Redis Cluster provides automatic data sharding across multiple nodes with no single point of failure. This guide covers setup, resharding, and common operational tasks.
Redis Cluster Fundamentals
- Data is split into 16384 hash slots across master nodes
- Each master has one or more replicas for HA
- Minimum recommended: 3 masters + 3 replicas (6 nodes)
redis.conf for Cluster Mode
ini
port 7001
cluster-enabled yes
cluster-config-file nodes-7001.conf
cluster-node-timeout 5000
appendonly yes
appendfilename appendonly-7001.aof
save 900 1
save 300 10Create a 6-Node Cluster
bash
# Start 6 Redis instances on ports 7001-7006
for port in 7001 7002 7003 7004 7005 7006; do
redis-server /etc/redis/redis-$port.conf --daemonize yes
done
# Create cluster (--cluster-replicas 1 = 1 replica per master)
redis-cli --cluster create \
127.0.0.1:7001 127.0.0.1:7002 127.0.0.1:7003 \
127.0.0.1:7004 127.0.0.1:7005 127.0.0.1:7006 \
--cluster-replicas 1 --cluster-yesCheck Cluster Status
bash
redis-cli -p 7001 cluster info
redis-cli -p 7001 cluster nodes
# Detailed health check
redis-cli --cluster check 127.0.0.1:7001Add a New Master Node
bash
# Start new Redis instance on port 7007
redis-cli --cluster add-node 127.0.0.1:7007 127.0.0.1:7001
# Reshard to move slots to new master
redis-cli --cluster reshard 127.0.0.1:7001Manual Failover
bash
# Trigger failover from a replica
redis-cli -p 7004 cluster failover
# Force failover (even if master is reachable)
redis-cli -p 7004 cluster failover forceTip: Use
cluster failover (without FORCE) for planned maintenance — it waits until the replica is fully caught up before promoting, preventing data loss.Key Takeaways
- Minimum 3 masters ensures a quorum majority for cluster decisions
- Always provision replicas (--cluster-replicas 1) to survive node failures
- Use
redis-cli --cluster checkfor ongoing health verification - Prefer
cluster failoverover FORCE for planned switchovers
JusDB Can Help
Redis Cluster operations — resharding, node replacement, capacity planning — require expertise. JusDB supports Redis deployments at any scale.