Multiple messages are not received if ack mode is not set - node.js

Question

I am using amqp-connection-manager given here
My code for reciever.js is as shown below :
var QUEUE_NAME = 'test';
var amqp = require('amqp-connection-manager');
// Handle an incomming message.
var onMessage = function (data) {
var message = JSON.parse(data.content.toString());
console.log("receiver: got message", message);
//channelWrapper.ack(data);
}
// Create a connetion manager
var connection = amqp.connect([process.env.CLOUDAMQP_MQTT_URL], {reconnectTimeInSeconds: 2, json: true});
connection.on('connect', function () {
console.log('Connected!');
});
connection.on('disconnect', function (params) {
console.log('Disconnected.', params.err.stack);
});
// Set up a channel listening for messages in the queue.
var channelWrapper = connection.createChannel({
setup: function (channel) {
// `channel` here is a regular amqplib `ConfirmChannel`.
return Promise.all([
channel.assertQueue(QUEUE_NAME, {durable: true}),
channel.prefetch(1),
channel.consume(QUEUE_NAME, onMessage)
]);
}
});
channelWrapper.waitForConnect()
.then(function () {
console.log("Listening for messages");
});
Now here whats happens is if I don't write channelWrapper.ack(data) , it stops receiving messages. So how can I enable receiving messages without writing channelWrapper.ack(data) .

Answer 1

That is because you are setting the prefetch value to 1. Prefetch is the number of unacknowledged messages you can have on a channel or on a queue (depends on the configuration) before receiving any more message.
You can change the prefetch value by changing this line in your code:
channel.prefetch(1)
With your current setup, you have to ack the messages eventually to be able to get more messages. If you are doing some async work with this message and acknowledge it later when the async work is done but do not want to wait for it to get other messages, you can just set the prefetch count to a reasonable amount.
If you are really sure that you don't need to ack the messages you can tell the broker not to expect an acknowledgement by noAck: true, just change this line:
channel.assertQueue(QUEUE_NAME, {durable: true, noAck: true})