[rabbitmq-discuss] data being fetched from other queues too(that are not named in basicConsume)

[Kamal Nandan]

Dear Mostafa,

Thanks a lot for your help...

I followed your recommendation and its working well for me...

Thanks again.. :)

Thanks & Regards,
Kamal

From: Amr Mostafa [mailto:amr.mostafa at gmail.com]
Sent: Tuesday, April 12, 2011 8:54 PM
To: Kamal Nandan
Cc: Kamal; rabbitmq-discuss at lists.rabbitmq.com
Subject: Re: [rabbitmq-discuss] data being fetched from other queues too(that are not named in basicConsume)

Hi Kamal,

First off, if you want to use the asynchronous model then you don't need to use basicConsume with each message fetch. This is something that you do at the initialization of application/class, then you just use nextDelivery for fetching messages.

It appears to me that you should also use 3 consumers, one for each queue. Assuming they are called "highConsumer", "mediumConsumer" and "lowConsumer". Then to fetch the next available message from the "high" queue you should call: this.highConsumer.nextDelivery(), and so on.

I hope that gives you a better idea of what's wrong in your code.

Finally, there may be a way for you to

Regards,
On Tue, Apr 12, 2011 at 8:48 AM, Kamal Nandan <kamal.nandan at impetus.co.in<mailto:kamal.nandan at impetus.co.in>> wrote:
Hi Mustafa,

Thanks for your help...

Infact, I need an asynchronous version only so that my code doesn't keep on polling the server for new messages..

My query is, if we have done something like this:

boolean autoAck = false;

            System.out.println("fetching message from the Q: " + queueName + "\n");
            this.channel.basicConsume(queueName, autoAck, this.queueingConsumer);   // We are trying to fetch the data from the specified queue name only

            QueueingConsumer.Delivery delivery;

            try {
                  delivery = this.queueingConsumer.nextDelivery(timeout);     //Shouldn't this fetch the data from the specified queue only and not some other queue(s); FYI, the same channel has been bound to a no. of queues; I hope this is not the culprit???

            } catch (InterruptedException ie) {
                  return null;
            }
            if(delivery != null)
            {
                  channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
                  byte[] body = delivery.getBody();
                  return body;
            }
            else
            {
                  return null;
            }

Since, in "channel.basicConsume", I have passed the name of the queue from which data has to be fetched (and not other queues too to which the channel is bound to), the why do we get data from other queues too when we do "this.queueingConsumer.nextDelivery(timeout);".

Initially, I had used "basicGet", but that will be synchronous and that's the reason why I decided to use "basicConsume".

Please also see my comments in "RED".

Also, you can see a trimmed down version of my code here:
http://pastebin.com/zLJpUFHA


Thanks & Regards,
Kamal

From: rabbitmq-discuss-bounces at lists.rabbitmq.com<mailto:rabbitmq-discuss-bounces at lists.rabbitmq.com> [mailto:rabbitmq-discuss-bounces at lists.rabbitmq.com<mailto:rabbitmq-discuss-bounces at lists.rabbitmq.com>] On Behalf Of Amr Mostafa
Sent: Monday, April 11, 2011 7:32 PM
To: Kamal
Cc: rabbitmq-discuss at lists.rabbitmq.com<mailto:rabbitmq-discuss at lists.rabbitmq.com>
Subject: Re: [rabbitmq-discuss] data being fetched from other queues too(that are not named in basicConsume)

Hi Kamal,

It looks like you are mistaking Channel.basicConsume for Channel.basicGet. The first (which you are using) is asynchronous and what it does is subscribe a consumer with the messaging server on a given queue. All incoming messages to do that queue will be directly sent by the messaging server to that subscribed consumer. In the QueuingConsumer implementation, those received messages are held in an internal queue and you fetch them using nextDelivery.

This model is called subscription-based, another simpler approach is using Channel.basicGet. I advise you to check this for details:

http://www.rabbitmq.com/api-guide.html
On Mon, Apr 11, 2011 at 3:19 PM, Kamal <kamal.nandan at gmail.com<mailto:kamal.nandan at gmail.com>> wrote:
Hi,

I am facing a strange problem while using RabbitMq.

I have a consumer that creates 3 queues(just for name sake HIGH/MEDIUM/
LOW priority queues) on the RabbitMQ server and consumes data from the
3 queues in this order:
5 messages from HIGH
3 messages from MEDIUM
2 messages from LOW.

This keeps on happening in round-robin fashion.
If there is no data available on the respective queue, the data from
the next queue is fetched.

I am using "Channel.basicConsume(queueName, ACK, QueueingConsumer)"
and "QueueingConsumer.nextDelivery(timeout)" to fetch the data.

What I see here is: I see that the data is fetched from the other
queues too. i.e. Even though I have passed the queuename as "HIGH",
then too i see that the data is being fetched from the queue "LOW" or
"MEDIUM" and vice versa. I am finding this behaviour quite strange.
Can someone plz help me out with this.

Following is a snippet of my code.:
http://pastebin.com/s03dP91z

Thanks in advance..

Regards,
Kamal
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--
Amr Mostafa
Egypt Development Center
Member of NTG
Mobile: +(2012)1700502
Office: +(202)24052355/6 - Ext.: 2005

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--
Amr Mostafa
Egypt Development Center
Member of NTG
Mobile: +(2012)1700502
Office: +(202)24052355/6 - Ext.: 2005

________________________________

Are you exploring a Big Data Strategy ? Listen to this recorded webinar on Planning your Hadoop/ NoSQL projects for 2011 at www.impetus.com/featured_webinar?eventid=37

Follow us on www.twitter.com/impetuscalling or visit www.impetus.com to know more.


NOTE: This message may contain information that is confidential, proprietary, privileged or otherwise protected by law. The message is intended solely for the named addressee. If received in error, please destroy and notify the sender. Any use of this email is prohibited when received in error. Impetus does not represent, warrant and/or guarantee, that the integrity of this communication has been maintained nor that the communication is free of errors, virus, interception or interference.
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