[rabbitmq-discuss] Data is feteched from the queue in random order

[Kamal Nandan]

Hi,

I am trying to dequeue data from the RabbitMQ. Why is it so that the data is not dequeued in the same order in which it was enqueued into the queue?

I see that the data is dequeued in a random order. Is it an expected behavior?

Following is the block of code that I am using to dequeue:


      public int init(String hostName, int port, String userName, String password, String queueName) throws OceRecoverableException
      {
            if(true == LOG.isDebugEnabled()) {
                  LOG.debug("Executing RabbitMqConsumer::init");
            }

            try {
                  super.initialize(hostName, port, userName, password, queueName);
            } catch (IOException ioe) {
                  String message = "RabbitMQ consumer failed to create connection with the RabbitMQ server.";
                  LOG.error( message + " [ERROR: " + ioe.getMessage() + "]");
                  throw new OceRecoverableException(ioe);
            }

            this.queueingConsumer = new QueueingConsumer(this.channel); //channel is the member of parent class

            try {
                  this.channel.basicConsume(queueName, false, this.queueingConsumer);
            } catch(IOException ioe) {
                  String message = "RabbitMQ consumer failed to set the QueueingConsumer callback for consuming data.";
                  LOG.error( message + " [ERROR: " + ioe.getMessage() + "]");
                  throw new OceRecoverableException(ioe);
            }

            return 0;
      }


      public byte[] fetchMessage(int timeout) throws OceRecoverableException
      {
            LOG.debug("RabbitMqConsumer::fetchMessage");

            if(this.channel == null)
            {
                  throw new OceRecoverableException("The channel is not initialized; Initilize the channel by calling init method");
            }

            QueueingConsumer.Delivery delivery;

            try {
                  delivery = this.queueingConsumer.nextDelivery(timeout);
            } catch(Exception ex) {
                  String message = "Error occurred while fetching data from the RabbitMQ server.";
                  LOG.error( message + " [ERROR: " + ex.getMessage() + "]");
                  throw new OceRecoverableException(ex);
            }

            if(delivery != null)
            {
                  try {
                        this.channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
                  } catch (IOException ioe) {
                        String message = "Error occurred while sending acknowledgement to the RabbitMQ server for the fetched message.";
                        LOG.error( message + " [ERROR: " + ioe.getMessage() + "]");
                        throw new OceRecoverableException(ioe);
                  }

                  byte[] body = delivery.getBody();
                  return body;
            }
            else
            {
                  return null;
            }
      }

}


It would be great, if someone could guide me regarding this?  I want the data to be fetched in the order it was enqueued.

Thanks & Regards,
Kamal

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