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From "Das, Kapali Tejeswar" <tejeswar....@iona.com>
Subject RE: [java] Question on implementing queue browsing
Date Tue, 05 Dec 2006 21:44:54 GMT
Carl,

I didn't find queue browsing mentioned in the AMQP 0.8 spec. That
explains the fact that there is no implementation in Qpid to browse the
messages in the queue.

My work is essentially to implement the JMS QueueBrowser feature that
would return a java.util.Enumeration which the caller uses to browse the
messages. JMS doesn't provide any guideline as to how it should be
implemented. Ideally, we may want to take the snapshot of all the
messages in the queue and present to the user. That way it (browsing)
won't have any effect on any other threads that are actively
producing/consuming messages.

In order to build the snapshot of the messages, we need to be able to
read a message without removing it from the queue. SynchronousQueue
doesn't support this.

Any feedback is greatly appreciated.

Thanks and regards
Tej


-----Original Message-----
From: Carl Trieloff [mailto:cctrieloff@redhat.com] 
Sent: Tuesday, December 05, 2006 3:12 PM
To: qpid-dev@incubator.apache.org
Subject: Re: [java] Question on implementing queue browsing



Tim Fox wrote:
>
>
> Das, Kapali Tejeswar wrote:
>> I am currently working on implementing the JMS queue browsing
>> functionality. Qpid uses java.util.concurrent.SynchronousQueue for
its
>> internal queue for enqueing and dequeing messages. This class doesn't
>> allow to peek/browse messages in the queue. It only has methods to
put a
>> message or get a message (with a timeout).
>
> Right. Also, for JMS, you'll need to implement some kind of priority 
> queue, which SynchronousQueue won't handle.

Tej,

In most use cases queue browsing can be counter productive for clients 
that want throughput or guarantees so we should not penalize the 
non-browsing and priority use cases. I also think that we might need to 
add to specification to complete this as I don't think it can be done on

0-8 without being very hacky ...  Have you been able to map this through

the current specification or is the starting point to define a peek cmd 
needed in the spec that we can provide to the working group. The 
interaction pattern and semantics between peeking the queue and messages

being removed needs also be defined.


Carl.



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