// index.js
var amqp = require('amqp');

var connection = null;

connection = amqp.createConnection({ host: 'foo.com' });

connection.on('ready', function () {
  connection.queue('loc', { durable: true, autoDelete: false}, function(q) {
    q.bind('main', 'loc');
    q.subscribe({ack:true, prefetchCount: 0}, function (message, headers, deliveryInfo) {
      console.log(message);
      setTimeout(function() { q.shift(); }, 100);
    });
  });
});

my worker crashes only I run it AFTER there are messages in the queue. if I run the worker BEFORE, everything is ok.

I use ab to add 2 messages to the queue:
ab -k -n 2 -c 1 -p post-data -T 'application/json' foo-api.com/publish

And now run my worker - node index.js
here is the outputs:

{ topic: 'loc',
  sourceCode: 'LOC',
  sourceRecordID: '690599224',
  sourceField: 'Phone',
  sourceFieldValue: '7572007395',
  actionCode: 'DISP',
  actionDescription: 'Disconnected Phone Number'
}
{ topic: 'loc',
  sourceCode: 'LOC',
  sourceRecordID: '690599224',
  sourceField: 'Phone',
  sourceFieldValue: '7572007395',
  actionCode: 'DISP',
  actionDescription: 'Disconnected Phone Number'
}

events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: PRECONDITION_FAILED - unknown delivery tag 2
    at Queue._onMethod (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:1979:15)
    at Queue.Channel._onChannelMethod (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:1557:14)
    at Connection._onMethod (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:1088:28)
    at AMQPParser.parser.onMethod (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:897:12)
    at AMQPParser._parseMethodFrame (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:451:10)
    at frameEnd (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:192:16)
    at frame (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:177:14)
    at AMQPParser.header [as parse] (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:163:14)
    at AMQPParser.execute (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:236:21)
    at Connection.<anonymous> (/Users/ogolan/projects/quai-loc/worker/node_modules/amqp/amqp.js:935:14)