ovs/lib/ovsdb-idl.h

/* Copyright (c) 2009, 2010, 2011, 2012 Nicira, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef OVSDB_IDL_H
#define OVSDB_IDL_H 1

/* Open vSwitch Database Interface Definition Language (OVSDB IDL).
 *
 * The OVSDB IDL maintains an in-memory replica of a database.  It issues RPC
 * requests to an OVSDB database server and parses the responses, converting
 * raw JSON into data structures that are easier for clients to digest.  Most
 * notably, references to rows via UUID become C pointers.
 *
 * The IDL also assists with issuing database transactions.  The client creates
 * a transaction, manipulates the IDL data structures, and commits or aborts
 * the transaction.  The IDL then composes and issues the necessary JSON-RPC
 * requests and reports to the client whether the transaction completed
 * successfully.
 */

#include <stdbool.h>
#include <stdint.h>
#include "compiler.h"
#include "ovsdb-types.h"

struct json;
struct ovsdb_datum;
struct ovsdb_idl_class;
struct ovsdb_idl_column;
struct ovsdb_idl_table_class;
struct uuid;

struct ovsdb_idl *ovsdb_idl_create(const char *remote,
                                   const struct ovsdb_idl_class *,
                                   bool monitor_everything_by_default);
void ovsdb_idl_destroy(struct ovsdb_idl *);

void ovsdb_idl_run(struct ovsdb_idl *);
void ovsdb_idl_wait(struct ovsdb_idl *);

void ovsdb_idl_set_lock(struct ovsdb_idl *, const char *lock_name);
bool ovsdb_idl_has_lock(const struct ovsdb_idl *);
bool ovsdb_idl_is_lock_contended(const struct ovsdb_idl *);

unsigned int ovsdb_idl_get_seqno(const struct ovsdb_idl *);
bool ovsdb_idl_has_ever_connected(const struct ovsdb_idl *);
void ovsdb_idl_force_reconnect(struct ovsdb_idl *);

/* Choosing columns and tables to replicate. */

/* Modes with which the IDL can monitor a column.
 *
 * If no bits are set, the column is not monitored at all.  Its value will
 * always appear to the client to be the default value for its type.
 *
 * If OVSDB_IDL_MONITOR is set, then the column is replicated.  Its value will
 * reflect the value in the database.  If OVSDB_IDL_ALERT is also set, then the
 * value returned by ovsdb_idl_get_seqno() will change when the column's value
 * changes.
 *
 * The possible mode combinations are:
 *
 *   - 0, for a column that a client doesn't care about.
 *
 *   - (OVSDB_IDL_MONITOR | OVSDB_IDL_ALERT), for a column that a client wants
 *     to track and possibly update.
 *
 *   - OVSDB_IDL_MONITOR, for columns that a client treats as "write-only",
 *     that is, it updates them but doesn't want to get alerted about its own
 *     updates.  It also won't be alerted about other clients' updates, so this
 *     is suitable only for use by a client that "owns" a particular column.
 *
 *   - OVDSB_IDL_ALERT without OVSDB_IDL_MONITOR is not valid.
 */
#define OVSDB_IDL_MONITOR (1 << 0) /* Monitor this column? */
#define OVSDB_IDL_ALERT   (1 << 1) /* Alert client when column updated? */

void ovsdb_idl_add_column(struct ovsdb_idl *, const struct ovsdb_idl_column *);
void ovsdb_idl_add_table(struct ovsdb_idl *,
                         const struct ovsdb_idl_table_class *);

void ovsdb_idl_omit(struct ovsdb_idl *, const struct ovsdb_idl_column *);
void ovsdb_idl_omit_alert(struct ovsdb_idl *, const struct ovsdb_idl_column *);

/* Reading the database replica. */

const struct ovsdb_idl_row *ovsdb_idl_get_row_for_uuid(
    const struct ovsdb_idl *, const struct ovsdb_idl_table_class *,
    const struct uuid *);
const struct ovsdb_idl_row *ovsdb_idl_first_row(
    const struct ovsdb_idl *, const struct ovsdb_idl_table_class *);
const struct ovsdb_idl_row *ovsdb_idl_next_row(const struct ovsdb_idl_row *);

const struct ovsdb_datum *ovsdb_idl_read(const struct ovsdb_idl_row *,
                                         const struct ovsdb_idl_column *);
const struct ovsdb_datum *ovsdb_idl_get(const struct ovsdb_idl_row *,
                                        const struct ovsdb_idl_column *,
                                        enum ovsdb_atomic_type key_type,
                                        enum ovsdb_atomic_type value_type);

bool ovsdb_idl_row_is_synthetic(const struct ovsdb_idl_row *);

/* Transactions.
 *
 * A transaction may modify the contents of a database by modifying the values
 * of columns, deleting rows, inserting rows, or adding checks that columns in
 * the database have not changed ("verify" operations), through
 * ovsdb_idl_txn_*() functions.  (The OVSDB IDL code generator produces helper
 * functions that internally call the ovsdb_idl_txn_*() functions.  These are
 * likely to be more convenient.)
 *
 * Reading and writing columns and inserting and deleting rows are all
 * straightforward.  The reasons to verify columns are less obvious.
 * Verification is the key to maintaining transactional integrity.  Because
 * OVSDB handles multiple clients, it can happen that between the time that
 * OVSDB client A reads a column and writes a new value, OVSDB client B has
 * written that column.  Client A's write should not ordinarily overwrite
 * client B's, especially if the column in question is a "map" column that
 * contains several more or less independent data items.  If client A adds a
 * "verify" operation before it writes the column, then the transaction fails
 * in case client B modifies it first.  Client A will then see the new value of
 * the column and compose a new transaction based on the new contents written
 * by client B.
 *
 * When a transaction is complete, which must be before the next call to
 * ovsdb_idl_run() on 'idl', call ovsdb_idl_txn_commit() or
 * ovsdb_idl_txn_abort().
 *
 * The life-cycle of a transaction looks like this:
 *
 * 1. Create the transaction and record the initial sequence number:
 *
 *     seqno = ovsdb_idl_get_seqno(idl);
 *     txn = ovsdb_idl_txn_create(idl);
 *
 * 2. Modify the database with ovsdb_idl_txn_*() functions directly or
 *    indirectly.
 *
 * 3. Commit the transaction by calling ovsdb_idl_txn_commit().  The first call
 *    to this function probably returns TXN_INCOMPLETE.  The client must keep
 *    calling again along as this remains true, calling ovsdb_idl_run() in
 *    between to let the IDL do protocol processing.  (If the client doesn't
 *    have anything else to do in the meantime, it can use
 *    ovsdb_idl_txn_commit_block() to avoid having to loop itself.)
 *
 * 4. If the final status is TXN_TRY_AGAIN, wait for ovsdb_idl_get_seqno() to
 *    change from the saved 'seqno' (it's possible that it's already changed,
 *    in which case the client should not wait at all), then start over from
 *    step 1.  Only a call to ovsdb_idl_run() will change the return value of
 *    ovsdb_idl_get_seqno().  (ovsdb_idl_txn_commit_block() calls
 *    ovsdb_idl_run().)
 */

enum ovsdb_idl_txn_status {
    TXN_UNCOMMITTED,            /* Not yet committed or aborted. */
    TXN_UNCHANGED,              /* Transaction didn't include any changes. */
    TXN_INCOMPLETE,             /* Commit in progress, please wait. */
    TXN_ABORTED,                /* ovsdb_idl_txn_abort() called. */
    TXN_SUCCESS,                /* Commit successful. */
    TXN_TRY_AGAIN,              /* Commit failed because a "verify" operation
                                 * reported an inconsistency, due to a network
                                 * problem, or other transient failure.  Wait
                                 * for a change, then try again. */
    TXN_NOT_LOCKED,             /* Server hasn't given us the lock yet. */
    TXN_ERROR                   /* Commit failed due to a hard error. */
};

const char *ovsdb_idl_txn_status_to_string(enum ovsdb_idl_txn_status);

struct ovsdb_idl_txn *ovsdb_idl_txn_create(struct ovsdb_idl *);
void ovsdb_idl_txn_add_comment(struct ovsdb_idl_txn *, const char *, ...)
    PRINTF_FORMAT (2, 3);
void ovsdb_idl_txn_set_dry_run(struct ovsdb_idl_txn *);
void ovsdb_idl_txn_increment(struct ovsdb_idl_txn *,
                             const struct ovsdb_idl_row *,
                             const struct ovsdb_idl_column *);
void ovsdb_idl_txn_destroy(struct ovsdb_idl_txn *);
void ovsdb_idl_txn_wait(const struct ovsdb_idl_txn *);
enum ovsdb_idl_txn_status ovsdb_idl_txn_commit(struct ovsdb_idl_txn *);
enum ovsdb_idl_txn_status ovsdb_idl_txn_commit_block(struct ovsdb_idl_txn *);
void ovsdb_idl_txn_abort(struct ovsdb_idl_txn *);

const char *ovsdb_idl_txn_get_error(const struct ovsdb_idl_txn *);

int64_t ovsdb_idl_txn_get_increment_new_value(const struct ovsdb_idl_txn *);
const struct uuid *ovsdb_idl_txn_get_insert_uuid(const struct ovsdb_idl_txn *,
                                                 const struct uuid *);

void ovsdb_idl_txn_write(const struct ovsdb_idl_row *,
                         const struct ovsdb_idl_column *,
                         struct ovsdb_datum *);
void ovsdb_idl_txn_delete(const struct ovsdb_idl_row *);
const struct ovsdb_idl_row *ovsdb_idl_txn_insert(
    struct ovsdb_idl_txn *, const struct ovsdb_idl_table_class *,
    const struct uuid *);

struct ovsdb_idl *ovsdb_idl_txn_get_idl (struct ovsdb_idl_txn *);

#endif /* ovsdb-idl.h */