lib/ovsdb-idl.h

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