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From Murali Reddy <>
Subject [PROPOSAL] Event notification framework
Date Thu, 09 Aug 2012 14:45:49 GMT

In continuation to the disucssion [1] to have publisher/subscriber event
notification mechanism in CloudStack I am proposing a framework for
delivering events to the in-process subscribers. This is slightly
in-contrast to the earlier discussion to have native rich notification
(callback, SMS, email) systems and use of AMQP message brokers etc. Goal
of this proposal is to have minimal event notification mechanism in the
CloudStack core using which more powerful and flexible notification
system, monitoring systems can be build on top of this mechanism.

I am proposing below changes. Please refer to [2] for detailed proposal.
Please comment on proposal if you see any flaws, or have better

  - for all the virtual and physical resource CloudStack manages,
associate a state machine and for every state change publish relevent event
  - introduce a light weight event bus, on which events are published by
publishers. Event bus will be responsible for event delivery to the

I am planning to work on introducing these changes post ASF 4.0 release.
As reference implementation I am planning to move the usage component code
that is spread across the CloudStack components in to a usage plug-in that
will be subscriber of the events through event bus. Once the framework is
in place if any one is interested in building AMQP plug-in I would like to
hear their thoughts.



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