clustering.md

Clustering

Basic Example

Connecting to a cluster is a bit different. Create the client by specifying some (or all) of the nodes in your cluster and then use it like a regular client instance:

import { createCluster } from 'redis';

(async () => {
  const cluster = createCluster({
    rootNodes: [
      {
        url: 'redis://10.0.0.1:30001'
      },
      {
        url: 'redis://10.0.0.2:30002'
      }
    ]
  });

  cluster.on('error', (err) => console.log('Redis Cluster Error', err));

  await cluster.connect();

  await cluster.set('key', 'value');
  const value = await cluster.get('key');
})();

createCluster configuration

See the client configuration page for the rootNodes and defaults configuration schemas.

Property	Default	Description
rootNodes		An array of root nodes that are part of the cluster, which will be used to get the cluster topology. Each element in the array is a client configuration object. There is no need to specify every node in the cluster, 3 should be enough to reliably connect and obtain the cluster configuration from the server
defaults		The default configuration values for every client in the cluster. Use this for example when specifying an ACL user to connect with
useReplicas	false	When true, distribute load by executing readonly commands (such as GET, GEOSEARCH, etc.) across all cluster nodes. When false, only use master nodes
maxCommandRedirections	16	The maximum number of times a command will be redirected due to MOVED or ASK errors
modules		Object defining which Redis Modules to include
scripts		Object defining Lua Scripts to use with this client (see Lua Scripts)

Command Routing

Commands that operate on Redis Keys

Commands such as GET, SET, etc. will be routed by the first key, for instance MGET 1 2 3 will be routed by the key 1.

Server Commands

Admin commands such as MEMORY STATS, FLUSHALL, etc. are not attached to the cluster, and should be executed on a specific node using .getSlot() or .getAllMasters().

"Forwarded Commands"

Some commands (e.g. PUBLISH) are forwarded to other cluster nodes by the Redis server. The client will send these commands to a random node in order to spread the load across the cluster.