Comment 4 for bug 1598946

The reason why this cannot be considered as a bug is because there as many outstanding issues that would have to be treated in the decision engine for it to be HA-ready.

The first one is indeed the database sync that would have to be handled across 2+ decision engine processes.

Once this phase is correctly handled, we would also need to make the whole strategy execution become stateless, which is not currently the case:

- How do we handle continuous audits across multiple nodes given that they are background tasks?
- If we instantiate multiple, that implies we have make N times more queries that would hit Nova, Neutron and so on as we build our data models in-memory. Is it OK for us to increase the network I/O ? Is there something we need to do to mitigate this?

If we have a decision engine that is HA-ready, that would also mean that we have to make the Watcher Applier HA-ready in order to be able to cope with the expected increase of action plans to execute:

- How do we handle the execution of action plans across multiple processes?
- ...

My point here is to give you an insight to some of the questions that need to be answered in order for Watcher to fully support HA. However, the added value at the moment is quite minimal given the fact that Watcher isn't necessary to the good functioning of an OpenStack infrastructure. This is the reason my I would argue we shouldn't push for this (at least for now) even though this may become a priority in the future.