[openstack-dev] [Heat] HOT software configuration refined after design summit discussions

Steve Baker sbaker at redhat.com
Tue Nov 19 21:06:21 UTC 2013

On 11/20/2013 09:50 AM, Clint Byrum wrote:
> Excerpts from Steve Baker's message of 2013-11-18 12:52:04 -0800:
>> Regarding apply_config/remove_config, if a SoftwareApplier resource is
>> deleted it should trigger any remove_config and wait for the server to
>> acknowledge when that is complete. This allows for any
>> evacuation/deregistering workloads to be executed.
> I'm a little worried about the road that leads us down. Most configuration
> software defines forward progress only. Meaning, if you want something
> not there, you don't remove it from your assertions, you assert that it
> is not there.
> The reason this is different than the way we operate with resources is
> that resources are all under Heat's direct control via well defined
> APIs. In-instance things, however, will be indirectly controlled. So I
> feel like focusing on a "diff" mechanism for user-deployed tools may be
> unnecessary and might confuse. I'd much rather have a "converge"
> mechanism for the users to focus on.
A specific use-case I'm trying to address here is tripleo doing an
update-replace on a nova compute node. The remove_config contains the
workload to evacuate VMs and signal heat when the node is ready to be
shut down. This is more involved than just "uninstall the things".

Could you outline in some more detail how you think this could be done?

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