[Pulp-list] Messaging Questions

[Jason Dobies]

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For the mailing list purposes, we talked about some of this offline but
I'll comment in here too.

>> We will be using (I think) qpid for more then request/response.  I
>> expect we'll want the agent to broadcast (pub/sub) heartbeat messages. 
>> Also, on the server-side, we expect to broadcast (pub/sub) events
>> intended for system integration.  For example, integration between pulp
>> and candlepin.
> 
>> Also, message brokers provide queueing, reliable delivery and content
>> based messaging routing (just to name a few).

I wasn't specific enough in my question. I more meant why are we using
it for server RMI to the agent. All the things you bring up here sound
like great reasons for qpid.

>> Maybe asking some other questions will shed some light on whether we
>> need asynchronous request/response (callback) for agent operations.
> 
>> When asking a large collection of agents to perform an operation:
> 
>> Is this one async task or a task per consumer (agent)?

Ideally, I view group operations as simply calling the same operation on
each member of the group. I say "ideally" since that sort of approach is
often pretty crappy when it comes to performance.

Still, in this case I think it's one task per consumer/agent. That way
we know that "Package install failed on X and succeeded on Y and Z"
instead of just "Something went wrong. Somewhere."

>> Do we need to provide status of this operation for each agent?

I think so. I can picture a UI that shows in progress tasks across the
board, so we can eyeball how much more we have left to do. We may not
necessarily show "Installing package 54 of 182 on consumer X", but we
can at least see "consumer Y and Z are done, consumer X is working and
consumer W hasn't started yet".

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