redis

What is redis?

The npm package 'redis' is a Node.js client for Redis, a fast, open-source, in-memory key-value data store for use as a database, cache, message broker, and queue. The package allows Node.js applications to interact with Redis servers using an asynchronous, event-driven model.

What are redis's main functionalities?

Connecting to Redis

This code sample demonstrates how to connect to a Redis server using the redis npm package. It requires the package, creates a client, and listens for the 'connect' event to confirm the connection.

const redis = require('redis');
const client = redis.createClient();
client.on('connect', function() {
  console.log('Connected to Redis');
});

Setting and Getting Data

This code sample shows how to set a key-value pair in Redis and then retrieve the value associated with a key. The 'redis.print' callback is used to output the result of the 'set' operation.

client.set('key', 'value', redis.print);
client.get('key', function(err, reply) {
  console.log(reply); // prints 'value'
});

Working with Lists

This code sample illustrates how to work with Redis lists by pushing values to the end of a list and then retrieving the entire list.

client.rpush(['list', 'value1', 'value2'], redis.print);
client.lrange('list', 0, -1, function(err, reply) {
  console.log(reply); // prints ['value1', 'value2']
});

Publish/Subscribe

This code sample demonstrates the publish/subscribe capabilities of Redis. It creates a subscriber client that listens for messages on a channel and a publisher client that publishes a message to that channel.

const subscriber = redis.createClient();
const publisher = redis.createClient();
subscriber.on('message', function(channel, message) {
  console.log('Message: ' + message + ' on channel: ' + channel);
});
subscriber.subscribe('notification');
publisher.publish('notification', 'Hello, World!');

Transactions

This code sample shows how to use Redis transactions to execute multiple commands atomically using the 'multi' and 'exec' methods.

client.multi()
  .set('key', 'value')
  .incr('counter')
  .exec(function(err, replies) {
    console.log(replies); // prints results of all commands
  });

Other packages similar to redis

ioredis

ioredis is a robust, performance-focused, and full-featured Redis client for Node.js. It supports Redis Cluster, Sentinel, pipelining, Lua scripting, and more. Compared to the 'redis' package, ioredis offers a more modern interface with Promises support and better performance for certain operations.

node-redis

node-redis is another Redis client for Node.js that is designed to be easy to use. It may not have as many features as 'redis' or 'ioredis', but it provides a straightforward way to interact with Redis servers for simple use cases.

redis-mock

redis-mock is a library that simulates a Redis server for testing purposes. It implements most of the Redis commands and can be used as a drop-in replacement for the 'redis' package during testing, without the need for an actual Redis server.

README

Node-Redis

node-redis is a modern, high performance Redis client for Node.js.

Packages

Name	Description
redis
@redis/client
@redis/bloom	Redis Bloom commands
@redis/graph	Redis Graph commands
@redis/json	Redis JSON commands
@redis/search	Redis Search commands
@redis/time-series	Redis Time-Series commands

:warning: In version 4.1.0 we moved our subpackages from @node-redis to @redis. If you're just using npm install redis, you don't need to do anything—it'll upgrade automatically. If you're using the subpackages directly, you'll need to point to the new scope (e.g. @redis/client instead of @node-redis/client).

Installation

npm install redis

:warning: The new interface is clean and cool, but if you have an existing codebase, you'll want to read the migration guide.

Looking for a high-level library to handle object mapping? See redis-om-node!

Usage

Basic Example

import { createClient } from 'redis';

const client = createClient();

client.on('error', (err) => console.log('Redis Client Error', err));

await client.connect();

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

The above code connects to localhost on port 6379. To connect to a different host or port, use a connection string in the format redis[s]://[[username][:password]@][host][:port][/db-number]:

createClient({
  url: 'redis://alice:[e-mail]:6380'
});

You can also use discrete parameters, UNIX sockets, and even TLS to connect. Details can be found in the client configuration guide.

Redis Commands

There is built-in support for all of the out-of-the-box Redis commands. They are exposed using the raw Redis command names (HSET, HGETALL, etc.) and a friendlier camel-cased version (hSet, hGetAll, etc.):

// raw Redis commands
await client.HSET('key', 'field', 'value');
await client.HGETALL('key');

// friendly JavaScript commands
await client.hSet('key', 'field', 'value');
await client.hGetAll('key');

Modifiers to commands are specified using a JavaScript object:

await client.set('key', 'value', {
  EX: 10,
  NX: true
});

Replies will be transformed into useful data structures:

await client.hGetAll('key'); // { field1: 'value1', field2: 'value2' }
await client.hVals('key'); // ['value1', 'value2']

Buffers are supported as well:

await client.hSet('key', 'field', Buffer.from('value')); // 'OK'
await client.hGetAll(
  commandOptions({ returnBuffers: true }),
  'key'
); // { field: <Buffer 76 61 6c 75 65> }

Unsupported Redis Commands

If you want to run commands and/or use arguments that Node Redis doesn't know about (yet!) use .sendCommand():

await client.sendCommand(['SET', 'key', 'value', 'NX']); // 'OK'

await client.sendCommand(['HGETALL', 'key']); // ['key1', 'field1', 'key2', 'field2']

Transactions (Multi/Exec)

Start a transaction by calling .multi(), then chaining your commands. When you're done, call .exec() and you'll get an array back with your results:

await client.set('another-key', 'another-value');

const [setKeyReply, otherKeyValue] = await client
  .multi()
  .set('key', 'value')
  .get('another-key')
  .exec(); // ['OK', 'another-value']

You can also watch keys by calling .watch(). Your transaction will abort if any of the watched keys change.

To dig deeper into transactions, check out the Isolated Execution Guide.

Blocking Commands

Any command can be run on a new connection by specifying the isolated option. The newly created connection is closed when the command's Promise is fulfilled.

This pattern works especially well for blocking commands—such as BLPOP and BLMOVE:

import { commandOptions } from 'redis';

const blPopPromise = client.blPop(
  commandOptions({ isolated: true }),
  'key',
  0
);

await client.lPush('key', ['1', '2']);

await blPopPromise; // '2'

To learn more about isolated execution, check out the guide.

Pub/Sub

Subscribing to a channel requires a dedicated stand-alone connection. You can easily get one by .duplicate()ing an existing Redis connection.

const subscriber = client.duplicate();

await subscriber.connect();

Once you have one, simply subscribe and unsubscribe as needed:

await subscriber.subscribe('channel', (message) => {
  console.log(message); // 'message'
});

await subscriber.pSubscribe('channe*', (message, channel) => {
  console.log(message, channel); // 'message', 'channel'
});

await subscriber.unsubscribe('channel');

await subscriber.pUnsubscribe('channe*');

Publish a message on a channel:

await publisher.publish('channel', 'message');

There is support for buffers as well:

await subscriber.subscribe('channel', (message) => {
  console.log(message); // <Buffer 6d 65 73 73 61 67 65>
}, true);

await subscriber.pSubscribe('channe*', (message, channel) => {
  console.log(message, channel); // <Buffer 6d 65 73 73 61 67 65>, <Buffer 63 68 61 6e 6e 65 6c>
}, true);

Scan Iterator

SCAN results can be looped over using async iterators:

for await (const key of client.scanIterator()) {
  // use the key!
  await client.get(key);
}

This works with HSCAN, SSCAN, and ZSCAN too:

for await (const { field, value } of client.hScanIterator('hash')) {}
for await (const member of client.sScanIterator('set')) {}
for await (const { score, value } of client.zScanIterator('sorted-set')) {}

You can override the default options by providing a configuration object:

client.scanIterator({
  TYPE: 'string', // `SCAN` only
  MATCH: 'patter*',
  COUNT: 100
});

Programmability

Redis provides a programming interface allowing code execution on the redis server.

Functions

The following example retrieves a key in redis, returning the value of the key, incremented by an integer. For example, if your key foo has the value 17 and we run add('foo', 25), it returns the answer to Life, the Universe and Everything.

#!lua name=library

redis.register_function {
  function_name = 'add',
  callback = function(keys, args) return redis.call('GET', keys[1]) + args[1] end,
  flags = { 'no-writes' }
}

Here is the same example, but in a format that can be pasted into the redis-cli.

FUNCTION LOAD "#!lua name=library\nredis.register_function{function_name=\"add\", callback=function(keys, args) return redis.call('GET', keys[1])+args[1] end, flags={\"no-writes\"}}"

Load the prior redis function on the redis server before running the example below.

import { createClient } from 'redis';

const client = createClient({
  functions: {
    library: {
      add: {
        NUMBER_OF_KEYS: 1,
        transformArguments(key: string, toAdd: number): Array<string> {
          return [key, toAdd.toString()];
        },
        transformReply(reply: number): number {
          return reply;
        }
      }
    }
  }
});

await client.connect();

await client.set('key', '1');
await client.library.add('key', 2); // 3

Lua Scripts

The following is an end-to-end example of the prior concept.

import { createClient, defineScript } from 'redis';

const client = createClient({
  scripts: {
    add: defineScript({
      NUMBER_OF_KEYS: 1,
      SCRIPT:
        'return redis.call("GET", KEYS[1]) + ARGV[1];',
      transformArguments(key: string, toAdd: number): Array<string> {
        return [key, toAdd.toString()];
      },
      transformReply(reply: number): number {
        return reply;
      }
    })
  }
});

await client.connect();

await client.set('key', '1');
await client.add('key', 2); // 3

Disconnecting

There are two functions that disconnect a client from the Redis server. In most scenarios you should use .quit() to ensure that pending commands are sent to Redis before closing a connection.

.QUIT()/.quit()

Gracefully close a client's connection to Redis, by sending the QUIT command to the server. Before quitting, the client executes any remaining commands in its queue, and will receive replies from Redis for each of them.

const [ping, get, quit] = await Promise.all([
  client.ping(),
  client.get('key'),
  client.quit()
]); // ['PONG', null, 'OK']

try {
  await client.get('key');
} catch (err) {
  // ClosedClient Error
}

.disconnect()

Forcibly close a client's connection to Redis immediately. Calling disconnect will not send further pending commands to the Redis server, or wait for or parse outstanding responses.

await client.disconnect();

Auto-Pipelining

Node Redis will automatically pipeline requests that are made during the same "tick".

client.set('Tm9kZSBSZWRpcw==', 'users:1');
client.sAdd('users:1:tokens', 'Tm9kZSBSZWRpcw==');

Of course, if you don't do something with your Promises you're certain to get unhandled Promise exceptions. To take advantage of auto-pipelining and handle your Promises, use Promise.all().

await Promise.all([
  client.set('Tm9kZSBSZWRpcw==', 'users:1'),
  client.sAdd('users:1:tokens', 'Tm9kZSBSZWRpcw==')
]);

Clustering

Check out the Clustering Guide when using Node Redis to connect to a Redis Cluster.

Events

The Node Redis client class is an Nodejs EventEmitter and it emits an event each time the network status changes:

Event name	Scenes	Arguments to be passed to the listener
connect	The client is initiating a connection to the server.	No argument
ready	The client successfully initiated the connection to the server.	No argument
end	The client disconnected the connection to the server via .quit() or .disconnect().	No argument
error	When a network error has occurred, such as unable to connect to the server or the connection closed unexpectedly.	1 argument: The error object, such as SocketClosedUnexpectedlyError: Socket closed unexpectedly or Error: connect ECONNREFUSED [IP]:[PORT]
reconnecting	The client is trying to reconnect to the server.	No argument

The client will not emit any other events beyond those listed above.

Supported Redis versions

Node Redis is supported with the following versions of Redis:

Version	Supported
7.0.z	:heavy_check_mark:
6.2.z	:heavy_check_mark:
6.0.z	:heavy_check_mark:
5.0.z	:heavy_check_mark:
< 5.0	:x:

Node Redis should work with older versions of Redis, but it is not fully tested and we cannot offer support.

Contributing

If you'd like to contribute, check out the contributing guide.

Thank you to all the people who already contributed to Node Redis!

License

This repository is licensed under the "MIT" license. See LICENSE.