ACS is now comprised of a hierarchy of spring application contexts.
Each plugin can contribute configuration files to add to an existing
module or create it's own module.
Additionally, for the mgmt server, ACS custom AOP is no longer used
and instead we use Spring AOP to manage interceptors.
The managed context framework provides a simple way to add logic
to ACS at the various entry points of the system. As threads are
launched and ran listeners can be registered for onEntry or onLeave
of the managed context. This framework will be used specifically
to handle DB transaction checking and setting up the CallContext.
This framework is need to transition away from ACS custom AOP to
Spring AOP.
following changes
- introduced notion of event bus with publish, subscribe, unsubscribe
semantics
- a plug-in can implement the EventBus abstraction to provide event
bug to CloudStack
- A rabbitMQ based plug-in that can interact with AMQP servers to
provide message broker based event-bug
- stream lines, action events, usage events, alerts publishing in to
convineance classed which are also used to publish corresponding
event on to event bus
- introduced notion of state change event. On a state change, in the
state machine corrsponding to the resource, a state change event is
published on the event bug
- associated a state machined with Snapshot and Network objects
- Virtual Machine, Volume, Snaphost, Network object state changes wil
result in a state change event
