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

Usage

Basic Example

import { createClient } from 'redis';

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

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

:warning: You MUST listen to error events. If a client doesn't have at least one error listener registered and an error occurs, that error will be thrown and the Node.js process will exit. See the EventEmitter docs for more details.

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', {
  expiration: {
    type: 'EX',
    value: 10
  },
  condition: 'NX'
});

NOTE: command modifiers that change the reply type (e.g. WITHSCORES for ZDIFF) are exposed as separate commands (e.g. ZDIFF_WITHSCORES/zDiffWithScores).

Replies will be mapped to useful data structures:

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

NOTE: you can change the default type mapping. See the Type Mapping documentation for more information.

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', 'EX', '10', 'NX']); // 'OK'
await client.sendCommand(['HGETALL', 'key']); // ['key1', 'field1', 'key2', 'field2']

Disconnecting

.close()

Gracefully close a client's connection to Redis. Wait for commands in process, but reject any new commands.

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

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

.close() is just like .quit() which was depreacted v5. See the relevant section in the migration guide for more information.

.destroy()

Forcibly close a client's connection to Redis.

try {
  const promise = Promise.all([
    client.ping(),
    client.get('key')
  ]);

  client.destroy();

  await promise;
} catch (err) {
  // DisconnectsClientError
}

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

.destroy() is just like .disconnect() which was depreated in v5. See the relevant section in the migration guide for more information.

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==')
]);

Connection State

To client exposes 2 booleans that track the client state:

1. isOpen - the client is either connecting or connected.
2. isReady - the client is connected and ready to send

Events

The client extends EventEmitter and emits the following events:

Name	When	Listener arguments
connect	Initiating a connection to the server	No arguments
ready	Client is ready to use	No arguments
end	Connection has been closed (via .quit() or .disconnect())	No arguments
error	An error has occurred—usually a network issue such as "Socket closed unexpectedly"	(error: Error)
reconnecting	Client is trying to reconnect to the server	No arguments
sharded-channel-moved	See here	See here

:warning: You MUST listen to error events. If a client doesn't have at least one error listener registered and an error occurs, that error will be thrown and the Node.js process will exit. See the EventEmitter docs for more details.

Read more

• Transactions (MULTI/EXEC).
• Pub/Sub.
• Scan Iterators.
• Programmability.
• Command Options.
• Pool.
• Clustering.
• Sentinel.
• FAQ.

Supported Redis versions

Node Redis is supported with the following versions of Redis:

Version	Supported
7.2.z	:heavy_check_mark:
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.