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Hi,

The use case you describe is already supported, but not yet via nova notifications, see these templates (one as previously linked by Angus);

https://github.com/openstack/heat-templates/blob/master/cfn/WordPress_Single_Instance_With_HA.template https://github.com/openstack/heat-templates/blob/master/cfn/WordPress_Single_Instance_With_IHA.template

The first template restarts the httpd service if it is not running, then rebuilds the instance if this fails more than a defined number of times.

The second template sends a heartbeat message from the instance, such that it is rebuilt if the heartbeat timeout is exceeded.

Clearly using nova notifications to do this will be better long-term, but this is the solution we have today (in grizzly).

For havana, as previously outlined, things are set to change considerably - the watch-ceilometer BP is tracking the integration with the new-for-havana ceilometer alarms functionality. This work includes the "webhook" mechanism described, it does not yet exist, we're still working out how to implement it.

I would suggest not pursuing the option of implementing this all in heat-engine, as we plan to remove the periodic/watchrule functionality when the ceilometer integration is completed.

IMO your effort is likely to be better spent ensuring that the new ceilometer alarms functionality is capable of alarming in the scenarios where you wish to trigger heat actions from, then when we complete the watch-ceilometer work you should have a solution that works for you in havana.