A robust, performance-focused and full-featured Redis client for Node.js.

Supports Redis >= 2.6.12 and (Node.js >= 6).

Features

ioredis is a robust, full-featured Redis client that is used in the world's biggest online commerce company Alibaba and many other awesome companies.

0. Full-featured. It supports Cluster, Sentinel, Pipelining and of course Lua scripting & Pub/Sub (with the support of binary messages).
1. High performance.
2. Delightful API. It works with Node callbacks and Native promises.
3. Transformation of command arguments and replies.
4. Transparent key prefixing.
5. Abstraction for Lua scripting, allowing you to define custom commands.
6. Support for binary data.
7. Support for TLS.
8. Support for offline queue and ready checking.
9. Support for ES6 types, such as Map and Set.
10. Support for GEO commands (Redis 3.2 Unstable).
11. Sophisticated error handling strategy.

Links

• API Documentation
• Changelog
• Migrating from node_redis
• Error Handling

Become a Sponsor to Support ioredis's Development

Open source is hard and time-consuming. If you want to invest in ioredis's future you can become a sponsor and make us spend more time on this library's improvements and new features.

Thank you for using ioredis :-)

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---

Quick Start

Install

$ npm install ioredis

Basic Usage

var Redis = require('ioredis');
var redis = new Redis();

redis.set('foo', 'bar');
redis.get('foo', function (err, result) {
  console.log(result);
});

// Or using a promise if the last argument isn't a function
redis.get('foo').then(function (result) {
  console.log(result);
});

// Arguments to commands are flattened, so the following are the same:
redis.sadd('set', 1, 3, 5, 7);
redis.sadd('set', [1, 3, 5, 7]);

// All arguments are passed directly to the redis server:
redis.set('key', 100, 'EX', 10);

See the examples/ folder for more examples.

Connect to Redis

When a new Redis instance is created, a connection to Redis will be created at the same time. You can specify which Redis to connect to by:

new Redis()       // Connect to 127.0.0.1:6379
new Redis(6380)   // 127.0.0.1:6380
new Redis(6379, '192.168.1.1')        // 192.168.1.1:6379
new Redis('/tmp/redis.sock')
new Redis({
  port: 6379,          // Redis port
  host: '127.0.0.1',   // Redis host
  family: 4,           // 4 (IPv4) or 6 (IPv6)
  password: 'auth',
  db: 0
})

You can also specify connection options as a redis:// URL:

// Connect to 127.0.0.1:6380, db 4, using password "authpassword":
new Redis('redis://:authpassword@127.0.0.1:6380/4')

See API Documentation for all available options.

Pub/Sub

Here is a simple example of the API for publish/subscribe. The following program opens two client connections. It subscribes to a channel with one connection and publishes to that channel with the other:

var Redis = require('ioredis');
var redis = new Redis();
var pub = new Redis();
redis.subscribe('news', 'music', function (err, count) {
  // Now we are subscribed to both the 'news' and 'music' channels.
  // `count` represents the number of channels we are currently subscribed to.

  pub.publish('news', 'Hello world!');
  pub.publish('music', 'Hello again!');
});

redis.on('message', function (channel, message) {
  // Receive message Hello world! from channel news
  // Receive message Hello again! from channel music
  console.log('Receive message %s from channel %s', message, channel);
});

// There's also an event called 'messageBuffer', which is the same as 'message' except
// it returns buffers instead of strings.
redis.on('messageBuffer', function (channel, message) {
  // Both `channel` and `message` are buffers.
});

PSUBSCRIBE is also supported in a similar way:

redis.psubscribe('pat?ern', function (err, count) {});
redis.on('pmessage', function (pattern, channel, message) {});
redis.on('pmessageBuffer', function (pattern, channel, message) {});

When a client issues a SUBSCRIBE or PSUBSCRIBE, that connection is put into a "subscriber" mode. At that point, only commands that modify the subscription set are valid. When the subscription set is empty, the connection is put back into regular mode.

If you need to send regular commands to Redis while in subscriber mode, just open another connection.

Handle Binary Data

Arguments can be buffers:

redis.set('foo', Buffer.from('bar'));

And every command has a method that returns a Buffer (by adding a suffix of "Buffer" to the command name). To get a buffer instead of a utf8 string:

redis.getBuffer('foo', function (err, result) {
  // result is a buffer.
});

Pipelining

If you want to send a batch of commands (e.g. > 5), you can use pipelining to queue the commands in memory and then send them to Redis all at once. This way the performance improves by 50%~300% (See benchmark section).

redis.pipeline() creates a Pipeline instance. You can call any Redis commands on it just like the Redis instance. The commands are queued in memory and flushed to Redis by calling the exec method:

var pipeline = redis.pipeline();
pipeline.set('foo', 'bar');
pipeline.del('cc');
pipeline.exec(function (err, results) {
  // `err` is always null, and `results` is an array of responses
  // corresponding to the sequence of queued commands.
  // Each response follows the format `[err, result]`.
});

// You can even chain the commands:
redis.pipeline().set('foo', 'bar').del('cc').exec(function (err, results) {
});

// `exec` also returns a Promise:
var promise = redis.pipeline().set('foo', 'bar').get('foo').exec();
promise.then(function (result) {
  // result === [[null, 'OK'], [null, 'bar']]
});

Each chained command can also have a callback, which will be invoked when the command gets a reply:

redis.pipeline().set('foo', 'bar').get('foo', function (err, result) {
  // result === 'bar'
}).exec(function (err, result) {
  // result[1][1] === 'bar'
});

In addition to adding commands to the pipeline queue individually, you can also pass an array of commands and arguments to the constructor:

redis.pipeline([
  ['set', 'foo', 'bar'],
  ['get', 'foo']
]).exec(function () { /* ... */ });

#length property shows how many commands in the pipeline:

const length = redis.pipeline().set('foo', 'bar').get('foo').length;
// length === 2

Transaction

Most of the time, the transaction commands multi & exec are used together with pipeline. Therefore, when multi is called, a Pipeline instance is created automatically by default, so you can use multi just like pipeline:

redis.multi().set('foo', 'bar').get('foo').exec(function (err, results) {
  // results === [[null, 'OK'], [null, 'bar']]
});

If there's a syntax error in the transaction's command chain (e.g. wrong number of arguments, wrong command name, etc), then none of the commands would be executed, and an error is returned:

redis.multi().set('foo').set('foo', 'new value').exec(function (err, results) {
  // err:
  //  { [ReplyError: EXECABORT Transaction discarded because of previous errors.]
  //    name: 'ReplyError',
  //    message: 'EXECABORT Transaction discarded because of previous errors.',
  //    command: { name: 'exec', args: [] },
  //    previousErrors:
  //     [ { [ReplyError: ERR wrong number of arguments for 'set' command]
  //         name: 'ReplyError',
  //         message: 'ERR wrong number of arguments for \'set\' command',
  //         command: [Object] } ] }
});

In terms of the interface, multi differs from pipeline in that when specifying a callback to each chained command, the queueing state is passed to the callback instead of the result of the command:

redis.multi().set('foo', 'bar', function (err, result) {
  // result === 'QUEUED'
}).exec(/* ... */);

If you want to use transaction without pipeline, pass { pipeline: false } to multi, and every command will be sent to Redis immediately without waiting for an exec invocation:

redis.multi({ pipeline: false });
redis.set('foo', 'bar');
redis.get('foo');
redis.exec(function (err, result) {
  // result === [[null, 'OK'], [null, 'bar']]
});

The constructor of multi also accepts a batch of commands:

redis.multi([
  ['set', 'foo', 'bar'],
  ['get', 'foo']
]).exec(function () { /* ... */ });

Inline transactions are supported by pipeline, which means you can group a subset of commands in the pipeline into a transaction:

redis.pipeline().get('foo').multi().set('foo', 'bar').get('foo').exec().get('foo').exec();

Lua Scripting

ioredis supports all of the scripting commands such as EVAL, EVALSHA and SCRIPT. However, it's tedious to use in real world scenarios since developers have to take care of script caching and to detect when to use EVAL and when to use EVALSHA. ioredis expose a defineCommand method to make scripting much easier to use:

var redis = new Redis();

// This will define a command echo:
redis.defineCommand('echo', {
  numberOfKeys: 2,
  lua: 'return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}'
});

// Now `echo` can be used just like any other ordinary command,
// and ioredis will try to use `EVALSHA` internally when possible for better performance.
redis.echo('k1', 'k2', 'a1', 'a2', function (err, result) {
  // result === ['k1', 'k2', 'a1', 'a2']
});

// `echoBuffer` is also defined automatically to return buffers instead of strings:
redis.echoBuffer('k1', 'k2', 'a1', 'a2', function (err, result) {
  // result[0] equals to Buffer.from('k1');
});

// And of course it works with pipeline:
redis.pipeline().set('foo', 'bar').echo('k1', 'k2', 'a1', 'a2').exec();

If the number of keys can't be determined when defining a command, you can omit the numberOfKeys property and pass the number of keys as the first argument when you call the command:

redis.defineCommand('echoDynamicKeyNumber', {
  lua: 'return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}'
});

// Now you have to pass the number of keys as the first argument every time
// you invoke the `echoDynamicKeyNumber` command:
redis.echoDynamicKeyNumber(2, 'k1', 'k2', 'a1', 'a2', function (err, result) {
  // result === ['k1', 'k2', 'a1', 'a2']
});

Transparent Key Prefixing

This feature allows you to specify a string that will automatically be prepended to all the keys in a command, which makes it easier to manage your key namespaces.

Warning This feature won't apply to commands like KEYS and SCAN that take patterns rather than actual keys(#239), and this feature also won't apply to the replies of commands even they are key names (#325).

var fooRedis = new Redis({ keyPrefix: 'foo:' });
fooRedis.set('bar', 'baz');  // Actually sends SET foo:bar baz

fooRedis.defineCommand('echo', {
  numberOfKeys: 2,
  lua: 'return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}'
});

// Works well with pipelining/transaction
fooRedis.pipeline()
  // Sends SORT foo:list BY foo:weight_*->fieldname
  .sort('list', 'BY', 'weight_*->fieldname')
  // Supports custom commands
  // Sends EVALSHA xxx foo:k1 foo:k2 a1 a2
  .echo('k1', 'k2', 'a1', 'a2')
  .exec()

Transforming Arguments & Replies

Most Redis commands take one or more Strings as arguments, and replies are sent back as a single String or an Array of Strings. However, sometimes you may want something different. For instance, it would be more convenient if the HGETALL command returns a hash (e.g. { key: val1, key2: v2 }) rather than an array of key values (e.g. [key1, val1, key2, val2]).

ioredis has a flexible system for transforming arguments and replies. There are two types of transformers, argument transformer and reply transformer:

var Redis = require('ioredis');

// Here's the built-in argument transformer converting
// hmset('key', { k1: 'v1', k2: 'v2' })
// or
// hmset('key', new Map([['k1', 'v1'], ['k2', 'v2']]))
// into
// hmset('key', 'k1', 'v1', 'k2', 'v2')
Redis.Command.setArgumentTransformer('hmset', function (args) {
  if (args.length === 2) {
    if (typeof Map !== 'undefined' && args[1] instanceof Map) {
      // utils is a internal module of ioredis
      return [args[0]].concat(utils.convertMapToArray(args[1]));
    }
    if ( typeof args[1] === 'object' && args[1] !== null) {
      return [args[0]].concat(utils.convertObjectToArray(args[1]));
    }
  }
  return args;
});

// Here's the built-in reply transformer converting the HGETALL reply
// ['k1', 'v1', 'k2', 'v2']
// into
// { k1: 'v1', 'k2': 'v2' }
Redis.Command.setReplyTransformer('hgetall', function (result) {
  if (Array.isArray(result)) {
    var obj = {};
    for (var i = 0; i < result.length; i += 2) {
      obj[result[i]] = result[i + 1];
    }
    return obj;
  }
  return result;
});

There are three built-in transformers, two argument transformers for hmset & mset and a reply transformer for hgetall. Transformers for hmset and hgetall were mentioned above, and the transformer for mset is similar to the one for hmset:

redis.mset({ k1: 'v1', k2: 'v2' });
redis.get('k1', function (err, result) {
  // result === 'v1';
});

redis.mset(new Map([['k3', 'v3'], ['k4', 'v4']]));
redis.get('k3', function (err, result) {
  // result === 'v3';
});

Another useful example of a reply transformer is one that changes hgetall to return array of arrays instead of objects which avoids a unwanted conversation of hash keys to strings when dealing with binary hash keys:

Redis.Command.setReplyTransformer('hgetall', function (result) {
  var arr = [];
  for (var i = 0; i < result.length; i += 2) {
    arr.push([result[i], result[i + 1]]);
  }
  return arr;
});
redis.hset('h1', Buffer.from([0x01]), Buffer.from([0x02]));
redis.hset('h1', Buffer.from([0x03]), Buffer.from([0x04]));
redis.hgetallBuffer('h1', function (err, result) {
  // result === [ [ <Buffer 01>, <Buffer 02> ], [ <Buffer 03>, <Buffer 04> ] ];
});

Monitor

Redis supports the MONITOR command, which lets you see all commands received by the Redis server across all client connections, including from other client libraries and other computers.

The monitor method returns a monitor instance. After you send the MONITOR command, no other commands are valid on that connection. ioredis will emit a monitor event for every new monitor message that comes across. The callback for the monitor event takes a timestamp from the Redis server and an array of command arguments.

Here is a simple example:

redis.monitor(function (err, monitor) {
  monitor.on('monitor', function (time, args, source, database) {
  });
});

Streamify Scanning

Redis 2.8 added the SCAN command to incrementally iterate through the keys in the database. It's different from KEYS in that SCAN only returns a small number of elements each call, so it can be used in production without the downside of blocking the server for a long time. However, it requires recording the cursor on the client side each time the SCAN command is called in order to iterate through all the keys correctly. Since it's a relatively common use case, ioredis provides a streaming interface for the SCAN command to make things much easier. A readable stream can be created by calling scanStream:

var redis = new Redis();
// Create a readable stream (object mode)
var stream = redis.scanStream();
stream.on('data', function (resultKeys) {
  // `resultKeys` is an array of strings representing key names.
  // Note that resultKeys may contain 0 keys, and that it will sometimes
  // contain duplicates due to SCAN's implementation in Redis.
  for (var i = 0; i < resultKeys.length; i++) {
    console.log(resultKeys[i]);
  }
});
stream.on('end', function () {
  console.log('all keys have been visited');
});

scanStream accepts an option, with which you can specify the MATCH pattern and the COUNT argument:

var stream = redis.scanStream({
  // only returns keys following the pattern of `user:*`
  match: 'user:*',
  // returns approximately 100 elements per call
  count: 100
});

Just like other commands, scanStream has a binary version scanBufferStream, which returns an array of buffers. It's useful when the key names are not utf8 strings.

There are also hscanStream, zscanStream and sscanStream to iterate through elements in a hash, zset and set. The interface of each is similar to scanStream except the first argument is the key name:

var stream = redis.hscanStream('myhash', {
  match: 'age:??'
});

You can learn more from the Redis documentation.

Useful Tips It's pretty common that doing an async task in the data handler. We'd like the scanning process to be paused until the async task to be finished. Stream#pause() and Stream.resume() do the trick. For example if we want to migrate data in Redis to MySQL:

var stream = redis.scanStream();
stream.on('data', function (resultKeys) {
  // Pause the stream from scanning more keys until we've migrated the current keys.
  stream.pause();

  Promise.all(resultKeys.map(migrateKeyToMySQL)).then(() => {
    // Resume the stream here.
    stream.resume();
  });
});

stream.on('end', function () {
  console.log('done migration');
});

Auto-reconnect

By default, ioredis will try to reconnect when the connection to Redis is lost except when the connection is closed manually by redis.disconnect() or redis.quit().

It's very flexible to control how long to wait to reconnect after disconnection using the retryStrategy option:

var redis = new Redis({
  // This is the default value of `retryStrategy`
  retryStrategy: function (times) {
    var delay = Math.min(times * 50, 2000);
    return delay;
  }
});

retryStrategy is a function that will be called when the connection is lost. The argument times means this is the nth reconnection being made and the return value represents how long (in ms) to wait to reconnect. When the return value isn't a number, ioredis will stop trying to reconnect, and the connection will be lost forever if the user doesn't call redis.connect() manually.

When reconnected, the client will auto subscribe to channels that the previous connection subscribed to. This behavior can be disabled by setting the autoResubscribe option to false.

And if the previous connection has some unfulfilled commands (most likely blocking commands such as brpop and blpop), the client will resend them when reconnected. This behavior can be disabled by setting the autoResendUnfulfilledCommands option to false.

By default, all pending commands will be flushed with an error every 20 retry attempts. That makes sure commands won't wait forever when the connection is down. You can change this behavior by setting maxRetriesPerRequest:

var redis = new Redis({
  maxRetriesPerRequest: 1
});

Set maxRetriesPerRequest to null to disable this behavior, and every command will wait forever until the connection is alive again (which is the default behavior before ioredis v4).

Reconnect on error

Besides auto-reconnect when the connection is closed, ioredis supports reconnecting on the specified errors by the reconnectOnError option. Here's an example that will reconnect when receiving READONLY error:

var redis = new Redis({
  reconnectOnError: function (err) {
    var targetError = 'READONLY';
    if (err.message.slice(0, targetError.length) === targetError) {
      // Only reconnect when the error starts with "READONLY"
      return true; // or `return 1;`
    }
  }
});

This feature is useful when using Amazon ElastiCache. Once failover happens, Amazon ElastiCache will switch the master we currently connected with to a slave, leading to the following writes fails with the error READONLY. Using reconnectOnError, we can force the connection to reconnect on this error in order to connect to the new master.

Furthermore, if the reconnectOnError returns 2, ioredis will resend the failed command after reconnecting.

Connection Events

The Redis instance will emit some events about the state of the connection to the Redis server.

Event	Description
connect	emits when a connection is established to the Redis server.
ready	If enableReadyCheck is true, client will emit ready when the server reports that it is ready to receive commands (e.g. finish loading data from disk). Otherwise, ready will be emitted immediately right after the connect event.
error	emits when an error occurs while connecting. However, ioredis emits all error events silently (only emits when there's at least one listener) so that your application won't crash if you're not listening to the error event.
close	emits when an established Redis server connection has closed.
reconnecting	emits after close when a reconnection will be made. The argument of the event is the time (in ms) before reconnecting.
end	emits after close when no more reconnections will be made, or the connection is failed to establish.

You can also check out the Redis#status property to get the current connection status.

Besides the above connection events, there are several other custom events:

Event	Description
select	emits when the database changed. The argument is the new db number.

Offline Queue

When a command can't be processed by Redis (being sent before the ready event), by default, it's added to the offline queue and will be executed when it can be processed. You can disable this feature by setting the enableOfflineQueue option to false:

var redis = new Redis({ enableOfflineQueue: false });

TLS Options

Redis doesn't support TLS natively, however if the redis server you want to connect to is hosted behind a TLS proxy (e.g. stunnel) or is offered by a PaaS service that supports TLS connection (e.g. Redis Labs), you can set the tls option:

var redis = new Redis({
  host: 'localhost',
  tls: {
    // Refer to `tls.connect()` section in
    // https://nodejs.org/api/tls.html
    // for all supported options
    ca: fs.readFileSync('cert.pem')
  }
});

---

Sentinel

ioredis supports Sentinel out of the box. It works transparently as all features that work when you connect to a single node also work when you connect to a sentinel group. Make sure to run Redis >= 2.8.12 if you want to use this feature. Sentinels have a default port of 26379.

To connect using Sentinel, use:

var redis = new Redis({
  sentinels: [{ host: 'localhost', port: 26379 }, { host: 'localhost', port: 26380 }],
  name: 'mymaster'
});

redis.set('foo', 'bar');

The arguments passed to the constructor are different from the ones you use to connect to a single node, where:

• name identifies a group of Redis instances composed of a master and one or more slaves (mymaster in the example);
• sentinels are a list of sentinels to connect to. The list does not need to enumerate all your sentinel instances, but a few so that if one is down the client will try the next one.
• role (optional) with a value of slave will return a random slave from the Sentinel group.
• preferredSlaves (optional) can be used to prefer a particular slave or set of slaves based on priority. It accepts a function or array.

ioredis guarantees that the node you connected to is always a master even after a failover. When a failover happens, instead of trying to reconnect to the failed node (which will be demoted to slave when it's available again), ioredis will ask sentinels for the new master node and connect to it. All commands sent during the failover are queued and will be executed when the new connection is established so that none of the commands will be lost.

It's possible to connect to a slave instead of a master by specifying the option role with the value of slave and ioredis will try to connect to a random slave of the specified master, with the guarantee that the connected node is always a slave. If the current node is promoted to master due to a failover, ioredis will disconnect from it and ask the sentinels for another slave node to connect to.

If you specify the option preferredSlaves along with role: 'slave' ioredis will attempt to use this value when selecting the slave from the pool of available slaves. The value of preferredSlaves should either be a function that accepts an array of avaiable slaves and returns a single result, or an array of slave values priorities by the lowest prio value first with a default value of 1.

// available slaves format
var availableSlaves = [{ ip: '127.0.0.1', port: '31231', flags: 'slave' }];

// preferredSlaves array format
var preferredSlaves = [
  { ip: '127.0.0.1', port: '31231', prio: 1 },
  { ip: '127.0.0.1', port: '31232', prio: 2 }
];

// preferredSlaves function format
preferredSlaves = function(availableSlaves) {
  for (var i = 0; i < availableSlaves.length; i++) {
    var slave = availableSlaves[i];
    if (slave.ip === '127.0.0.1') {
      if (slave.port === '31234') {
        return slave;
      }
    }
  }
  // if no preferred slaves are available a random one is used
  return false;
};

var redis = new Redis({
  sentinels: [{ host: '127.0.0.1', port: 26379 }, { host: '127.0.0.1', port: 26380 }],
  name: 'mymaster',
  role: 'slave',
  preferredSlaves: preferredSlaves
});

Besides the retryStrategy option, there's also a sentinelRetryStrategy in Sentinel mode which will be invoked when all the sentinel nodes are unreachable during connecting. If sentinelRetryStrategy returns a valid delay time, ioredis will try to reconnect from scratch. The default value of sentinelRetryStrategy is:

function (times) {
  var delay = Math.min(times * 10, 1000);
  return delay;
}

Cluster

Redis Cluster provides a way to run a Redis installation where data is automatically sharded across multiple Redis nodes. You can connect to a Redis Cluster like this:

var Redis = require('ioredis');

var cluster = new Redis.Cluster([{
  port: 6380,
  host: '127.0.0.1'
}, {
  port: 6381,
  host: '127.0.0.1'
}]);

cluster.set('foo', 'bar');
cluster.get('foo', function (err, res) {
  // res === 'bar'
});

Cluster constructor accepts two arguments, where:

0. The first argument is a list of nodes of the cluster you want to connect to. Just like Sentinel, the list does not need to enumerate all your cluster nodes, but a few so that if one is unreachable the client will try the next one, and the client will discover other nodes automatically when at least one node is connected.

1. The second argument is the options, where:

   • clusterRetryStrategy: When none of the startup nodes are reachable, clusterRetryStrategy will be invoked. When a number is returned, ioredis will try to reconnect to the startup nodes from scratch after the specified delay (in ms). Otherwise, an error of "None of startup nodes is available" will be returned. The default value of this option is:

     function (times) {
       var delay = Math.min(100 + times * 2, 2000);
       return delay;
     }

     It's possible to modify the startupNodes property in order to switch to another set of nodes here:

     function (times) {
       this.startupNodes = [{ port: 6790, host: '127.0.0.1' }];
       return Math.min(100 + times * 2, 2000);
     }

   • enableOfflineQueue: Similar to the enableOfflineQueue option of Redis class.

   • enableReadyCheck: When enabled, "ready" event will only be emitted when CLUSTER INFO command reporting the cluster is ready for handling commands. Otherwise, it will be emitted immediately after "connect" is emitted.

   • scaleReads: Config where to send the read queries. See below for more details.

   • maxRedirections: When a cluster related error (e.g. MOVED, ASK and CLUSTERDOWN etc.) is received, the client will redirect the command to another node. This option limits the max redirections allowed when sending a command. The default value is 16.

   • retryDelayOnFailover: If the target node is disconnected when sending a command, ioredis will retry after the specified delay. The default value is 100. You should make sure retryDelayOnFailover * maxRedirections > cluster-node-timeout to insure that no command will fail during a failover.

   • retryDelayOnClusterDown: When a cluster is down, all commands will be rejected with the error of CLUSTERDOWN. If this option is a number (by default, it is 100), the client will resend the commands after the specified time (in ms).

   • retryDelayOnTryAgain: If this option is a number (by default, it is 100), the client will resend the commands rejected with TRYAGAIN error after the specified time (in ms).

   • redisOptions: Default options passed to the constructor of Redis when connecting to a node.

   • slotsRefreshTimeout: Milliseconds before a timeout occurs while refreshing slots from the cluster (default 1000)

   • slotsRefreshInterval: Milliseconds between every automatic slots refresh (default 5000)

Read-write splitting

A typical redis cluster contains three or more masters and several slaves for each master. It's possible to scale out redis cluster by sending read queries to slaves and write queries to masters by setting the scaleReads option.

scaleReads is "master" by default, which means ioredis will never send any queries to slaves. There are other three available options:

1. "all": Send write queries to masters and read queries to masters or slaves randomly.
2. "slave": Send write queries to masters and read queries to slaves.
3. a custom function(nodes, command): node: Will choose the custom function to select to which node to send read queries (write queries keep being sent to master). The first node in nodes is always the master serving the relevant slots. If the function returns an array of nodes, a random node of that list will be selected.

For example:

var cluster = new Redis.Cluster([/* nodes */], {
  scaleReads: 'slave'
});
cluster.set('foo', 'bar'); // This query will be sent to one of the masters.
cluster.get('foo', function (err, res) {
  // This query will be sent to one of the slaves.
});

NB In the code snippet above, the res may not be equal to "bar" because of the lag of replication between the master and slaves.

Running commands to multiple nodes

Every command will be sent to exactly one node. For commands containing keys, (e.g. GET, SET and HGETALL), ioredis sends them to the node that serving the keys, and for other commands not containing keys, (e.g. INFO, KEYS and FLUSHDB), ioredis sends them to a random node.

Sometimes you may want to send a command to multiple nodes (masters or slaves) of the cluster, you can get the nodes via Cluster#nodes() method.

Cluster#nodes() accepts a parameter role, which can be "master", "slave" and "all" (default), and returns an array of Redis instance. For example:

// Send `FLUSHDB` command to all slaves:
var slaves = cluster.nodes('slave');
Promise.all(slaves.map(function (node) {
  return node.flushdb();
}));

// Get keys of all the masters:
var masters = cluster.nodes('master');
Promise.all(masters.map(function (node) {
  return node.keys();
})).then(function (keys) {
  // keys: [['key1', 'key2'], ['key3', 'key4']]
});

Transaction and pipeline in Cluster mode

Almost all features that are supported by Redis are also supported by Redis.Cluster, e.g. custom commands, transaction and pipeline. However there are some differences when using transaction and pipeline in Cluster mode:

0. All keys in a pipeline should belong to the same slot since ioredis sends all commands in a pipeline to the same node.
1. You can't use multi without pipeline (aka cluster.multi({ pipeline: false })). This is because when you call cluster.multi({ pipeline: false }), ioredis doesn't know which node the multi command should be sent to.
2. Chaining custom commands in the pipeline is not supported in Cluster mode.

When any commands in a pipeline receives a MOVED or ASK error, ioredis will resend the whole pipeline to the specified node automatically if all of the following conditions are satisfied:

0. All errors received in the pipeline are the same. For example, we won't resend the pipeline if we got two MOVED errors pointing to different nodes.
1. All commands executed successfully are readonly commands. This makes sure that resending the pipeline won't have side effects.

Pub/Sub

Pub/Sub in cluster mode works exactly as the same as in standalone mode. Internally, when a node of the cluster receives a message, it will broadcast the message to the other nodes. ioredis makes sure that each message will only be received once by strictly subscribing one node at the same time.

var nodes = [/* nodes */];
var pub = new Redis.Cluster(nodes);
var sub = new Redis.Cluster(nodes);
sub.on('message', function (channel, message) {
  console.log(channel, message);
});

sub.subscribe('news', function () {
  pub.publish('news', 'highlights');
});

Events

Event	Description
connect	emits when a connection is established to the Redis server.
ready	emits when CLUSTER INFO reporting the cluster is able to receive commands (if enableReadyCheck is true) or immediately after connect event (if enableReadyCheck is false).
error	emits when an error occurs while connecting with a property of lastNodeError representing the last node error received. This event is emitted silently (only emitting if there's at least one listener).
close	emits when an established Redis server connection has closed.
reconnecting	emits after close when a reconnection will be made. The argument of the event is the time (in ms) before reconnecting.
end	emits after close when no more reconnections will be made.
+node	emits when a new node is connected.
-node	emits when a node is disconnected.
node error	emits when an error occurs when connecting to a node

Password

Setting the password option to access password-proctected clusters:

var Redis = require('ioredis');
var cluster = new Redis.Cluster(nodes, {
  redisOptions: {
    password: 'your-cluster-password'
  }
});

If some of nodes in the cluster using a different password, you should specify them in the first parameter:

var Redis = require('ioredis');
var cluster = new Redis.Cluster([
  // Use password "password-for-30001" for 30001
  { port: 30001, password: 'password-for-30001'},
  // Don't use password when accessing 30002
  { port: 30002, password: null }
  // Other nodes will use "fallback-password"
], {
  redisOptions: {
    password: 'fallback-password'
  }
});

---

Error Handling

All the errors returned by the Redis server are instances of ReplyError, which can be accessed via Redis:

var Redis = require('ioredis');
var redis = new Redis();
// This command causes a reply error since the SET command requires two arguments.
redis.set('foo', function (err) {
  err instanceof Redis.ReplyError
});

This is the error stack of the ReplyError:

ReplyError: ERR wrong number of arguments for 'set' command
    at ReplyParser._parseResult (/app/node_modules/ioredis/lib/parsers/javascript.js:60:14)
    at ReplyParser.execute (/app/node_modules/ioredis/lib/parsers/javascript.js:178:20)
    at Socket.<anonymous> (/app/node_modules/ioredis/lib/redis/event_handler.js:99:22)
    at Socket.emit (events.js:97:17)
    at readableAddChunk (_stream_readable.js:143:16)
    at Socket.Readable.push (_stream_readable.js:106:10)
    at TCP.onread (net.js:509:20)

By default, the error stack doesn't make any sense because the whole stack happens in the ioredis module itself, not in your code. So it's not easy to find out where the error happens in your code. ioredis provides an option showFriendlyErrorStack to solve the problem. When you enable showFriendlyErrorStack, ioredis will optimize the error stack for you:

var Redis = require('ioredis');
var redis = new Redis({ showFriendlyErrorStack: true });
redis.set('foo');

And the output will be:

ReplyError: ERR wrong number of arguments for 'set' command
    at Object.<anonymous> (/app/index.js:3:7)
    at Module._compile (module.js:446:26)
    at Object.Module._extensions..js (module.js:464:10)
    at Module.load (module.js:341:32)
    at Function.Module._load (module.js:296:12)
    at Function.Module.runMain (module.js:487:10)
    at startup (node.js:111:16)
    at node.js:799:3

This time the stack tells you that the error happens on the third line in your code. Pretty sweet! However, it would decrease the performance significantly to optimize the error stack. So by default, this option is disabled and can only be used for debugging purposes. You shouldn't use this feature in a production environment.

Plugging in your own Promises Library

If you're an advanced user, you may want to plug in your own promise library like bluebird. Just set Redis.Promise to your favorite ES6-style promise constructor and ioredis will use it.

const Redis = require('ioredis')
Redis.Promise = require('bluebird')

const redis = new Redis()

// Use bluebird
assert.equal(redis.get().constructor, require('bluebird'))

// You can change the Promise implementation at any time:
Redis.Promise = global.Promise
assert.equal(redis.get().constructor, global.Promise)

Running tests

Start a Redis server on 127.0.0.1:6379, and then:

$ npm test

FLUSH ALL will be invoked after each test, so make sure there's no valuable data in it before running tests.

If your testing environment does not let you spin up a Redis server ioredis-mock is a drop-in replacement you can use in your tests. It aims to behave identically to ioredis connected to a Redis server so that your integration tests is easier to write and of better quality.

Debug

You can set the DEBUG env to ioredis:* to print debug info:

$ DEBUG=ioredis:* node app.js

Consolidation: It's time for celebration

Right now there are two great redis clients around and both have some advantages above each other. We speak about node_redis and ioredis. So after talking to each other about how we could improve in working together we (that is @BridgeAR and @luin) decided to work towards a single library on the long run. But step by step.

First of all, we want to split small parts of our libraries into others so that we're both able to use the same code. Those libraries are going to be maintained under the NodeRedis organization. This is going to reduce the maintance overhead, allows others to use the very same code, if they need it and it's way easier for others to contribute to both libraries.

We're very happy about this step towards working together as we both want to give you the best redis experience possible.

If you want to join our cause by help maintaining something, please don't hesitate to contact either one of us.

Join in!

I'm happy to receive bug reports, fixes, documentation enhancements, and any other improvements.

And since I'm not a native English speaker, if you find any grammar mistakes in the documentation, please also let me know. :)

Contributors

This project exists thanks to all the people who contribute:

License

MIT