[Openstack-operators] [heat] convergence and / or instance autohealing

Justin Cattle j at ocado.com
Wed Apr 19 11:08:00 UTC 2017


I've been looking around various docs and wiki pages and code repos, and
I'm finding it hard to pin down the current possibilities for two related

   1. Heat stacks that maintain a minimum number of instances [ if an
   instance crashes, goes into an error state, or the kvm process dies etc ].
   2. Auto-healing instances [ A pet type instance that is re-spawned if it
   dies for some reason ].

I'm mostly interested in [1] - I just mention [2] it as an option that is
related to [1].

Googling around, a lot of talk around heat's new convergence engine
suggested it was going to enable [1].  However, I can't find any concrete
info on how you would set that up within a heat template, and what else is
required to be configured at the openstack service level.

Just enabling the convergence engine in heat on Mitaka, I don't see any
extra python processing that might be "observers".  Is it only possible in
later versions ?

I have found these recently added hot templates:


However, they seem to be using Zaqar and Mistral to achieve the goal of [1].

So, can convergence achieve [1], and if so how ?  Or is using Zaqar and
Mistral my main option right now ?



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