[Pulp-list] Messaging Questions

Jeff Ortel jortel at redhat.com
Thu Jul 8 17:58:26 UTC 2010



On 07/08/2010 09:51 AM, Jason Dobies wrote:
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>> Yes it does.  If we stick with only synchronous requests to that agent
>> and leave asynchronous stuff to the pulp Task engine, temporary
>> (non-durable) queues will be a good approach to pruning dead queues.
>
> One more question on this and I'll shut up until the voice call. If all
> requests are synchronous, is this gonna scale? What happens when we fire
> off messages to 10K agents and/or if those requests take minutes (if not
> more) to execute? Even if it's executing in the async task queue, won't
> this be a fierce burden on the server (it may not be, I'm kinda thinking
> out loud here).

If the thinking is that:

asynchronous = pub/sub = efficiency

Then, an important consideration is: How does qpid implements *durable* subscription to 
topics (pub/sub)?  The durable nature of the subscription usually requires that brokers 
implement using queues where messages are routed to subscriber queues based on 
topic/subject and selectors.  Asynchronous request/response assumes guaranteed delivery. 
This means that the message must be queued so it can be delivered to consumers that are 
not connected when the message is published.  This is the definition of durable 
subscription.  So, publishing a message to 10k agents probably still requires 10k queues.

But, if we anticipate this kind of mass operation, then asynchronous will be much more 
efficient and worth the extra complexity because we can have all the agents performing the 
operation in parallel.  If we did this synchronously, we'd be limited to the Task thread 
limit.

>
>
> - --
> Jason Dobies
> RHCE# 805008743336126
> Freenode: jdob
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