How to fix ERR This instance is not in cluster mode in Redis

Connect to your Redis instance and verify the cluster setting:

redis-cli CONFIG GET cluster-enabled

If the response is (integer) 0, cluster mode is disabled.

Edit your redis.conf file and locate the cluster-enabled setting. Change it from no to yes:

cluster-enabled yes
cluster-config-file nodes.conf
cluster-node-timeout 5000
appendonly yes

The cluster-config-file specifies where Redis stores cluster state. The cluster-node-timeout is the maximum milliseconds a node can be unavailable before failover.

Stop and restart Redis to apply the configuration changes:

# If using systemd
sudo systemctl restart redis

# If running manually
pkill -f redis-server
redis-server /path/to/redis.conf

If you need an actual cluster, set up the minimum 3 master nodes and use redis-cli to initialize:

redis-cli --cluster create 127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002 --cluster-replicas 0

For production, Redis recommends at least 6 nodes (3 masters + 3 replicas).

Ensure your Redis client is configured for cluster mode if needed. For example, in Node.js with ioredis:

const Redis = require("ioredis");

const cluster = new Redis.Cluster(
  [
    { host: "127.0.0.1", port: 7000 },
    { host: "127.0.0.1", port: 7001 },
    { host: "127.0.0.1", port: 7002 },
  ],
  { enableReadyCheck: false }
);