lib/ovsdb-idl.h

   1 /* Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at:
   6  *
   7  *     http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  */
  15
  16 #ifndef OVSDB_IDL_H
  17 #define OVSDB_IDL_H 1
  18
  19 /* Open vSwitch Database Interface Definition Language (OVSDB IDL).
  20  *
  21  * The OVSDB IDL maintains an in-memory replica of a database.  It issues RPC
  22  * requests to an OVSDB database server and parses the responses, converting
  23  * raw JSON into data structures that are easier for clients to digest.  Most
  24  * notably, references to rows via UUID become C pointers.
  25  *
  26  * The IDL always presents a consistent snapshot of the database to its client,
  27  * that is, it won't present the effects of some part of a transaction applied
  28  * at the database server without presenting all of its effects.
  29  *
  30  * The IDL also assists with issuing database transactions.  The client creates
  31  * a transaction, manipulates the IDL data structures, and commits or aborts
  32  * the transaction.  The IDL then composes and issues the necessary JSON-RPC
  33  * requests and reports to the client whether the transaction completed
  34  * successfully.
  35  */
  36
  37 #include <stdbool.h>
  38 #include <stdint.h>
  39 #include "compiler.h"
  40 #include "ovsdb-types.h"
  41
  42 struct json;
  43 struct ovsdb_datum;
  44 struct ovsdb_idl_class;
  45 struct ovsdb_idl_column;
  46 struct ovsdb_idl_table_class;
  47 struct uuid;
  48
  49 struct ovsdb_idl *ovsdb_idl_create(const char *remote,
  50                                    const struct ovsdb_idl_class *,
  51                                    bool monitor_everything_by_default,
  52                                    bool retry);
  53 void ovsdb_idl_destroy(struct ovsdb_idl *);
  54
  55 void ovsdb_idl_run(struct ovsdb_idl *);
  56 void ovsdb_idl_wait(struct ovsdb_idl *);
  57
  58 void ovsdb_idl_set_lock(struct ovsdb_idl *, const char *lock_name);
  59 bool ovsdb_idl_has_lock(const struct ovsdb_idl *);
  60 bool ovsdb_idl_is_lock_contended(const struct ovsdb_idl *);
  61
  62 unsigned int ovsdb_idl_get_seqno(const struct ovsdb_idl *);
  63 bool ovsdb_idl_has_ever_connected(const struct ovsdb_idl *);
  64 void ovsdb_idl_enable_reconnect(struct ovsdb_idl *);
  65 void ovsdb_idl_force_reconnect(struct ovsdb_idl *);
  66 void ovsdb_idl_verify_write_only(struct ovsdb_idl *);
  67
  68 bool ovsdb_idl_is_alive(const struct ovsdb_idl *);
  69 int ovsdb_idl_get_last_error(const struct ovsdb_idl *);
  70 \f
  71 /* Choosing columns and tables to replicate. */
  72
  73 /* Modes with which the IDL can monitor a column.
  74  *
  75  * If no bits are set, the column is not monitored at all.  Its value will
  76  * always appear to the client to be the default value for its type.
  77  *
  78  * If OVSDB_IDL_MONITOR is set, then the column is replicated.  Its value will
  79  * reflect the value in the database.  If OVSDB_IDL_ALERT is also set, then the
  80  * value returned by ovsdb_idl_get_seqno() will change when the column's value
  81  * changes.
  82  *
  83  * The possible mode combinations are:
  84  *
  85  *   - 0, for a column that a client doesn't care about.
  86  *
  87  *   - (OVSDB_IDL_MONITOR | OVSDB_IDL_ALERT), for a column that a client wants
  88  *     to track and possibly update.
  89  *
  90  *   - OVSDB_IDL_MONITOR, for columns that a client treats as "write-only",
  91  *     that is, it updates them but doesn't want to get alerted about its own
  92  *     updates.  It also won't be alerted about other clients' updates, so this
  93  *     is suitable only for use by a client that "owns" a particular column.
  94  *
  95  *   - OVDSB_IDL_ALERT without OVSDB_IDL_MONITOR is not valid.
  96  */
  97 #define OVSDB_IDL_MONITOR (1 << 0) /* Monitor this column? */
  98 #define OVSDB_IDL_ALERT   (1 << 1) /* Alert client when column updated? */
  99
 100 void ovsdb_idl_add_column(struct ovsdb_idl *, const struct ovsdb_idl_column *);
 101 void ovsdb_idl_add_table(struct ovsdb_idl *,
 102                          const struct ovsdb_idl_table_class *);
 103
 104 void ovsdb_idl_omit(struct ovsdb_idl *, const struct ovsdb_idl_column *);
 105 void ovsdb_idl_omit_alert(struct ovsdb_idl *, const struct ovsdb_idl_column *);
 106 \f
 107 /* Reading the database replica. */
 108
 109 const struct ovsdb_idl_row *ovsdb_idl_get_row_for_uuid(
 110     const struct ovsdb_idl *, const struct ovsdb_idl_table_class *,
 111     const struct uuid *);
 112 const struct ovsdb_idl_row *ovsdb_idl_first_row(
 113     const struct ovsdb_idl *, const struct ovsdb_idl_table_class *);
 114 const struct ovsdb_idl_row *ovsdb_idl_next_row(const struct ovsdb_idl_row *);
 115
 116 const struct ovsdb_datum *ovsdb_idl_read(const struct ovsdb_idl_row *,
 117                                          const struct ovsdb_idl_column *);
 118 const struct ovsdb_datum *ovsdb_idl_get(const struct ovsdb_idl_row *,
 119                                         const struct ovsdb_idl_column *,
 120                                         enum ovsdb_atomic_type key_type,
 121                                         enum ovsdb_atomic_type value_type);
 122 bool ovsdb_idl_is_mutable(const struct ovsdb_idl_row *,
 123                           const struct ovsdb_idl_column *);
 124
 125 bool ovsdb_idl_row_is_synthetic(const struct ovsdb_idl_row *);
 126 \f
 127 /* Transactions.
 128  *
 129  * A transaction may modify the contents of a database by modifying the values
 130  * of columns, deleting rows, inserting rows, or adding checks that columns in
 131  * the database have not changed ("verify" operations), through
 132  * ovsdb_idl_txn_*() functions.  (The OVSDB IDL code generator produces helper
 133  * functions that internally call the ovsdb_idl_txn_*() functions.  These are
 134  * likely to be more convenient.)
 135  *
 136  * Reading and writing columns and inserting and deleting rows are all
 137  * straightforward.  The reasons to verify columns are less obvious.
 138  * Verification is the key to maintaining transactional integrity.  Because
 139  * OVSDB handles multiple clients, it can happen that between the time that
 140  * OVSDB client A reads a column and writes a new value, OVSDB client B has
 141  * written that column.  Client A's write should not ordinarily overwrite
 142  * client B's, especially if the column in question is a "map" column that
 143  * contains several more or less independent data items.  If client A adds a
 144  * "verify" operation before it writes the column, then the transaction fails
 145  * in case client B modifies it first.  Client A will then see the new value of
 146  * the column and compose a new transaction based on the new contents written
 147  * by client B.
 148  *
 149  * When a transaction is complete, which must be before the next call to
 150  * ovsdb_idl_run() on 'idl', call ovsdb_idl_txn_commit() or
 151  * ovsdb_idl_txn_abort().
 152  *
 153  * The life-cycle of a transaction looks like this:
 154  *
 155  * 1. Create the transaction and record the initial sequence number:
 156  *
 157  *     seqno = ovsdb_idl_get_seqno(idl);
 158  *     txn = ovsdb_idl_txn_create(idl);
 159  *
 160  * 2. Modify the database with ovsdb_idl_txn_*() functions directly or
 161  *    indirectly.
 162  *
 163  * 3. Commit the transaction by calling ovsdb_idl_txn_commit().  The first call
 164  *    to this function probably returns TXN_INCOMPLETE.  The client must keep
 165  *    calling again along as this remains true, calling ovsdb_idl_run() in
 166  *    between to let the IDL do protocol processing.  (If the client doesn't
 167  *    have anything else to do in the meantime, it can use
 168  *    ovsdb_idl_txn_commit_block() to avoid having to loop itself.)
 169  *
 170  * 4. If the final status is TXN_TRY_AGAIN, wait for ovsdb_idl_get_seqno() to
 171  *    change from the saved 'seqno' (it's possible that it's already changed,
 172  *    in which case the client should not wait at all), then start over from
 173  *    step 1.  Only a call to ovsdb_idl_run() will change the return value of
 174  *    ovsdb_idl_get_seqno().  (ovsdb_idl_txn_commit_block() calls
 175  *    ovsdb_idl_run().)
 176  */
 177
 178 enum ovsdb_idl_txn_status {
 179     TXN_UNCOMMITTED,            /* Not yet committed or aborted. */
 180     TXN_UNCHANGED,              /* Transaction didn't include any changes. */
 181     TXN_INCOMPLETE,             /* Commit in progress, please wait. */
 182     TXN_ABORTED,                /* ovsdb_idl_txn_abort() called. */
 183     TXN_SUCCESS,                /* Commit successful. */
 184     TXN_TRY_AGAIN,              /* Commit failed because a "verify" operation
 185                                  * reported an inconsistency, due to a network
 186                                  * problem, or other transient failure.  Wait
 187                                  * for a change, then try again. */
 188     TXN_NOT_LOCKED,             /* Server hasn't given us the lock yet. */
 189     TXN_ERROR                   /* Commit failed due to a hard error. */
 190 };
 191
 192 const char *ovsdb_idl_txn_status_to_string(enum ovsdb_idl_txn_status);
 193
 194 struct ovsdb_idl_txn *ovsdb_idl_txn_create(struct ovsdb_idl *);
 195 void ovsdb_idl_txn_add_comment(struct ovsdb_idl_txn *, const char *, ...)
 196     OVS_PRINTF_FORMAT (2, 3);
 197 void ovsdb_idl_txn_set_dry_run(struct ovsdb_idl_txn *);
 198 void ovsdb_idl_txn_increment(struct ovsdb_idl_txn *,
 199                              const struct ovsdb_idl_row *,
 200                              const struct ovsdb_idl_column *);
 201 void ovsdb_idl_txn_destroy(struct ovsdb_idl_txn *);
 202 void ovsdb_idl_txn_wait(const struct ovsdb_idl_txn *);
 203 enum ovsdb_idl_txn_status ovsdb_idl_txn_commit(struct ovsdb_idl_txn *);
 204 enum ovsdb_idl_txn_status ovsdb_idl_txn_commit_block(struct ovsdb_idl_txn *);
 205 void ovsdb_idl_txn_abort(struct ovsdb_idl_txn *);
 206
 207 const char *ovsdb_idl_txn_get_error(const struct ovsdb_idl_txn *);
 208
 209 int64_t ovsdb_idl_txn_get_increment_new_value(const struct ovsdb_idl_txn *);
 210 const struct uuid *ovsdb_idl_txn_get_insert_uuid(const struct ovsdb_idl_txn *,
 211                                                  const struct uuid *);
 212
 213 void ovsdb_idl_txn_write(const struct ovsdb_idl_row *,
 214                          const struct ovsdb_idl_column *,
 215                          struct ovsdb_datum *);
 216 void ovsdb_idl_txn_write_clone(const struct ovsdb_idl_row *,
 217                                const struct ovsdb_idl_column *,
 218                                const struct ovsdb_datum *);
 219 void ovsdb_idl_txn_delete(const struct ovsdb_idl_row *);
 220 const struct ovsdb_idl_row *ovsdb_idl_txn_insert(
 221     struct ovsdb_idl_txn *, const struct ovsdb_idl_table_class *,
 222     const struct uuid *);
 223
 224 struct ovsdb_idl *ovsdb_idl_txn_get_idl (struct ovsdb_idl_txn *);
 225 \f
 226
 227 /* ovsdb_idl_loop provides an easy way to manage the transactions related
 228  * to 'idl' and to cope with different status during transaction. */
 229 struct ovsdb_idl_loop {
 230     struct ovsdb_idl *idl;
 231     unsigned int skip_seqno;
 232
 233     struct ovsdb_idl_txn *committing_txn;
 234     unsigned int precommit_seqno;
 235
 236     struct ovsdb_idl_txn *open_txn;
 237 };
 238
 239 #define OVSDB_IDL_LOOP_INITIALIZER(IDL) { .idl = (IDL) }
 240
 241 void ovsdb_idl_loop_destroy(struct ovsdb_idl_loop *);
 242 struct ovsdb_idl_txn *ovsdb_idl_loop_run(struct ovsdb_idl_loop *);
 243 void ovsdb_idl_loop_commit_and_wait(struct ovsdb_idl_loop *);
 244
 245 #endif /* ovsdb-idl.h */