Convergence Observer

As a step toward implementing the convergence specification, Heat will split operations which fall into the “observing reality” category into a separate “observer” process.

Problem description

External systems hosting the physical resources of a stack will change independent of operations in Heat. There is a need to have a way to record and respond to these changes.

Proposed change

  • Observer is responsible for managing the model of reality

    • polls nova/neutron/etc using resource check methods.

    • conceptually polls heat stack descriptions to update internal resources

  • Data model will need to store “observed state”

  • REST API will need to display “observed state”

Note that no change will be necessary to the resource plugin API. Also note that subscribing to notifications will be done in a separate blueprint named convergence-continuous-observer.




Work should be spread between all developers as much as possible to help spread awareness of how things work.


Target Milestone for completion:


Work Items

  • Modify data model to record resource state

  • Modify public API to display observed state

  • Create new observer RPC API calls

  • Create new observer entry point

  • Move “check_active” and “check” calls to use observer API