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

redis - a node redis client

This is a Redis client for node. It is designed for node 0.2.1+ and redis 2.0.1+. It probably won't work on earlier versions of either.

Most Redis commands are implemented, including MULTI. The notable exceptions are PUBLISH/SUBSCRIBE, and WATCH/UNWATCH. These should be coming soon.

Why?

node_redis works in the latest versions of node, is published in npm, and is very fast.

The most popular Redis client, redis-node-client by fictorial, is very mature and well tested. If you are running an older version of node or value the maturity and stability of redis-node-client, I encourage you to use that one instead.

node_redis is designed with performance in mind. The included test.js runs similar tests to redis-benchmark, included with the Redis distribution, and test.js is faster than redis-benchmarks for some patterns and slower for others. node_redis is roughly 6X faster at these benchmarks than redis-node-client.

Usage

Simple example, included as example.js:

var redis = require("redis"),
    client = redis.createClient();

client.set("string key", "string val", redis.print);
client.hset("hash key", "hashtest 1", "some value", redis.print);
client.hset(["hash key", "hashtest 2", "some other value"], redis.print);
client.hkeys("hash key", function (err, replies) {
    console.log(replies.length + " replies:");
    replies.forEach(function (reply, i) {
        console.log("    " + i + ": " + reply);
    });
    client.end();
});

This will display:

mjr:~/work/node_redis (master)$ node example.js 
Reply: OK
Reply: 0
Reply: 0
2 replies:
    0: hashtest 1
    1: hashtest 2
mjr:~/work/node_redis (master)$ 

Sending Commands

Each Redis command is exposed as a function on the client object. All functions take either take either an args Array plus optional callback Function or a variable number of individual arguments followed by an optional callback. Here is an example of passing an array of arguments and a callback:

client.mset(["test keys 1", "test val 1", "test keys 2", "test val 2"], function (err, res) {});

Here is that same call in the second style:

client.mset("test keys 1", "test val 1", "test keys 2", "test val 2", function (err, res) {});

Note that in either form the callback is optional:

client.set("some key", "some val");
client.set(["some other key", "some val"]);

For a list of Redis commands, see Redis Command Reference

The commands can be specified in uppercase or lowercase for convenience. client.get() is the same as clieint.GET().

Minimal parsing is done on the replies. Commands that return a single line reply return JavaScript Strings, integer replies return JavaScript Numbers, "bulk" replies return node Buffers, and "multi bulk" replies return a JavaScript Array of node Buffers. HGETALL returns an Object with Buffers keyed by the hash keys.

MULTI is supported. The syntax is a little awkward:

client.multi([
    ["incr", ["multibar"], function (err, res) {
        console.log(err || res);
    }],
    ["incr", ["multifoo"], function (err, res) {
        console.log(err || res);
    }]
]);

MULTI takes an Array of 3-element Arrays. The elements are: command, args, callback. When the commands are all submitted, EXEC is called and the callbacks are invoked in order. If a command is submitted that doesn't pass the syntax check, it will be removed from the transaction.

I guess we also need a callback when MULTI finishes, in case the last command gets removed from an error.

API

Events

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

"connect"

client will emit connect when a connection is established to the Redis server.

"error"

client will emit error when encountering an error connecting to the Redis server.

"end"

client will emit end when an established Redis server connection has closed.

redis.createClient(port, host)

Create a new client connection. port defaults to 6379 and host defaults to 127.0.0.1. If you have Redis running on the same computer as node, then the defaults are probably fine.

createClient returns a RedisClient object that is named client in all of the examples here.

client.end()

Close the connection to the Redis server. Note that this does not wait until all replies have been parsed. If you want to exit cleanly, call client.end() in the reply callback of your last command:

var redis = require("redis"),
    client = redis.createClient();

client.on("connect", function () {
    client.set("foo_rand000000000000", "some fantastic value");
    client.get("foo_rand000000000000", function (err, reply) {
        console.log(reply.toString());
        client.end();
    });
});

redis.print()

A handy callback function for displaying return values when testing. Example:

var redis = require("redis"),
    client = redis.createClient();

client.on("connect", function () {
    client.set("foo_rand000000000000", "some fantastic value", redis.print);
    client.get("foo_rand000000000000", redis.print);
});

This will print:

Reply: OK
Reply: some fantastic value

Note that this program will not exit cleanly because the client is still connected.

redis.debug_mode

Boolean to enable debug mode and protocol tracing.

var redis = require("redis"),
    client = redis.createClient();

redis.debug_mode = true;

client.on("connect", function () {
    client.set("foo_rand000000000000", "some fantastic value");
});

This will display:

mjr:~/work/node_redis (master)$ node ~/example.js 
send command: *3
$3
SET
$20
foo_rand000000000000
$20
some fantastic value

on_data: +OK

send command is data sent into Redis and on_data is data received from Redis.

client.send_command(command_name, args, callback)

Used internally to send commands to Redis. For convenience, nearly all commands that are published on the Redis Wiki have been added to the client object. However, if I missed any, or if new commands are introduced before this library is updated, you can use send_command() to send arbitrary commands to Redis.

All commands are sent as multi-bulk commands. args can either be an Array of arguments, or individual arguments, or omitted completely.

TODO

Need to implement PUBLISH/SUBSCRIBE

Need to implement WATCH/UNWATCH

Add callback for MULTI completion.

Support variable argument style for MULTI commands.

Stream binary data into and out of Redis.

Also

This library still needs a lot of work, but it is useful for many things. There are other Redis libraries available for node, and they might work better for you.

Comments and patches welcome.

LICENSE - "MIT License"

Copyright (c) 2010 Matthew Ranney, http://ranney.com/

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.