Hi Steven et al.
2014-04-15 17:01 GMT+02:00 Steven Dake <sd...@redhat.com>: > >> Qiming, > > If you read my original post on this thread, it outlines the current > heat-core thinking, which is to reduce the scope of this resource from the > Heat resources since it describes a workflow rather then an orchestrated > thing (a Noun). > > A good framework for HA already exists for HA in the HARestarter resource. > It incorporates HA escalation, which is a critical feature of any HA > system. The fundamental problem with HARestarter is that is in the wrong > project. > > Long term, HA, if desired, should be part of taskflow, though, because its > a verb, and verbs don't belong as heat orchestrated resources. > > How we get from here to there is left as an exercise to the reader ;-) > > Regards > -steve > > >From my POV, I can consider that the HA feature would be something like AutoScaling in Heat, meaning it would involve multiple stakeholders : - Ceilometer for aggregating metrics from hosts and raising an Alarm which will trigger a WebHook corresponding to the faulty resource - Heat for declaring all HA policies within a template and creating appropriate Ceilometer Alarms - the service behind the Webhook for executing the remediation actions (Heat) which would call the appropriate services (eg. Nova) - eg. Nova to perform live migrations of the instances if possible, or evacuate I don't know if Taskflow would be necessary for doing the logic here, that's more likely a placement issue than a workflow issue, as it requires to schedule new resources but can only be made on a per-resource basis (Nova instances, Cinder volumes, etc.). Taskflow would here be helpful for having a all-or-one logic in case of the migration untl the scheduling would be holistic. Of course, in a far far away galaxy, we could consider having one global Scheduler for placement decisions that Heat could query for live migrating resources, but I'm still dreaming... -Sylvain
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