RabbitMQ - Non Blocking Consumer with Manual Acknowledgement

Question

I'm just starting to learn RabbitMQ so forgive me if my question is very basic.

My problem is actually the same with the one posted here: RabbitMQ - Does one consumer block the other consumers of the same queue?

However, upon investigation, i found out that manual acknowledgement prevents other consumers from getting a message from the queue - blocking state. I would like to know how can I prevent it. Below is my code snippet.

...

var message = receiver.ReadMessage();
Console.WriteLine("Received: {0}", message);

// simulate processing
System.Threading.Thread.Sleep(8000);

receiver.Acknowledge();

public string ReadMessage()
{

   bool autoAck = false;
   Consumer = new QueueingBasicConsumer(Model);
   Model.BasicConsume(QueueName, autoAck, Consumer);
   _ea = (BasicDeliverEventArgs)Consumer.Queue.Dequeue();
   return Encoding.ASCII.GetString(_ea.Body);
}

public void Acknowledge()
{

   Model.BasicAck(_ea.DeliveryTag, false);
}

Answer 1

I modify how I get messages from the queue and it seems blocking issue was fixed. Below is my code.

    public string ReadOneAtTime()
    {
        Consumer = new QueueingBasicConsumer(Model);
        var result = Model.BasicGet(QueueName, false);
        if (result == null) return null;
        DeliveryTag = result.DeliveryTag;
        return Encoding.ASCII.GetString(result.Body);
    }

    public void Reject()
    {
        Model.BasicReject(DeliveryTag, true);
    }

    public void Acknowledge()
    {
        Model.BasicAck(DeliveryTag, false);
    }

Going back to my original question, I added the QOS and noticed that other consumers can now get messages. However some are left unacknowledged and my program seems to hangup. Code changes are below:

    public string ReadMessage()
    {
        Model.BasicQos(0, 1, false); // control prefetch
        bool autoAck = false;
        Consumer = new QueueingBasicConsumer(Model);
        Model.BasicConsume(QueueName, autoAck, Consumer);

        _ea = Consumer.Queue.Dequeue();
        return Encoding.ASCII.GetString(_ea.Body);
    }

    public void AckConsume()
    {
        Model.BasicAck(_ea.DeliveryTag, false);
    }

    In Program.cs
    private static void Consume(Receiver receiver)
    {
        int counter = 0;
        while (true)
        {
            var message = receiver.ReadMessage();
            if (message == null)
            {
                Console.WriteLine("NO message received.");
                break;
            }
            else
            {
                counter++;
                Console.WriteLine("Received: {0}", message);
                receiver.AckConsume();
            }
        }

        Console.WriteLine("Total message received {0}", counter);
    }

I appreciate any comments and suggestions. Thanks!