RabbitMQ Client

Node.js client library for RabbitMQ. Publish messages, declare rules for routing those messages into queues, consume messages from queues.

Why not amqplib?

• No dependencies
• Automatically re-connect, re-subscribe, or retry publishing
• Optional higher-level Consumer/Publisher API for even more robustness
• Written in typescript and published with heavily commented type definitions
• See here for full API documentation
• Intuitive API with named parameters instead of positional
• "x-arguments" like "x-message-ttl" don't have camelCase aliases

Performance

Performance is comparable to amqplib (see ./benchmark.ts).

Quick start

In addition to the lower-level RabbitMQ methods, this library exposes two main interfaces, a Consumer and a Publisher (which should cover 90% of uses cases), as well as a third RPCClient for request-response communication.

import {Connection} from 'rabbitmq-client'

// Initialize:
const rabbit = new Connection('amqp://guest:guest@localhost:5672')
rabbit.on('error', (err) => {
  console.log('RabbitMQ connection error', err)
})
rabbit.on('connection', () => {
  console.log('Connection successfully (re)established')
})

// Consume messages from a queue:
// See API docs for all options
const sub = rabbit.createConsumer({
  queue: 'user-events',
  queueOptions: {durable: true},
  // handle 2 messages at a time
  qos: {prefetchCount: 2},
  // Optionally ensure an exchange exists
  exchanges: [{exchange: 'my-events', type: 'topic'}],
  // With a "topic" exchange, messages matching this pattern are routed to the queue
  queueBindings: [{exchange: 'my-events', routingKey: 'users.*'}],
}, async (msg) => {
  console.log('received message (user-events)', msg)
  // The message is automatically acknowledged (BasicAck) when this function ends.
  // If this function throws an error, then msg is rejected (BasicNack) and
  // possibly requeued or sent to a dead-letter exchange. You can also return a
  // status code from this callback to control the ack/nack behavior
  // per-message.
})

sub.on('error', (err) => {
  // Maybe the consumer was cancelled, or the connection was reset before a
  // message could be acknowledged.
  console.log('consumer error (user-events)', err)
})

// Declare a publisher
// See API docs for all options
const pub = rabbit.createPublisher({
  // Enable publish confirmations, similar to consumer acknowledgements
  confirm: true,
  // Enable retries
  maxAttempts: 2,
  // Optionally ensure the existence of an exchange before we use it
  exchanges: [{exchange: 'my-events', type: 'topic'}]
})

// Publish a message to a custom exchange
await pub.send(
  {exchange: 'my-events', routingKey: 'users.visit'}, // metadata
  {id: 1, name: 'Alan Turing'}) // message content

// Or publish directly to a queue
await pub.send('user-events', {id: 1, name: 'Alan Turing'})

// Clean up when you receive a shutdown signal
async function onShutdown() {
  // Waits for pending confirmations and closes the underlying Channel
  await pub.close()
  // Stop consuming. Wait for any pending message handlers to settle.
  await sub.close()
  await rabbit.close()
}
process.on('SIGINT', onShutdown)
process.on('SIGTERM', onShutdown)

Connection.createConsumer() vs Channel.basicConsume()

The above Consumer & Publisher interfaces are recommended for most cases. These combine a few of the lower level RabbitMQ methods (exposed on the Channel interface) and and are much safer to use since they can recover after connection loss, or after a number of other edge-cases you may not have imagined. Consider the following list of scenarios (not exhaustive):

• Connection lost due to a server restart, missed heartbeats (timeout), forced by the management UI, etc.
• Channel closed as a result of publishing to an exchange which does not exist (or was deleted), or attempting to acknowledge an invalid deliveryTag
• Consumer closed from the management UI, or because the queue was deleted, or because basicCancel() was called

In all of these cases you would need to create a new channel and re-declare any queues/exchanges/bindings before you can start publishing/consuming messages again. And you're probably publishing many messages, concurrently, so you'd want to make sure this setup only runs once per connection. If a consumer is cancelled then you may be able to reuse the channel but you still need to check the queue and so on...

The Consumer & Publisher interfaces abstract all of that away by running the necessary setup as needed and handling all the edge-cases for you.

Managing queues & exchanges

A number of management methods are available on the Connection interface; you can create/delete queues, exchanges, or bindings between them. It's generally safer to do this declaratively with a Consumer or Publisher. But maybe you just want to do something once.

const rabbit = new Connection()

await rabbit.queueDeclare({queue: 'my-queue', exclusive: true})

await rabbit.exchangeDeclare({queue: 'my-queue', exchange: 'my-exchange', type: 'topic'})

await rabbit.queueBind({queue: 'my-queue', exchange: 'my-exchange'})

const {messageCount} = await rabbit.queueDeclare({queue: 'my-queue', passive: true})

And if you really want to, you can acquire a raw AMQP Channel but this should be a last resort.

// Will wait for the connection to establish and then create a Channel
const ch = await rabbit.acquire()

// Channels can emit some events too (see documentation)
ch.on('close', () => {
  console.log('channel was closed')
})

const msg = ch.basicGet('my-queue')
console.log(msg)

// It's your responsibility to close any acquired channels
await ch.close()

RPCClient: request-response communication between services

This will create a single "client" Channel on which you may publish messages and listen for direct responses. This can allow, for example, two micro-services to communicate with each other using RabbitMQ as the middleman instead of directly via HTTP.

// rpc-server.js
const rabbit = new Connection()

const rpcServer = rabbit.createConsumer({
  queue: 'my-rpc-queue'
}, async (req, reply) => {
  console.log('request:', req.body)
  await reply('pong')
})

process.on('SIGINT', async () => {
  await rpcServer.close()
  await rabbit.close()
})

// rpc-client.js
const rabbit = new Connection()

const rpcClient = rabbit.createRPCClient({confirm: true})

const res = await rpcClient.send('my-rpc-queue', 'ping')
console.log('response:', res.body) // pong

await rpcClient.close()
await rabbit.close()