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From Kelven Yang <>
Subject Re: [Discuss] CloudStack architecture to a loosely-coupled component oriented distributed architecture
Date Tue, 21 Aug 2012 04:49:40 GMT

On 8/20/12 9:33 PM, "Murali Reddy" <> wrote:

>On 20/08/12 11:23 PM, "Kelven Yang" <> wrote:
>>The key point is the shifting to event-driven programming model itself at
>>orchestration layer, the underlying facility is currently not at critical
>>path, we will need to do a messaging arbitration here so that we can
>>plugin a suitable MQ selection in a fairly easy step. One thing I'm sure
>>is that we won't use two separated MQ solutions in one system.
>Agree. Underlaying messaging infrastructure is not much of concern, but my
>point was we need to have message abstraction (be it for IPC, event
>notifications) requirements so that we know what to expect from middleware
>when we need to choose.
>>We also need to think twice of tight-coupled listener pattern across
>>components, if listeners from different components are implicitly
>>to participate application level transaction across components, it should
>>better be done through an orchestration process.

>IMO, I think we need to move away from listener-callback paradigm in
>distributed environment.

This is exactly what I meant.

>Good thing is its not used much and is not
>required for event notification framework as well. Its good if we have
>request-response messaging pattern. I am thinking aloud, in enterprise
>environments it can enable 3rd party components to integrate workflows in
>orchestrations in a loosely coupled manner. For e.g. On Vm starting event
>message, external workflow software can provision resources like IP, name,
>user creds etc provide a response which can be used to provision the Vm
>with provided details.



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