Problem Statement

• No notification mechanism to get the virtual or physical resource state changes.
• CloudStack generates a action event and persists in the DB. By polling through listEvents API one can get to know the events that occur but there is no mechanism to enable push notifications.
• usage server which generated usage events tight coupled into orchestration 

Proposal

• introduce a state machine for all the virtual and physical resources which CloudStack manages and generate an event on state transition
•  
• Introduce a light weight event bus
• wildcard subscription

Use cases

• Usage/billing engines
• AMQP
• CMDB
• pub/sub notification service

Discussion topics

Implementation