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redis-sentinel

High availability monitoring for Redis clusters

TLDR

Start Sentinel with a config file
$ redis-sentinel [/etc/redis/sentinel.conf]
Start via redis-server in sentinel mode
$ redis-server [sentinel.conf] --sentinel
List all monitored masters
$ redis-cli -p [26379] sentinel masters
Get current master address by name
$ redis-cli -p [26379] sentinel get-master-addr-by-name [mymaster]
Trigger manual failover
$ redis-cli -p [26379] sentinel failover [mymaster]

SYNOPSIS

redis-sentinel configfile_redis-server configfile_ --sentinel

DESCRIPTION

Redis Sentinel provides high availability for Redis deployments through continuous monitoring, automatic failover, and notification. It watches master and replica instances, and when a master becomes unreachable and a quorum of Sentinel processes agree it is down, it automatically promotes a replica to master and reconfigures the remaining replicas to use the new master.Sentinel also acts as a configuration provider, allowing clients to discover the current master address for a named service. Multiple Sentinel instances (at least three are recommended) form a distributed system that reaches consensus on failover decisions, preventing split-brain scenarios.A configuration file is mandatory; Sentinel rewrites it on failover to persist the new topology.

PARAMETERS

--sentinel

When passed to `redis-server`, starts it in Sentinel mode using the provided config file.

INSTALL

sudo apt install redis-sentinel
sudo apk add valkey-compat

CAVEATS

At least three Sentinel instances are recommended for robust quorum. The default Sentinel port is 26379. Sentinel modifies its configuration file on failover. Sentinel does not shard data — it only monitors and redirects clients.

HISTORY

Redis Sentinel was introduced in Redis 2.4 (stable in 2.8) by Salvatore Sanfilippo to provide high availability without manual intervention.

SEE ALSO

redis-server(1), redis-cli(1)