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Redis Sentinel

Redis Sentinel provides high availability for Redis. In practical terms this means that using Sentinel you can create a Redis deployment that resists without human intervention certain kinds of failures.

Redis Sentinel also provides other collateral tasks such as monitoring, notifications and acts as a configuration provider for clients.

Class RedisSentinel

Parameters

host: String, IP address or hostname
port: Int (optional, default is 26379)
timeout: Float, value in seconds (optional, default is 0 meaning unlimited)
persistent: String, persistent connection id (optional, default is NULL meaning not persistent)
retry_interval: Int, value in milliseconds (optional, default is 0)
read_timeout: Float, value in seconds (optional, default is 0 meaning unlimited)

Example
$sentinel = new RedisSentinel('127.0.0.1'); // default parameters
$sentinel = new RedisSentinel('127.0.0.1', 26379, 2.5); // 2.5 sec timeout.
$sentinel = new RedisSentinel('127.0.0.1', 26379, 0, 'sentinel'); // persistent connection with id 'sentinel'
$sentinel = new RedisSentinel('127.0.0.1', 26379, 0, ''); // also persistent connection with id ''
$sentinel = new RedisSentinel('127.0.0.1', 26379, 1, null, 100); // 1 sec timeout, 100ms delay between reconnection attempts.

Usage

  • ckquorum - Check if the current Sentinel configuration is able to reach the quorum needed to failover.
  • failover - Force a failover as if the master was not reachable.
  • flushconfig - Force Sentinel to rewrite its configuration on disk.
  • getMasterAddrByName - Return the ip and port number of the master with that name.
  • master - Return the state and info of the specified master.
  • masters - Return a list of monitored masters and their state.
  • ping - Ping the sentinel.
  • reset - Reset all the masters with matching name.
  • sentinels - Return a list of sentinel instances for this master, and their state.
  • slaves - Return a list of replicas for this master, and their state.

ckquorum

Description: Check if the current Sentinel configuration is able to reach the quorum needed to failover a master, and the majority needed to authorize the failover. This command should be used in monitoring systems to check if a Sentinel deployment is ok.

Parameters

String: master name

Return value

Bool: TRUE in case of success, FALSE in case of failure.

Example
$sentinel->ckquorum('mymaster');

failover

Description: Force a failover as if the master was not reachable, and without asking for agreement to other Sentinels (however a new version of the configuration will be published so that the other Sentinels will update their configurations).

Parameters

String: master name

Return value

Bool: TRUE in case of success, FALSE in case of failure.

Example
$sentinel->failover('mymaster');

flushconfig

Description: Force Sentinel to rewrite its configuration on disk, including the current Sentinel state. Normally Sentinel rewrites the configuration every time something changes in its state (in the context of the subset of the state which is persisted on disk across restart). However sometimes it is possible that the configuration file is lost because of operation errors, disk failures, package upgrade scripts or configuration managers. In those cases a way to to force Sentinel to rewrite the configuration file is handy. This command works even if the previous configuration file is completely missing.

Parameters

(none)

Return value

Bool: TRUE in case of success, FALSE in case of failure.

Example
$sentinel->flushconfig();

getMasterAddrByName

Description: Return the ip and port number of the master with that name. If a failover is in progress or terminated successfully for this master it returns the address and port of the promoted replica.

Parameters

String: master name

Return value

Array, Bool: ['address', 'port'] in case of success, FALSE in case of failure.

Example
$sentinel->getMasterAddrByName('mymaster');

master

Description: Return the state and info of the specified master.

Parameters

String: master name

Return value

Array, Bool: Associative array with info in case of success, FALSE in case of failure.

Example
$sentinel->master('mymaster');

masters

Description: Return a list of monitored masters and their state.

Parameters

(none)

Return value

Array, Bool: List of arrays with info for each master in case of success, FALSE in case of failure.

Example
$sentinel->masters();

ping

Description: Ping the sentinel.

Parameters

(none)

Return value

Bool: TRUE in case of success, FALSE in case of failure.

Example
$sentinel->ping();

reset

Description: This command will reset all the masters with matching name. The pattern argument is a glob-style pattern. The reset process clears any previous state in a master (including a failover in progress), and removes every replica and sentinel already discovered and associated with the master.

Parameters

String: pattern

Return value

Bool: TRUE in case of success, FALSE in case of failure.

Example
$sentinel->reset('*');

sentinels

Description: Return a list of sentinel instances for this master, and their state.

Parameters

String: master name

Return value

Array, Bool: List of arrays with info for each sentinels in case of success, FALSE in case of failure.

Example
$sentinel->sentinels('mymaster');

slaves

Description: Return a list of replicas for this master, and their state.

Parameters

String: master name

Return value

Array, Bool: List of arrays with info for each replicas in case of success, FALSE in case of failure.

Example
$sentinel->slaves('mymaster');