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.
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
});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 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 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.
This is a complete Redis client for node.js. It supports all Redis commands, including MULTI, WATCH, and PUBLISH/SUBSCRIBE.
Install with:
npm install redis
For portability, a pure JavaScript reply parser is used by default. Pieter Noordhuis has provided a binding to the
official hiredis C library, which is non-blocking and fast. To use hiredis, do:
npm install hiredis redis
If hiredis is installed, node_redis will use it by default.
node_redis works in the latest versions of node, is published in npm, is used by many people, and is in production on a
number of sites.
node_redis was originally written to replace node-redis-client which hasn't been updated in a while, and no longer works
with recent versions of node.
Here are typical results of multi_bench.js which is similar to redis-benchmark from the Redis distribution.
It uses 50 concurrent connections with no pipelining.
JavaScript parser:
PING: 20000 ops 42283.30 ops/sec 0/5/1.182
SET: 20000 ops 32948.93 ops/sec 1/7/1.515
GET: 20000 ops 28694.40 ops/sec 0/9/1.740
INCR: 20000 ops 39370.08 ops/sec 0/8/1.269
LPUSH: 20000 ops 36429.87 ops/sec 0/8/1.370
LRANGE (10 elements): 20000 ops 9891.20 ops/sec 1/9/5.048
LRANGE (100 elements): 20000 ops 1384.56 ops/sec 10/91/36.072
hiredis parser:
PING: 20000 ops 46189.38 ops/sec 1/4/1.082
SET: 20000 ops 41237.11 ops/sec 0/6/1.210
GET: 20000 ops 39682.54 ops/sec 1/7/1.257
INCR: 20000 ops 40080.16 ops/sec 0/8/1.242
LPUSH: 20000 ops 41152.26 ops/sec 0/3/1.212
LRANGE (10 elements): 20000 ops 36563.07 ops/sec 1/8/1.363
LRANGE (100 elements): 20000 ops 21834.06 ops/sec 0/9/2.287
The performance of node_redis improves dramatically with pipelining.
Simple example, included as example.js:
var redis = require("redis"),
client = redis.createClient();
client.on("error", function (err) {
console.log("Error " + err);
});
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.quit();
});
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)$
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 client.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.
client will emit some events about the state of the connection to the Redis server.
client will emit connect when a connection is established to the Redis server.
Commands issued before the connect event are queued, then replayed when a connection is established.
client will emit error when encountering an error connecting to the Redis server.
Note that "error" is a special event type in node. If there are no listeners for an "error" event, node will exit. This is usually what you want, but it can lead to some cryptic error messages like this:
mjr:~/work/node_redis (master)$ node example.js
node.js:50
throw e;
^
Error: ECONNREFUSED, Connection refused
at IOWatcher.callback (net:870:22)
at node.js:607:9
Not very useful in diagnosing the problem, but if your program isn't ready to handle this, it is probably the right thing to just exit.
client will also emit error if an exception is thrown inside of node_redis for whatever reason.
It would be nice to distinguish these two cases.
client will emit end when an established Redis server connection has closed.
client will emit drain when the TCP connection to the Redis server has been buffering, but is now
writable. This event can be used to stream commands in to Redis and adapt to backpressure. Right now,
you need to check client.command_queue.length to decide when to reduce your send rate. Then you can
resume sending when you get drain.
client will emit idle when there are no outstanding commands that are awaiting a response.
Create a new client connection. port defaults to 6379 and host defaults
to 127.0.0.1. If you have redis-server running on the same computer as node, then the defaults for
port and host are probably fine. options in an object with the following possible properties:
parser: which Redis protocol reply parser to use. Defaults to hiredis if that module is installed.
This may also be set to javascript.return_buffers: defaults to false. If set to true, then bulk data replies will be returned as node Buffer
objects instead of JavaScript Strings.createClient() returns a RedisClient object that is named client in all of the examples here.
Forcibly 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.quit() to send the QUIT command after you have handled all replies.
This example closes the connection to the Redis server before the replies have been read. You probably don't want to do this:
var redis = require("redis"),
client = redis.createClient();
client.set("foo_rand000000000000", "some fantastic value");
client.get("foo_rand000000000000", function (err, reply) {
console.log(reply.toString());
});
client.end();
client.end() is useful for timeout cases where something is stuck or taking too long and you want
to start over.
Here is a simple example of the API for publish / subscribe. This program opens two client connections, subscribes to a channel on one of them, and publishes to that channel on the other:
var redis = require("redis"),
client1 = redis.createClient(), client2 = redis.createClient(),
msg_count = 0;
client1.on("subscribe", function (channel, count) {
client2.publish("a nice channel", "I am sending a message.");
client2.publish("a nice channel", "I am sending a second message.");
client2.publish("a nice channel", "I am sending my last message.");
});
client1.on("message", function (channel, message) {
console.log("client1 channel " + channel + ": " + message);
msg_count += 1;
if (msg_count === 3) {
client1.unsubscribe();
client1.end();
client2.end();
}
});
client1.incr("did a thing");
client1.subscribe("a nice channel");
When a client issues a SUBSCRIBE or PSUBSCRIBE, that connection is put into "pub/sub" 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 pub/sub mode, just open another connection.
If a client has subscriptions active, it may emit these events:
Client will emit message for every message received that matches an active subscription.
Listeners are passed the channel name as channel and the message Buffer as message.
Client will emit pmessage for every message received that matches an active subscription pattern.
Listeners are passed the original pattern used with PSUBSCRIBE as pattern, the sending channel
name as channel, and the message Buffer as message.
Client will emit subscribe in response to a SUBSCRIBE command. Listeners are passed the
channel name as channel and the new count of subscriptions for this client as count.
Client will emit psubscribe in response to a PSUBSCRIBE command. Listeners are passed the
original pattern as pattern, and the new count of subscriptions for this client as count.
Client will emit unsubscribe in response to a UNSUBSCRIBE command. Listeners are passed the
channel name as channel and the new count of subscriptions for this client as count. When
count is 0, this client has left pub/sub mode and no more pub/sub events will be emitted.
Client will emit punsubscribe in response to a PUNSUBSCRIBE command. Listeners are passed the
channel name as channel and the new count of subscriptions for this client as count. When
count is 0, this client has left pub/sub mode and no more pub/sub events will be emitted.
MULTI commands are queued up until an EXEC is issued, and then all commands are run atomically by
Redis. The interface in node_redis is to return an individual Multi object by calling client.multi().
var redis = require("./index"),
client = redis.createClient(), set_size = 20;
client.sadd("bigset", "a member");
client.sadd("bigset", "another member");
while (set_size > 0) {
client.sadd("bigset", "member " + set_size);
set_size -= 1;
}
// multi chain with an individual callback
client.multi()
.scard("bigset")
.smembers("bigset")
.keys("*", function (err, replies) {
client.mget(replies, redis.print);
})
.dbsize()
.exec(function (err, replies) {
console.log("MULTI got " + replies.length + " replies");
replies.forEach(function (reply, index) {
console.log("Reply " + index + ": " + reply.toString());
});
});
client.multi() is a constructor that returns a Multi object. Multi objects share all of the
same command methods as client objects do. Commands are queued up inside the Multi object
until Multi.exec() is invoked.
You can either chain together MULTI commands as in the above example, or you can queue individual
commands while still sending regular client command as in this example:
var redis = require("redis"),
client = redis.createClient(), multi;
// start a separate multi command queue
multi = client.multi();
multi.incr("incr thing", redis.print);
multi.incr("incr other thing", redis.print);
// runs immediately
client.mset("incr thing", 100, "incr other thing", 1, redis.print);
// drains multi queue and runs atomically
multi.exec(function (err, replies) {
console.log(replies); // 101, 2
});
// you can re-run the same transaction if you like
multi.exec(function (err, replies) {
console.log(replies); // 102, 3
client.quit();
});
In addition to adding commands to the MULTI queue individually, you can also pass an array
of commands and arguments to the constructor:
var redis = require("redis"),
client = redis.createClient(), multi;
client.multi([
["mget", "multifoo", "multibar", redis.print],
["incr", "multifoo"],
["incr", "multibar"]
]).exec(function (err, replies) {
console.log(replies);
});
Some other things you might like to know about.
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.
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.
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.
Boolean tracking the state of the connection to the Redis server.
The number of commands that have been sent to the Redis server but not yet replied to. You can use this to enforce some kind of maximum queue depth for commands while connected.
Don't mess with client.command_queue though unless you really know what you are doing.
The number of commands that have been queued up for a future connection. You can use this to enforce some kind of maximum queue depth for pre-connection commands.
Current delay in milliseconds before a connection retry will be attempted. This starts at 250.
Multiplier for future retry timeouts. This should be larger than 1 to add more time between retries. Defaults to 1.7. The default initial connection retry is 250, so the second retry will be 425, followed by 723.5, etc.
Stream large set/get values into and out of Redis. Otherwise the entire value must be in node's memory.
Performance can be better for very large values.
I think there are more performance improvements left in there for smaller values, especially for large lists of small values.
Some people have have added features and fixed bugs in node_redis other than me.
In order of first contribution, they are:
Thanks.
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.
FAQs
A modern, high performance Redis client
The npm package redis receives a total of 3,171,167 weekly downloads. As such, redis popularity was classified as popular.
We found that redis demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 4 open source maintainers collaborating on the project.
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