lib/ovsdb-idl.h

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