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

---

Installation

npm install redis@next

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

Usage

Basic Example

import { createClient } from 'redis';

(async () => {
    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]:

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

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

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']

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'
);

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');

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

Lua Scripts

Define new functions using Lua scripts which execute on the Redis server:

import { createClient, defineScript } from 'redis';

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

    await client.connect();

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

Cluster

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 non-clustered client:

import { createCluster } from 'redis';

(async () => {
    const cluster = createCluster({
        rootNodes: [{
            host: '10.0.0.1',
            port: 30001
        }, {
            host: '10.0.0.2',
            port: 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');
})();

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==')
]);

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.