How to integrate redis-sentinel-client and socket.io on node.js?

Question

How can I integrate socket.io, and a master-slave Redis configuration with automatic failover?

Answer 1

I've used the following configuration:

1. Create a master redis instance.
2. Create a trio of redis-sentinel-client processes and point them to the master redis instance. You only need to reference one of them in the configuration below, because the client will fill in the rest.
3. Create a slave redis instance, and point it to the master.

Use the following to configure your RedisStore with socket.io:

var redisOptions = {
  host: 'localhost', // || redisSentinelHost,
  port: 26379, // Default sentinel port.
  masterName: 'mymaster'
};

var RedisStore = require('socket.io/lib/stores/redis'),
  // The redis-sentinel-client requires a forked redis client
  // that is available here:
  redis = require('redis-sentinel-client/node_modules/redis'),

  // A sentinel client is required to back each of the redis
  // clients below. The sentinel clients handle the fail-overs.
  sentinel = require('redis-sentinel-client'),
  redisPubSentinel = sentinel.createClient(redisOptions),
  redisSubSentinel = sentinel.createClient(redisOptions),
  redisClientSentinel = sentinel.createClient(redisOptions),
  redisPub = redisClientSentinel.getMaster(),
  redisSub = redisSubSentinel.getMaster(),
  redisClient = redisPubSentinel.getMaster();

// We must be robust to connection errors in order to allow
// for a reconnect. We therefore prevent redis client errors
// from stopping the application.
[ redisPubSentinel,
  redisSubSentinel,
  redisClientSentinel,
  redisPub,
  redisSub,
  redisClient ].forEach(function(c) {
  c.on('error', function(err) {
    logger.log(err);
  });
});

io.set('store', new RedisStore({
  redis: redis,
  redisPub: redisPub,
  redisSub: redisSub,
  redisClient: redisClient
  })
);