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