I've been working on this spec for TripleO: https://review.openstack.org/#/c/431745/
which allows users to selectively disable Heat deployment resources for a given server (or server in the case of a *DeloymentGroup resource). Some of the main use cases in TripleO for such a feature are scaling out compute nodes where you do not need to rerun Puppet (or make any changes at all) on non-compute nodes, or to exclude nodes from hanging a stack-update if you know they are unreachable or degraded for some reason. There are others, but those are 2 of the major use cases. I started by taking an approach that would be specific to TripleO. Basically mapping all the deployment resources to a nested stack containing the logic to selectively disable servers from the deployment (using yaql) based on a provided parameter value. Here's the main patch: https://review.openstack.org/#/c/442681/ After considering that complexity, particularly the yaql expression, I'm wondering if it would be better to add this support natively to Heat. I was looking at the restricted_actions key in the resource_registry and was thinking this might be a reasonable place to add such support. It would require some changes to how restricted_actions work. One change would be a method for specifying that restricted_actions should not fail the stack operation if an action would have otherwise been triggered. Currently the behavior is to raise an exception and mark the stack failed if an action needs to be taken but has been marked restricted. That would need to be tweaked to allow specifying that that we don't want the stack to fail. One thought would be to change the allowed values of restricted_actions to: replace_fail replace_ignore update_fail update_ignore replace update where replace and update were synonyms for replace_fail/update_fail to maintain backwards compatibility. Another change would be to add logic to the Deployment resources themselves to consider if any restricted_actions have been set on an Server resources before triggering an updated deployment for a given server. It also might be nice to allow specifying restricted_actions on the server's name property (which typically is the hostname) instead of having to use the resource name. The reason being is that it is not really feasibly to expect operators/users to have to represent the full nested_stack structure in their resource_registry. They would have to query and record nested_stack names just to refer to a given server resource. Each ResourceGroup nested stack would be have to be individually represented, etc. Unless there is another way I'm overlooking. Whether or not the restricted_actions approach is taken, is Heat interested in this functionality natively? I think it would make for a much cleaner implementation than something TripleO specific. I can work on a Heat spec if there's interest, though I'd like to get some early feedback. Thanks. -- -- James Slagle -- __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev