How to Set Up Redis Cluster: Step-by-Step Guide

To set up a Redis Cluster, you need to start multiple Redis instances on different ports or servers, configure each with cluster-enabled settings, and then use the redis-cli --cluster create command to link them. This creates a distributed setup where data is automatically sharded and replicated across nodes.

Syntax

Setting up a Redis cluster involves these main steps:

• Start Redis instances: Run multiple Redis servers with cluster-enabled yes in their config files.
• Create the cluster: Use redis-cli --cluster create followed by the list of node addresses and ports.
• Assign slots: The cluster command automatically assigns hash slots to nodes for data distribution.

bash

redis-server /path/to/redis-node.conf

redis-cli --cluster create 127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002 --cluster-replicas 1

Example

This example shows how to start 3 Redis nodes locally and create a cluster with 1 replica per master node.

bash

# Create config files for each node with cluster enabled
cat > redis-7000.conf <<EOF
port 7000
cluster-enabled yes
cluster-config-file nodes-7000.conf
cluster-node-timeout 5000
dir ./7000
appendonly yes
EOF

cat > redis-7001.conf <<EOF
port 7001
cluster-enabled yes
cluster-config-file nodes-7001.conf
cluster-node-timeout 5000
dir ./7001
appendonly yes
EOF

cat > redis-7002.conf <<EOF
port 7002
cluster-enabled yes
cluster-config-file nodes-7002.conf
cluster-node-timeout 5000
dir ./7002
appendonly yes
EOF

# Start each Redis server in the background
redis-server redis-7000.conf &
redis-server redis-7001.conf &
redis-server redis-7002.conf &

# Create the cluster with 1 replica per master
redis-cli --cluster create 127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002 --cluster-replicas 1

Output

>>> Performing hash slots allocation on 3 nodes...
Master[0] -> Slots 0 - 5460
Master[1] -> Slots 5461 - 10922
Master[2] -> Slots 10923 - 16383
Adding replica 127.0.0.1:7001 to 127.0.0.1:7000
Adding replica 127.0.0.1:7002 to 127.0.0.1:7001
[OK] All nodes agree about slots configuration.

>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

>>> Nodes configuration updated
>>> Assign a different config epoch to each node
>>> Sending CLUSTER MEET messages to join the cluster

>>> Cluster created successfully!

Common Pitfalls

Common mistakes when setting up a Redis cluster include:

• Not enabling cluster-enabled yes in each node's config file.
• Using the same cluster-config-file name for multiple nodes, causing conflicts.
• Failing to open the required ports (default 7000-7005) in firewalls.
• Not starting enough nodes; a cluster needs at least 3 master nodes for fault tolerance.
• Incorrectly specifying node addresses in the redis-cli --cluster create command.

Example of a wrong config and the fix:

bash

# Wrong: cluster-enabled missing
port 7000
# cluster-enabled yes missing here
cluster-config-file nodes-7000.conf

# Right:
port 7000
cluster-enabled yes
cluster-config-file nodes-7000.conf

Quick Reference

Summary tips for Redis cluster setup:

• Run at least 3 master nodes for a stable cluster.
• Enable cluster-enabled yes in every node config.
• Use unique cluster-config-file names per node.
• Open all Redis ports (default 7000-7005) in your firewall.
• Use redis-cli --cluster create with all node addresses.

Key Takeaways

Enable cluster mode in each Redis node configuration with unique config files.

Start multiple Redis instances and connect them using redis-cli cluster create command.

Ensure at least 3 master nodes for fault tolerance and open required ports in firewall.

Use the --cluster-replicas option to add replicas for high availability.

Double-check node addresses and configs to avoid common setup errors.