amqplib-rpc

Thin Amplib utils for RabbitMQ RPC in Node.js. Uses replyTo and correlationId message properties as the RabbitMQ rpc tutorial suggests.

Installation

npm i --save amqplib-rpc

Usage

request

Make an rpc request, publish a message to an rpc queue.

• Creates a channel, queue, correlationId, and sets up properties.replyTo and properties.correlationId on request message.

/**
  * @param  {AmqplibConnection}   connection     rabbitmq connection
  * @param  {String}   queue     name of rpc-queue to send the message to
  * @param  {Buffer}   content   message content
  * @param  {Object}   [opts]  sendToQueue options
  * @param  {Object}   [opts.timeout]  timeout in ms, will reject w/ TimeoutError, default: undefined (no timeout)
  * @param  {Object}   [opts.sendOpts]  sendToQueue options
  * @param  {Object}   [opts.queueOpts] assertQueue options for replyTo queue, queueOpts.exclusive defaults to true
  * @param  {Object}   [opts.consumeOpts] consume options for replyTo queue, consumeOpts defaults to ''
  * @param  {Object}   [opts.exchangeName] exchange name for request, exchangeName defaults to default exchange ('')
  * @param  {Function} [cb] optional callback, if using callback api
  * @return {Promise}  returns a promise, if using promise api
  */

request examples, rpc client

// Promise api example
var amqplib = require('amqplib')
var request = require('amqplib-rpc').request

amqplib.connect().then(function (connection) {
  return request(connection, 'multiply-queue', { a: 10, b: 20 }).then(function (replyMessage) {
    console.log(replyMessage.content.toString()) // 200
  })
})
.catch(...)

// Callback api example
var amqplib = require('amqplib/callback_api')
var request = require('amqplib-rpc').request

amqplib.connect(function (err, connection) {
  if (err) throw err
  var content = { a: 10, b: 20 } // gets converted to buffer automatically
  // RPC request
  request(connection, 'multiply-queue', content, function (err, replyMessage) {
    if (err) throw err
    console.log(replyMessage.content.toString()) // 200
  })
})

// Timeout Error example
// triggered by timeout option
var amqplib = require('amqplib')
var request = require('amqplib-rpc').request
var TimeoutError = require('amqplib-rpc').TimeoutError

amqplib.connect(function (err, connection) {
  if (err) throw err
  var content = { a: 10, b: 20 } // gets converted to buffer automatically
  var opts = { timeout: 100 }
  // RPC request
  request(connection, 'multiply-queue', content, opts, function (err, replyMessage) {
    console.log(err) // [TimeoutError: 'rpc timed out']
    console.log(err instanceof TimeoutError) // true
    console.log(err.data)
    /*
    {
      timeout: 100
      queue: 'multiplyQueue',
      content: { a: 10, b: 20 },
      opts: { // shows default opts in since only timeout was passed
        timeout: 100
        sendOpts: {},
        queueOpts: {
          exclusive: true
        },
        consumeOpts: {
          noAck: true
        }
      }
    }
    */
  })
})

// Channel Close Error example
// occurs if channel is closed before the response is received from rpc
var amqplib = require('amqplib')
var request = require('amqplib-rpc').request
var ChannelCloseError = require('amqplib-rpc').ChannelCloseError

amqplib.connect(function (err, connection) {
  if (err) throw err
  var content = { a: 10, b: 20 } // gets converted to buffer automatically
  var opts = { timeout: 100 }
  // RPC request
  request(connection, 'multiply-queue', content, opts, function (err, replyMessage) {
    console.log(err) // [ChannelCloseError: 'rpc channel closed before receiving the response message']
    console.log(err instanceof ChannelCloseError) // true
    console.log(err.data) // same as Timeout Error example above
  })
})

reply

Reply to an rpc request, publish a message to replyTo queue.

• Replies to a message using properties.replyTo and properties.correlationId.

• Reply will NOT error if the "replyTo" queue does not exist, if you need it to use checkReplyTo (example below).

• Reply will NOT ack the message. Ack/Nack must be done manually.

/**
 * @param  {AmqplibChannel} channel on which the message was recieved
 * @param  {Object} message incoming message on channel
 * @param  {Buffer|Object|Array|String} content message content
 * @param  {Object} opts publish options
 * @return {Boolean} replyWriteSuccess - amqplib docs do not mention this ever failing..
 */

reply example, rpc server

var amqplib = require('amqplib/callback_api')
var reply = require('amqplib-rpc').reply

amqplib.connect(function (err, connection) {
  if (err) throw err
  connection.createChannel(function (err, consumerChannel) {
    if (err) throw err
    connection.createChannel(function (err, publisherChannel) {
      if (err) throw err
      consumerChannel.consume('multiply-queue', messageHandler, function (err) {
        if (err) throw err
      })
      function messageHandler (message) {
        var json = JSON.parse(message.content.toString())
        var content = json.a * json.b // gets converted to buffer automatically
        var opts = {} // optional
        // RPC reply
        reply(publisherChannel, message, content, opts)
        // "ack" message
        consumerChannel.ack(message)
      }
    })
  })
})

checkReplyQueue

Create a channel, check if replyTo queue exists, and close the channel. checkReplyQueue creates it's own channel, bc checking for a non-existant queue errors and closes the channel.

/**
 * @param  {AmqpblibConnection}   connection amqplib rabbitmq connection
 * @param  {Object}   message    request queue message
 * @param  {Function} [cb]       not required if using promises
 * @return {Promise}  if using promises
 */

checkReplyQueue before reply example, rpc server

var amqplib = require('amqplib/callback_api')
var reply = require('amqplib-rpc').reply
var checkReplyQueue = require('amqplib-rpc').checkReplyQueue
var QueueNotFound = require('amqplib-rpc').QueueNotFound

amqplib.connect(function (err, connection) {
  if (err) throw err
  connection.createChannel(function (err, consumerChannel) {
    if (err) throw err
    connection.createChannel(function (err, publisherChannel) {
      if (err) throw err
      consumerChannel.consume('multiply-queue', messageHandler, function (err) {
        if (err) throw err
      })
      function messageHandler (message) {
        var json = JSON.parse(message.content.toString())
        var content = json.a * json.b // gets converted to buffer automatically
        var opts = {} // optional
        // Check replyTo queue exists, note: also support promise api
        checkReplyQueue(connection, message, function (err, exists) {
          if (err) throw err
          if (!exists) {
            // "replyTo" queue no longer exists
            // ack, nack, or etc.
            return
          }
          // RPC reply
          reply(publisherChannel, message, content, opts)
          // "ack" message
          consumerChannel.ack(message)
        })
      }
    })
  })
})

checkQueue

Create a channel, check if the queue exists, and close the channel. This is not rpc related but was implemented for checkReplyQueue, so I've exported it. In some cases, it may be useful to check if a queue exists before publishing to it.

/*
 * @param  {AmqpblibConnection}   connection amqplib rabbitmq connection
 * @param  {String}   queue    queue name
 * @param  {Function} [cb]     callback, not required if using promises
 * @return {Promise}  if using promises
 */

checkReplyQueue before reply example, rpc server

var amqplib = require('amqplib/callback_api')
var reply = require('amqplib-rpc').reply
var checkQueue = require('amqplib-rpc').checkQueue
var QueueNotFound = require('amqplib-rpc').QueueNotFound

amqplib.connect(function (err, connection) {
  if (err) throw err
  connection.createChannel(function (err, channel) {
    if (err) throw err
    var queue = 'some-queue'
    // Check replyTo queue exists, note: also support promise api
    checkQueue(connection, queue, function (err, exists) {
      if (err) throw err
      if (!exists) {
        // queue does not exist, do something special
        return
      }
      // publish message to queue
      channel.sendToQueue(queue, content)
    })
  })
})

Follows RabbitMQ RPC tutorial

https://www.rabbitmq.com/tutorials/tutorial-six-javascript.html

Changelog

CHANGELOG.md

License

MIT