amqp-node/examples/tutorials/rpc_client.js

An AMQP 0-9-1 (e.g., RabbitMQ) library and client.

#!/usr/bin/env node

var amqp = require('amqplib');
var basename = require('path').basename;
var when = require('when');
var defer = when.defer;
var uuid = require('node-uuid');

// I've departed from the form of the original RPC tutorial, which
// needlessly introduces a class definition, and doesn't even
// parameterise the request.

var n;
try {
  if (process.argv.length < 3) throw Error('Too few args');
  n = parseInt(process.argv[2]);
}
catch (e) {
  console.error(e);
  console.warn('Usage: %s number', basename(process.argv[1]));
  process.exit(1);
}

amqp.connect('amqp://localhost').then(function(conn) {
  return when(conn.createChannel().then(function(ch) {
    var answer = defer();
    var corrId = uuid();
    function maybeAnswer(msg) {
      if (msg.properties.correlationId === corrId) {
        answer.resolve(msg.content.toString());
      }
    }

    var ok = ch.assertQueue('', {exclusive: true})
      .then(function(qok) { return qok.queue; });

    ok = ok.then(function(queue) {
      return ch.consume(queue, maybeAnswer, {noAck: true})
        .then(function() { return queue; });
    });
    
    ok = ok.then(function(queue) {
      console.log(' [x] Requesting fib(%d)', n);
      ch.sendToQueue('rpc_queue', new Buffer(n.toString()), {
        correlationId: corrId, replyTo: queue
      });
      return answer.promise;
    });

    return ok.then(function(fibN) {
      console.log(' [.] Got %d', fibN);
    });
  })).ensure(function() { conn.close(); });
}).then(null, console.warn);