uint64_t new_log_start = rq->last_index + 1; | |
3677 | if (new_log_start < raft->log_start) { | |
3678 | /* Case 1: The new snapshot covers less than our current one. Nothing | |
3679 | * to do. */ | |
3680 | return true; | |
3681 | } else if (new_log_start < raft->log_end) { | |
3682 | /* Case 2: The new snapshot starts in the middle of our log. We could | |
3683 | * discard the first 'new_log_start - raft->log_start' entries in the | |
3684 | * log. But there's not much value in that, since snapshotting is | |
3685 | * supposed to be a local decision. Just skip it. */ | |
3686 | return true; | |
3687 | } | |
3688 | ||
3689 | /* Case 3: The new snapshot starts past the end of our current log, so | |
3690 | * discard all of our current log. */ | |
3691 | const struct raft_entry new_snapshot = { | |
3692 | .term = rq->last_term, | |
3693 | .data = rq->data, | |
3694 | .eid = rq->last_eid, | |
3695 | .servers = rq->last_servers, | |
3696 | }; | |
3697 | struct ovsdb_error *error = raft_save_snapshot(raft, new_log_start, | |
3698 | &new_snapshot); | |
3699 | if (error) { | |
3700 | char *error_s = ovsdb_error_to_string(error); | |
3701 | VLOG_WARN("could not save snapshot: %s", error_s); | |
3702 | free(error_s); | |
3703 | return false; | |
3704 | } | |
3705 | ||
3706 | for (size_t i = 0; i < raft->log_end - raft->log_start; i++) { | |
3707 | raft_entry_uninit(&raft->entries[i]); | |
3708 | } | |
3709 | raft->log_start = raft->log_end = new_log_start; | |
3710 | raft->log_synced = raft->log_end - 1; | |
3711 | raft->commit_index = raft->log_start - 1; | |
3712 | if (raft->last_applied < raft->commit_index) { | |
3713 | raft->last_applied = raft->log_start - 2; | |
3714 | } | |
3715 | ||
3716 | raft_entry_uninit(&raft->snap); | |
3717 | raft_entry_clone(&raft->snap, &new_snapshot); | |
3718 | ||
3719 | raft_get_servers_from_log(raft, VLL_INFO); | |
3720 | ||
3721 | return true; | |
3722 | } | |
3723 | ||
3724 | static void | |
3725 | raft_handle_install_snapshot_request( | |
3726 | struct raft *raft, const struct raft_install_snapshot_request *rq) | |
3727 | { | |
3728 | if (raft_handle_install_snapshot_request__(raft, rq)) { | |
3729 | union raft_rpc rpy = { | |
3730 | .install_snapshot_reply = { | |
3731 | .common = { | |
3732 | .type = RAFT_RPC_INSTALL_SNAPSHOT_REPLY, | |
3733 | .sid = rq->common.sid, | |
3734 | }, | |
3735 | .term = raft->term, | |
3736 | .last_index = rq->last_index, | |
3737 | .last_term = rq->last_term, | |
3738 | }, | |
3739 | }; | |
3740 | raft_send(raft, &rpy); | |
3741 | } | |
3742 | } | |
3743 | ||
3744 | static void | |
3745 | raft_handle_install_snapshot_reply( | |
3746 | struct raft *raft, const struct raft_install_snapshot_reply *rpy) | |
3747 | { | |
3748 | /* We might get an InstallSnapshot reply from a configured server (e.g. a | |
3749 | * peer) or a server in the process of being added. */ | |
3750 | struct raft_server *s = raft_find_peer(raft, &rpy->common.sid); | |
3751 | if (!s) { | |
3752 | s = raft_find_new_server(raft, &rpy->common.sid); | |
3753 | if (!s) { | |
3754 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
3755 | VLOG_INFO_RL(&rl, "cluster "CID_FMT": received %s from " | |
3756 | "unknown server "SID_FMT, CID_ARGS(&raft->cid), | |
3757 | raft_rpc_type_to_string(rpy->common.type), | |
3758 | SID_ARGS(&rpy->common.sid)); | |
3759 | return; | |
3760 | } | |
3761 | } | |
3762 | ||
3763 | if (rpy->last_index != raft->log_start - 1 || | |
3764 | rpy->last_term != raft->snap.term) { | |
3765 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
3766 | VLOG_INFO_RL(&rl, "cluster "CID_FMT": server %s installed " | |
3767 | "out-of-date snapshot, starting over", | |
3768 | CID_ARGS(&raft->cid), s->nickname); | |
3769 | raft_send_install_snapshot_request(raft, s, | |
3770 | "installed obsolete snapshot"); | |
3771 | return; | |
3772 | } | |
3773 | ||
3774 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(10, 10); | |
3775 | VLOG_INFO_RL(&rl, "cluster "CID_FMT": installed snapshot on server %s " | |
3776 | " up to %"PRIu64":%"PRIu64, CID_ARGS(&raft->cid), | |
3777 | s->nickname, rpy->last_term, rpy->last_index); | |
3778 | s->next_index = raft->log_end; | |
3779 | raft_send_append_request(raft, s, 0, "snapshot installed"); | |
3780 | } | |
3781 | ||
3782 | /* Returns true if 'raft' has grown enough since the last snapshot that | |
3783 | * reducing the log to a snapshot would be valuable, false otherwise. */ | |
3784 | bool | |
3785 | raft_grew_lots(const struct raft *raft) | |
3786 | { | |
3787 | return ovsdb_log_grew_lots(raft->log); | |
3788 | } | |
3789 | ||
3790 | /* Returns the number of log entries that could be trimmed off the on-disk log | |
3791 | * by snapshotting. */ | |
3792 | uint64_t | |
3793 | raft_get_log_length(const struct raft *raft) | |
3794 | { | |
3795 | return (raft->last_applied < raft->log_start | |
3796 | ? 0 | |
3797 | : raft->last_applied - raft->log_start + 1); | |
3798 | } | |
3799 | ||
3800 | /* Returns true if taking a snapshot of 'raft', with raft_store_snapshot(), is | |
3801 | * possible. */ | |
3802 | bool | |
3803 | raft_may_snapshot(const struct raft *raft) | |
3804 | { | |
3805 | return (!raft->joining | |
3806 | && !raft->leaving | |
3807 | && !raft->left | |
3808 | && !raft->failed | |
3809 | && raft->last_applied >= raft->log_start); | |
3810 | } | |
3811 | ||
3812 | /* Replaces the log for 'raft', up to the last log entry read, by | |
3813 | * 'new_snapshot_data'. Returns NULL if successful, otherwise an error that | |
3814 | * the caller must eventually free. | |
3815 | * | |
3816 | * This function can only succeed if raft_may_snapshot() returns true. It is | |
3817 | * only valuable to call it if raft_get_log_length() is significant and | |
3818 | * especially if raft_grew_lots() returns true. */ | |
3819 | struct ovsdb_error * OVS_WARN_UNUSED_RESULT | |
3820 | raft_store_snapshot(struct raft *raft, const struct json *new_snapshot_data) | |
3821 | { | |
3822 | if (raft->joining) { | |
3823 | return ovsdb_error(NULL, | |
3824 | "cannot store a snapshot while joining cluster"); | |
3825 | } else if (raft->leaving) { | |
3826 | return ovsdb_error(NULL, | |
3827 | "cannot store a snapshot while leaving cluster"); | |
3828 | } else if (raft->left) { | |
3829 | return ovsdb_error(NULL, | |
3830 | "cannot store a snapshot after leaving cluster"); | |
3831 | } else if (raft->failed) { | |
3832 | return ovsdb_error(NULL, | |
3833 | "cannot store a snapshot following failure"); | |
3834 | } | |
3835 | ||
3836 | if (raft->last_applied < raft->log_start) { | |
3837 | return ovsdb_error(NULL, "not storing a duplicate snapshot"); | |
3838 | } | |
3839 | ||
3840 | uint64_t new_log_start = raft->last_applied + 1; | |
a521491b | 3841 | struct raft_entry new_snapshot = { |
1b1d2e6d | 3842 | .term = raft_get_term(raft, new_log_start - 1), |
a521491b | 3843 | .data = json_clone(new_snapshot_data), |
1b1d2e6d | 3844 | .eid = *raft_get_eid(raft, new_log_start - 1), |
a521491b | 3845 | .servers = json_clone(raft_servers_for_index(raft, new_log_start - 1)), |
1b1d2e6d BP |
3846 | }; |
3847 | struct ovsdb_error *error = raft_save_snapshot(raft, new_log_start, | |
3848 | &new_snapshot); | |
3849 | if (error) { | |
a521491b | 3850 | raft_entry_uninit(&new_snapshot); |
1b1d2e6d BP |
3851 | return error; |
3852 | } | |
3853 | ||
3854 | raft->log_synced = raft->log_end - 1; | |
3855 | raft_entry_uninit(&raft->snap); | |
a521491b | 3856 | raft->snap = new_snapshot; |
1b1d2e6d BP |
3857 | for (size_t i = 0; i < new_log_start - raft->log_start; i++) { |
3858 | raft_entry_uninit(&raft->entries[i]); | |
3859 | } | |
3860 | memmove(&raft->entries[0], &raft->entries[new_log_start - raft->log_start], | |
3861 | (raft->log_end - new_log_start) * sizeof *raft->entries); | |
3862 | raft->log_start = new_log_start; | |
3863 | return NULL; | |
3864 | } | |
3865 | ||
3866 | static void | |
3867 | raft_handle_become_leader(struct raft *raft, | |
3868 | const struct raft_become_leader *rq) | |
3869 | { | |
3870 | if (raft->role == RAFT_FOLLOWER) { | |
3871 | char buf[SID_LEN + 1]; | |
3872 | VLOG_INFO("received leadership transfer from %s in term %"PRIu64, | |
3873 | raft_get_nickname(raft, &rq->common.sid, buf, sizeof buf), | |
3874 | rq->term); | |
3875 | raft_start_election(raft, true); | |
3876 | } | |
3877 | } | |
3878 | ||
3879 | static void | |
3880 | raft_send_execute_command_reply(struct raft *raft, | |
3881 | const struct uuid *sid, | |
3882 | const struct uuid *eid, | |
3883 | enum raft_command_status status, | |
3884 | uint64_t commit_index) | |
3885 | { | |
3886 | union raft_rpc rpc = { | |
3887 | .execute_command_reply = { | |
3888 | .common = { | |
3889 | .type = RAFT_RPC_EXECUTE_COMMAND_REPLY, | |
3890 | .sid = *sid, | |
3891 | }, | |
3892 | .result = *eid, | |
3893 | .status = status, | |
3894 | .commit_index = commit_index, | |
3895 | }, | |
3896 | }; | |
3897 | raft_send(raft, &rpc); | |
3898 | } | |
3899 | ||
3900 | static enum raft_command_status | |
3901 | raft_handle_execute_command_request__( | |
3902 | struct raft *raft, const struct raft_execute_command_request *rq) | |
3903 | { | |
3904 | if (raft->role != RAFT_LEADER) { | |
3905 | return RAFT_CMD_NOT_LEADER; | |
3906 | } | |
3907 | ||
3908 | const struct uuid *current_eid = raft_current_eid(raft); | |
3909 | if (!uuid_equals(&rq->prereq, current_eid)) { | |
3910 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
3911 | VLOG_INFO_RL(&rl, "current entry eid "UUID_FMT" does not match " | |
3912 | "prerequisite "UUID_FMT" in execute_command_request", | |
3913 | UUID_ARGS(current_eid), UUID_ARGS(&rq->prereq)); | |
3914 | return RAFT_CMD_BAD_PREREQ; | |
3915 | } | |
3916 | ||
3917 | struct raft_command *cmd = raft_command_initiate(raft, rq->data, | |
3918 | NULL, &rq->result); | |
3919 | cmd->sid = rq->common.sid; | |
3920 | ||
3921 | enum raft_command_status status = cmd->status; | |
3922 | if (status != RAFT_CMD_INCOMPLETE) { | |
3923 | raft_command_unref(cmd); | |
3924 | } | |
3925 | return status; | |
3926 | } | |
3927 | ||
3928 | static void | |
3929 | raft_handle_execute_command_request( | |
3930 | struct raft *raft, const struct raft_execute_command_request *rq) | |
3931 | { | |
3932 | enum raft_command_status status | |
3933 | = raft_handle_execute_command_request__(raft, rq); | |
3934 | if (status != RAFT_CMD_INCOMPLETE) { | |
3935 | raft_send_execute_command_reply(raft, &rq->common.sid, &rq->result, | |
3936 | status, 0); | |
3937 | } | |
3938 | } | |
3939 | ||
3940 | static void | |
3941 | raft_handle_execute_command_reply( | |
3942 | struct raft *raft, const struct raft_execute_command_reply *rpy) | |
3943 | { | |
3944 | struct raft_command *cmd = raft_find_command_by_eid(raft, &rpy->result); | |
3945 | if (!cmd) { | |
3946 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5); | |
3947 | char buf[SID_LEN + 1]; | |
3948 | VLOG_INFO_RL(&rl, | |
3949 | "%s received \"%s\" reply from %s for unknown command", | |
3950 | raft->local_nickname, | |
3951 | raft_command_status_to_string(rpy->status), | |
3952 | raft_get_nickname(raft, &rpy->common.sid, | |
3953 | buf, sizeof buf)); | |
3954 | return; | |
3955 | } | |
3956 | ||
3957 | if (rpy->status == RAFT_CMD_INCOMPLETE) { | |
3958 | cmd->timestamp = time_msec(); | |
3959 | } else { | |
3960 | cmd->index = rpy->commit_index; | |
3961 | raft_command_complete(raft, cmd, rpy->status); | |
3962 | } | |
3963 | } | |
3964 | ||
3965 | static void | |
3966 | raft_handle_rpc(struct raft *raft, const union raft_rpc *rpc) | |
3967 | { | |
3968 | uint64_t term = raft_rpc_get_term(rpc); | |
3969 | if (term | |
3970 | && !raft_should_suppress_disruptive_server(raft, rpc) | |
3971 | && !raft_receive_term__(raft, &rpc->common, term)) { | |
3972 | if (rpc->type == RAFT_RPC_APPEND_REQUEST) { | |
3973 | /* Section 3.3: "If a server receives a request with a stale term | |
3974 | * number, it rejects the request." */ | |
3975 | raft_send_append_reply(raft, raft_append_request_cast(rpc), | |
3976 | RAFT_APPEND_INCONSISTENCY, "stale term"); | |
3977 | } | |
3978 | return; | |
3979 | } | |
3980 | ||
3981 | switch (rpc->type) { | |
3982 | #define RAFT_RPC(ENUM, NAME) \ | |
3983 | case ENUM: \ | |
3984 | raft_handle_##NAME(raft, &rpc->NAME); \ | |
3985 | break; | |
3986 | RAFT_RPC_TYPES | |
3987 | #undef RAFT_RPC | |
3988 | default: | |
3989 | OVS_NOT_REACHED(); | |
3990 | } | |
3991 | } | |
3992 | \f | |
3993 | static bool | |
3994 | raft_rpc_is_heartbeat(const union raft_rpc *rpc) | |
3995 | { | |
3996 | return ((rpc->type == RAFT_RPC_APPEND_REQUEST | |
3997 | || rpc->type == RAFT_RPC_APPEND_REPLY) | |
3998 | && rpc->common.comment | |
3999 | && !strcmp(rpc->common.comment, "heartbeat")); | |
4000 | } | |
4001 | ||
4002 | \f | |
4003 | static bool | |
4004 | raft_send__(struct raft *raft, const union raft_rpc *rpc, | |
4005 | struct raft_conn *conn) | |
4006 | { | |
4007 | log_rpc(rpc, "-->", conn); | |
4008 | return !jsonrpc_session_send( | |
4009 | conn->js, raft_rpc_to_jsonrpc(&raft->cid, &raft->sid, rpc)); | |
4010 | } | |
4011 | ||
4012 | static bool | |
4013 | raft_is_rpc_synced(const struct raft *raft, const union raft_rpc *rpc) | |
4014 | { | |
4015 | uint64_t term = raft_rpc_get_term(rpc); | |
4016 | uint64_t index = raft_rpc_get_min_sync_index(rpc); | |
4017 | const struct uuid *vote = raft_rpc_get_vote(rpc); | |
4018 | ||
4019 | return (term <= raft->synced_term | |
4020 | && index <= raft->log_synced | |
4021 | && (!vote || uuid_equals(vote, &raft->synced_vote))); | |
4022 | } | |
4023 | ||
4024 | static bool | |
4025 | raft_send(struct raft *raft, const union raft_rpc *rpc) | |
4026 | { | |
4027 | const struct uuid *dst = &rpc->common.sid; | |
4028 | if (uuid_equals(dst, &raft->sid)) { | |
4029 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 1); | |
4030 | VLOG_WARN_RL(&rl, "attempting to send RPC to self"); | |
4031 | return false; | |
4032 | } | |
4033 | ||
4034 | struct raft_conn *conn = raft_find_conn_by_sid(raft, dst); | |
4035 | if (!conn) { | |
4036 | static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 1); | |
4037 | char buf[SID_LEN + 1]; | |
4038 | VLOG_DBG_RL(&rl, "%s: no connection to %s, cannot send RPC", | |
4039 | raft->local_nickname, | |
4040 | raft_get_nickname(raft, dst, buf, sizeof buf)); | |
4041 | return false; | |
4042 | } | |
4043 | ||
4044 | if (!raft_is_rpc_synced(raft, rpc)) { | |
4045 | raft_waiter_create(raft, RAFT_W_RPC, false)->rpc = raft_rpc_clone(rpc); | |
4046 | return true; | |
4047 | } | |
4048 | ||
4049 | return raft_send__(raft, rpc, conn); | |
4050 | } | |
4051 | \f | |
4052 | static struct raft * | |
4053 | raft_lookup_by_name(const char *name) | |
4054 | { | |
4055 | struct raft *raft; | |
4056 | ||
4057 | HMAP_FOR_EACH_WITH_HASH (raft, hmap_node, hash_string(name, 0), | |
4058 | &all_rafts) { | |
4059 | if (!strcmp(raft->name, name)) { | |
4060 | return raft; | |
4061 | } | |
4062 | } | |
4063 | return NULL; | |
4064 | } | |
4065 | ||
4066 | static void | |
4067 | raft_unixctl_cid(struct unixctl_conn *conn, | |
4068 | int argc OVS_UNUSED, const char *argv[], | |
4069 | void *aux OVS_UNUSED) | |
4070 | { | |
4071 | struct raft *raft = raft_lookup_by_name(argv[1]); | |
4072 | if (!raft) { | |
4073 | unixctl_command_reply_error(conn, "unknown cluster"); | |
4074 | } else if (uuid_is_zero(&raft->cid)) { | |
4075 | unixctl_command_reply_error(conn, "cluster id not yet known"); | |
4076 | } else { | |
4077 | char *uuid = xasprintf(UUID_FMT, UUID_ARGS(&raft->cid)); | |
4078 | unixctl_command_reply(conn, uuid); | |
4079 | free(uuid); | |
4080 | } | |
4081 | } | |
4082 | ||
4083 | static void | |
4084 | raft_unixctl_sid(struct unixctl_conn *conn, | |
4085 | int argc OVS_UNUSED, const char *argv[], | |
4086 | void *aux OVS_UNUSED) | |
4087 | { | |
4088 | struct raft *raft = raft_lookup_by_name(argv[1]); | |
4089 | if (!raft) { | |
4090 | unixctl_command_reply_error(conn, "unknown cluster"); | |
4091 | } else { | |
4092 | char *uuid = xasprintf(UUID_FMT, UUID_ARGS(&raft->sid)); | |
4093 | unixctl_command_reply(conn, uuid); | |
4094 | free(uuid); | |
4095 | } | |
4096 | } | |
4097 | ||
4098 | static void | |
4099 | raft_put_sid(const char *title, const struct uuid *sid, | |
4100 | const struct raft *raft, struct ds *s) | |
4101 | { | |
4102 | ds_put_format(s, "%s: ", title); | |
4103 | if (uuid_equals(sid, &raft->sid)) { | |
4104 | ds_put_cstr(s, "self"); | |
4105 | } else if (uuid_is_zero(sid)) { | |
4106 | ds_put_cstr(s, "unknown"); | |
4107 | } else { | |
4108 | char buf[SID_LEN + 1]; | |
4109 | ds_put_cstr(s, raft_get_nickname(raft, sid, buf, sizeof buf)); | |
4110 | } | |
4111 | ds_put_char(s, '\n'); | |
4112 | } | |
4113 | ||
4114 | static void | |
4115 | raft_unixctl_status(struct unixctl_conn *conn, | |
4116 | int argc OVS_UNUSED, const char *argv[], | |
4117 | void *aux OVS_UNUSED) | |
4118 | { | |
4119 | struct raft *raft = raft_lookup_by_name(argv[1]); | |
4120 | if (!raft) { | |
4121 | unixctl_command_reply_error(conn, "unknown cluster"); | |
4122 | return; | |
4123 | } | |
4124 | ||
4125 | struct ds s = DS_EMPTY_INITIALIZER; | |
4126 | ds_put_format(&s, "%s\n", raft->local_nickname); | |
4127 | ds_put_format(&s, "Name: %s\n", raft->name); | |
4128 | ds_put_format(&s, "Cluster ID: "); | |
4129 | if (!uuid_is_zero(&raft->cid)) { | |
4130 | ds_put_format(&s, CID_FMT" ("UUID_FMT")\n", | |
4131 | CID_ARGS(&raft->cid), UUID_ARGS(&raft->cid)); | |
4132 | } else { | |
4133 | ds_put_format(&s, "not yet known\n"); | |
4134 | } | |
4135 | ds_put_format(&s, "Server ID: "SID_FMT" ("UUID_FMT")\n", | |
4136 | SID_ARGS(&raft->sid), UUID_ARGS(&raft->sid)); | |
4137 | ds_put_format(&s, "Address: %s\n", raft->local_address); | |
4138 | ds_put_format(&s, "Status: %s\n", | |
4139 | raft->joining ? "joining cluster" | |
4140 | : raft->leaving ? "leaving cluster" | |
4141 | : raft->left ? "left cluster" | |
4142 | : raft->failed ? "failed" | |
4143 | : "cluster member"); | |
4144 | if (raft->joining) { | |
4145 | ds_put_format(&s, "Remotes for joining:"); | |
4146 | const char *address; | |
4147 | SSET_FOR_EACH (address, &raft->remote_addresses) { | |
4148 | ds_put_format(&s, " %s", address); | |
4149 | } | |
4150 | ds_put_char(&s, '\n'); | |
4151 | } | |
4152 | if (raft->role == RAFT_LEADER) { | |
4153 | struct raft_server *as; | |
4154 | HMAP_FOR_EACH (as, hmap_node, &raft->add_servers) { | |
4155 | ds_put_format(&s, "Adding server %s ("SID_FMT" at %s) (%s)\n", | |
4156 | as->nickname, SID_ARGS(&as->sid), as->address, | |
4157 | raft_server_phase_to_string(as->phase)); | |
4158 | } | |
4159 | ||
4160 | struct raft_server *rs = raft->remove_server; | |
4161 | if (rs) { | |
4162 | ds_put_format(&s, "Removing server %s ("SID_FMT" at %s) (%s)\n", | |
4163 | rs->nickname, SID_ARGS(&rs->sid), rs->address, | |
4164 | raft_server_phase_to_string(rs->phase)); | |
4165 | } | |
4166 | } | |
4167 | ||
4168 | ds_put_format(&s, "Role: %s\n", | |
4169 | raft->role == RAFT_LEADER ? "leader" | |
4170 | : raft->role == RAFT_CANDIDATE ? "candidate" | |
4171 | : raft->role == RAFT_FOLLOWER ? "follower" | |
4172 | : "<error>"); | |
4173 | ds_put_format(&s, "Term: %"PRIu64"\n", raft->term); | |
4174 | raft_put_sid("Leader", &raft->leader_sid, raft, &s); | |
4175 | raft_put_sid("Vote", &raft->vote, raft, &s); | |
4176 | ds_put_char(&s, '\n'); | |
4177 | ||
4178 | ds_put_format(&s, "Log: [%"PRIu64", %"PRIu64"]\n", | |
4179 | raft->log_start, raft->log_end); | |
4180 | ||
4181 | uint64_t n_uncommitted = raft->log_end - raft->commit_index - 1; | |
4182 | ds_put_format(&s, "Entries not yet committed: %"PRIu64"\n", n_uncommitted); | |
4183 | ||
4184 | uint64_t n_unapplied = raft->log_end - raft->last_applied - 1; | |
4185 | ds_put_format(&s, "Entries not yet applied: %"PRIu64"\n", n_unapplied); | |
4186 | ||
4187 | const struct raft_conn *c; | |
4188 | ds_put_cstr(&s, "Connections:"); | |
4189 | LIST_FOR_EACH (c, list_node, &raft->conns) { | |
4190 | bool connected = jsonrpc_session_is_connected(c->js); | |
4191 | ds_put_format(&s, " %s%s%s%s", | |
4192 | connected ? "" : "(", | |
4193 | c->incoming ? "<-" : "->", c->nickname, | |
4194 | connected ? "" : ")"); | |
4195 | } | |
4196 | ds_put_char(&s, '\n'); | |
4197 | ||
4198 | ds_put_cstr(&s, "Servers:\n"); | |
4199 | struct raft_server *server; | |
4200 | HMAP_FOR_EACH (server, hmap_node, &raft->servers) { | |
4201 | ds_put_format(&s, " %s ("SID_FMT" at %s)", | |
4202 | server->nickname, | |
4203 | SID_ARGS(&server->sid), server->address); | |
4204 | if (uuid_equals(&server->sid, &raft->sid)) { | |
4205 | ds_put_cstr(&s, " (self)"); | |
4206 | } | |
4207 | if (server->phase != RAFT_PHASE_STABLE) { | |
4208 | ds_put_format (&s, " (%s)", | |
4209 | raft_server_phase_to_string(server->phase)); | |
4210 | } | |
4211 | if (raft->role == RAFT_CANDIDATE) { | |
4212 | if (!uuid_is_zero(&server->vote)) { | |
4213 | char buf[SID_LEN + 1]; | |
4214 | ds_put_format(&s, " (voted for %s)", | |
4215 | raft_get_nickname(raft, &server->vote, | |
4216 | buf, sizeof buf)); | |
4217 | } | |
4218 | } else if (raft->role == RAFT_LEADER) { | |
4219 | ds_put_format(&s, " next_index=%"PRIu64" match_index=%"PRIu64, | |
4220 | server->next_index, server->match_index); | |
4221 | } | |
4222 | ds_put_char(&s, '\n'); | |
4223 | } | |
4224 | ||
4225 | unixctl_command_reply(conn, ds_cstr(&s)); | |
4226 | ds_destroy(&s); | |
4227 | } | |
4228 | ||
4229 | static void | |
4230 | raft_unixctl_leave__(struct unixctl_conn *conn, struct raft *raft) | |
4231 | { | |
4232 | if (raft_is_leaving(raft)) { | |
4233 | unixctl_command_reply_error(conn, | |
4234 | "already in progress leaving cluster"); | |
4235 | } else if (raft_is_joining(raft)) { | |
4236 | unixctl_command_reply_error(conn, | |
4237 | "can't leave while join in progress"); | |
4238 | } else if (raft_failed(raft)) { | |
4239 | unixctl_command_reply_error(conn, | |
4240 | "can't leave after failure"); | |
4241 | } else { | |
4242 | raft_leave(raft); | |
4243 | unixctl_command_reply(conn, NULL); | |
4244 | } | |
4245 | } | |
4246 | ||
4247 | static void | |
4248 | raft_unixctl_leave(struct unixctl_conn *conn, int argc OVS_UNUSED, | |
4249 | const char *argv[], void *aux OVS_UNUSED) | |
4250 | { | |
4251 | struct raft *raft = raft_lookup_by_name(argv[1]); | |
4252 | if (!raft) { | |
4253 | unixctl_command_reply_error(conn, "unknown cluster"); | |
4254 | return; | |
4255 | } | |
4256 | ||
4257 | raft_unixctl_leave__(conn, raft); | |
4258 | } | |
4259 | ||
4260 | static struct raft_server * | |
4261 | raft_lookup_server_best_match(struct raft *raft, const char *id) | |
4262 | { | |
4263 | struct raft_server *best = NULL; | |
4264 | int best_score = -1; | |
4265 | int n_best = 0; | |
4266 | ||
4267 | struct raft_server *s; | |
4268 | HMAP_FOR_EACH (s, hmap_node, &raft->servers) { | |
4269 | int score = (!strcmp(id, s->address) | |
4270 | ? INT_MAX | |
4271 | : uuid_is_partial_match(&s->sid, id)); | |
4272 | if (score > best_score) { | |
4273 | best = s; | |
4274 | best_score = score; | |
4275 | n_best = 1; | |
4276 | } else if (score == best_score) { | |
4277 | n_best++; | |
4278 | } | |
4279 | } | |
4280 | return n_best == 1 ? best : NULL; | |
4281 | } | |
4282 | ||
4283 | static void | |
4284 | raft_unixctl_kick(struct unixctl_conn *conn, int argc OVS_UNUSED, | |
4285 | const char *argv[], void *aux OVS_UNUSED) | |
4286 | { | |
4287 | const char *cluster_name = argv[1]; | |
4288 | const char *server_name = argv[2]; | |
4289 | ||
4290 | struct raft *raft = raft_lookup_by_name(cluster_name); | |
4291 | if (!raft) { | |
4292 | unixctl_command_reply_error(conn, "unknown cluster"); | |
4293 | return; | |
4294 | } | |
4295 | ||
4296 | struct raft_server *server = raft_lookup_server_best_match(raft, | |
4297 | server_name); | |
4298 | if (!server) { | |
4299 | unixctl_command_reply_error(conn, "unknown server"); | |
4300 | return; | |
4301 | } | |
4302 | ||
4303 | if (uuid_equals(&server->sid, &raft->sid)) { | |
4304 | raft_unixctl_leave__(conn, raft); | |
4305 | } else if (raft->role == RAFT_LEADER) { | |
4306 | const struct raft_remove_server_request rq = { | |
4307 | .sid = server->sid, | |
4308 | .requester_conn = conn, | |
4309 | }; | |
4310 | raft_handle_remove_server_request(raft, &rq); | |
4311 | } else { | |
4312 | const union raft_rpc rpc = { | |
4313 | .remove_server_request = { | |
4314 | .common = { | |
4315 | .type = RAFT_RPC_REMOVE_SERVER_REQUEST, | |
4316 | .sid = raft->leader_sid, | |
4317 | .comment = "via unixctl" | |
4318 | }, | |
4319 | .sid = server->sid, | |
4320 | } | |
4321 | }; | |
4322 | if (raft_send(raft, &rpc)) { | |
4323 | unixctl_command_reply(conn, "sent removal request to leader"); | |
4324 | } else { | |
4325 | unixctl_command_reply_error(conn, | |
4326 | "failed to send removal request"); | |
4327 | } | |
4328 | } | |
4329 | } | |
4330 | ||
4331 | static void | |
4332 | raft_init(void) | |
4333 | { | |
4334 | static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER; | |
4335 | if (!ovsthread_once_start(&once)) { | |
4336 | return; | |
4337 | } | |
4338 | unixctl_command_register("cluster/cid", "DB", 1, 1, | |
4339 | raft_unixctl_cid, NULL); | |
4340 | unixctl_command_register("cluster/sid", "DB", 1, 1, | |
4341 | raft_unixctl_sid, NULL); | |
4342 | unixctl_command_register("cluster/status", "DB", 1, 1, | |
4343 | raft_unixctl_status, NULL); | |
4344 | unixctl_command_register("cluster/leave", "DB", 1, 1, | |
4345 | raft_unixctl_leave, NULL); | |
4346 | unixctl_command_register("cluster/kick", "DB SERVER", 2, 2, | |
4347 | raft_unixctl_kick, NULL); | |
4348 | ovsthread_once_done(&once); | |
4349 | } |