Sentinel

Sentinel Commands

rLightning Sentinel provides high availability through master monitoring, automatic failover, and configuration provider services. Sentinel monitors master and replica instances, detects failures via quorum-based voting, and promotes replicas when a master becomes unavailable.

SENTINEL MASTERS

Synopsis: SENTINEL MASTERS

Return a list of all monitored masters and their current state.

> SENTINEL MASTERS
1)  1) "name"
    2) "mymaster"
    3) "ip"
    4) "127.0.0.1"
    5) "port"
    6) (integer) 6379
    7) "flags"
    8) "master"
    9) "num-slaves"
   10) (integer) 2
   11) "num-other-sentinels"
   12) (integer) 2
   13) "quorum"
   14) (integer) 2
   ...

SENTINEL MASTER

Synopsis: SENTINEL MASTER master-name

Return the state and information of the specified master.

> SENTINEL MASTER mymaster
 1) "name"
 2) "mymaster"
 3) "ip"
 4) "127.0.0.1"
 5) "port"
 6) (integer) 6379
 ...

SENTINEL REPLICAS

Synopsis: SENTINEL REPLICAS master-name

Return a list of replica instances for the specified master and their state.

> SENTINEL REPLICAS mymaster
1)  1) "name"
    2) "127.0.0.1:6380"
    3) "ip"
    4) "127.0.0.1"
    5) "port"
    6) (integer) 6380
    7) "flags"
    8) "slave"
    ...

SENTINEL SLAVES

Synopsis: SENTINEL SLAVES master-name

Deprecated alias for SENTINEL REPLICAS.

> SENTINEL SLAVES mymaster
(same output as SENTINEL REPLICAS)

SENTINEL GET-MASTER-ADDR-BY-NAME

Synopsis: SENTINEL GET-MASTER-ADDR-BY-NAME master-name

Return the IP address and port of the current master for the given name. This is the primary command used by clients to discover the current master.

> SENTINEL GET-MASTER-ADDR-BY-NAME mymaster
1) "127.0.0.1"
2) "6379"

SENTINEL IS-MASTER-DOWN-BY-ADDR

Synopsis: SENTINEL IS-MASTER-DOWN-BY-ADDR ip port current-epoch runid

Used internally by Sentinels to check if a master is down and to request votes during failover leader election.

> SENTINEL IS-MASTER-DOWN-BY-ADDR 127.0.0.1 6379 0 *
1) (integer) 0
2) "*"
3) (integer) 0

SENTINEL MONITOR

Synopsis: SENTINEL MONITOR master-name ip port quorum

Start monitoring a new master with the given name, address, and quorum.

> SENTINEL MONITOR mymaster 127.0.0.1 6379 2
OK

SENTINEL SET

Synopsis: SENTINEL SET master-name option value [option value ...]

Change the configuration of a monitored master at runtime.

Common options:

• down-after-milliseconds — Time before considering a master as down.
• failover-timeout — Timeout for failover operations.
• parallel-syncs — Number of replicas to reconfigure simultaneously during failover.

> SENTINEL SET mymaster down-after-milliseconds 5000
OK
> SENTINEL SET mymaster failover-timeout 60000
OK

SENTINEL REMOVE

Synopsis: SENTINEL REMOVE master-name

Stop monitoring the specified master.

> SENTINEL REMOVE mymaster
OK

SENTINEL FAILOVER

Synopsis: SENTINEL FAILOVER master-name

Trigger a manual failover for the specified master. A replica is promoted to master without agreement from other Sentinels.

> SENTINEL FAILOVER mymaster
OK

SENTINEL PENDING-SCRIPTS

Synopsis: SENTINEL PENDING-SCRIPTS

Return a list of pending scripts (notification and reconfig scripts) that have not yet completed.

> SENTINEL PENDING-SCRIPTS
(empty array)

SENTINEL CKQUORUM

Synopsis: SENTINEL CKQUORUM master-name

Check if the current Sentinel configuration is able to reach the quorum needed to authorize a failover and the majority needed to authorize the configuration change.

> SENTINEL CKQUORUM mymaster
OK 3 usable Sentinels. Quorum and samples are reachable.

SENTINEL FLUSHCONFIG

Synopsis: SENTINEL FLUSHCONFIG

Force Sentinel to rewrite its configuration on disk, including the current state.

> SENTINEL FLUSHCONFIG
OK