Redis Replication Skill

Master-Replica Setup

Replica Configuration

replicaof master_ip 6379
masterauth your_password
replica-read-only yes
replica-serve-stale-data yes

Commands

REPLICAOF master_ip 6379   # Set master
REPLICAOF NO ONE           # Promote to master
INFO replication           # Check status

Sentinel (Auto-Failover)

Architecture

  Sentinel 1     Sentinel 2     Sentinel 3
      ↓              ↓              ↓
      └──────── Monitor ───────────┘
                   ↓
   Master ←──→ Replica 1 ←──→ Replica 2

Configuration

# sentinel.conf
port 26379
sentinel monitor mymaster 192.168.1.10 6379 2
sentinel auth-pass mymaster password
sentinel down-after-milliseconds mymaster 5000
sentinel failover-timeout mymaster 60000
sentinel parallel-syncs mymaster 1

Commands

# On Sentinel port
SENTINEL masters
SENTINEL get-master-addr-by-name mymaster
SENTINEL failover mymaster
SENTINEL replicas mymaster

Monitoring

INFO replication
# role:master|slave
# connected_slaves:2
# slave0:ip=...,port=...,state=online,offset=...,lag=0

Assets

• sentinel.conf - Sentinel configuration
• docker-compose-ha.yml - HA Docker setup

References

• REPLICATION_GUIDE.md - Setup guide

Troubleshooting

Replica Not Syncing

INFO replication  # Check master_link_status

Fix: Check network, password, and firewall

Split-Brain Prevention

min-replicas-to-write 1
min-replicas-max-lag 10

Failover Not Triggering

Check: Quorum (need majority of Sentinels)

Error Codes