[openstack-dev] [TripleO][Heat] using convergence_engine to deploy overcloud stack

Rabi Mishra ramishra at redhat.com
Wed Aug 9 10:49:30 UTC 2017

On Wed, Aug 9, 2017 at 1:41 PM, Smigielski, Radoslaw (Nokia - IE) <
radoslaw.smigielski at nokia.com> wrote:

> Hi there!
>    I have a question about heat "convergence_engine" option, it's present
> in heat config since quite a long time but still not enabled.
Well, convergence is enabled by default in heat since newton. However,
Tripleo does not use it yet, as convergence engine memory usage is higher
than that of legacy engine.

There has been number of optimizations in the last two cycles to improve
that situation. However, AFAIK, when using a single node undercloud, memory
usage would always be more with convergence.

I think there are plans for Tripleo to move to convergence in Queens as
discussed in this ML thread.


And I am wondering if anyone has tried enabled it and deploy overcloud? I
> did it myself and it seems to be working.
> The main reason why I am looking at this options are problems with scaling
> out, adding computes, replacing failed controllers on setups with 50+
> computes and number of nested stack 1000+.

You've to probably scale out undercloud heat to get most of the benefits of
convergence that comes with the distributed architecture.

> Is there any reason what holds Heat switch to convergence architecture?
> _________________________
> *Radosław Śmigielski*
> Nokia CBIS R&D
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Rabi Misra
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