node-amqp worker/producer which print their effectiveness

producer.js

var amqp = require('amqp'),
    util = require('util');

var con = amqp.createConnection();

con.on('ready', function () {
  con.exchange('new-users', {type: 'fanout', confirm: true}, function (ex) {
    ex.setMaxListeners(100);

    var counter = 0,
        lastSeenCounter = 0,
        failed = 0,
        unconfirmed = 0,
        msgs = 250;
    
    setInterval(function() {
      var since = counter - lastSeenCounter;
      console.log('Seq:', counter, 'Rate:', since, 'Unconfirmed:', unconfirmed, 'Failed:', failed, '(msgs:', msgs, ')');

      if (failed > 0) {
        msgs -= 30;
      }
      else if (unconfirmed < 15) 
      {
        msgs++;
      } else {
        msgs -= (unconfirmed > 30) ? 10 : 1;
      }
      msgs = Math.max(msgs, 1);

      failed = 0;
      lastSeenCounter = counter;
    }, 1000);

    function loop() {
      var msg = {
        counter: counter++
      };

      ex.publish('', msg, {}, function (err) {
        if (err) {failed++;}
        unconfirmed--;
      });
      unconfirmed++;
      
      setTimeout(loop, 1000 / msgs);
    }
    loop();
 });
});

worker.js

var amqp = require('amqp'),
    util = require('util');

var con = amqp.createConnection();

con.on('ready', function () {
  var queueOptions = {
    durable: true,
    exclusive: false
  };
  con.queue('shinid.worker.in', queueOptions, function (q) {
    q.bind('new-users', '');
    var messagesSeen = 0,
        lastPrintSeen = 0;
        lastCounter = 0,
        highestCounter = 0,
        unack = 0;
    
    setInterval(function() {
      messagesSince = (messagesSeen - lastPrintSeen) / 2; // NOTE: We print every two seconds ;)
      console.log('Seen:', messagesSeen, 'Last:', lastCounter, 'Highest:', highestCounter, 'unack:', unack, 'msgs/s:', messagesSince);

      lastPrintSeen = messagesSeen;
    }, 2 * 1000);

    q.subscribe({ack: true, prefetchCount: 20}, function (json, headers, delivery, rawMessage) {
      messagesSeen++;
      lastCounter = json.counter;

      if (json.counter > highestCounter) {
        if (json.counter > highestCounter + 10) {
          console.log('Jumped', (json.counter - highestCounter));
        }
        highestCounter = json.counter;
      }
      
      if (json.counter < lastCounter) {
        console.log('Out-of-Order', highestCounter, json.counter);
      }

      unack++;
      setTimeout(function () {
        unack--;
        rawMessage.acknowledge();
      }, 16 * Math.random());

    });
  });
});