Convergence Observer Specification

This spec is a child spec of convergence.

specs bp convergence-observer
Change-Id: Id309bb1c847b976f0ba4a69ee99f3b3ed90ff356

specs/convergence-observer.rst

@@ -0,0 +1,73 @@
+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+======================
+ Convergence Observer
+======================
+
+https://blueprints.launchpad.net/heat/+spec/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`.
+
+Alternatives
+------------
+
+-
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Work should be spread between all developers as much as possible to help
+spread awareness of how things work.
+
+Milestones
+----------
+
+Target Milestone for completion:
+  Juno-2
+
+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
+
+Dependencies
+============
+
+-