Hi All, As part of Liberty spec [1] was approved with the conclusion that nova.services data be stored and managed by respective driver backend that is selected by the CONF.servicegroup_driver (which can be DB/Zookeeper/Memcache).
When this spec was proposed again for Mitaka[3], the idea that has come up is that the nova.services data will remain in nova database itself and the servicegroup zookeeper, memcache drivers be used solely for liveliness/up/down ness of the service. The idea being using the best of both worlds and few operations for example getting min/max for a service id can be quicker when done a query in DB in comparison to ZK/Memcache backends. But ZK driver is worthwhile for state management as it minimizes the burden on nova db to store the additional *periodic* (depending on service_down_time) liveliness information. Please note [4] depends on [3] and a conclusion on [3] can pave a way forward for [4] (similarly [1] was a dependency for [2]). A detail document [5] encompassing all the possible options by having different permutation of various drivers (db/zk/mc). Once we have a conclusion on one of the approach proposed in [5] will update spec [3] to reflect these changes. So in short *Accepted in Liberty [1] [2] :* [1] Services information be stored in respective backend configured by CONF.servicegroup_driver and all the interfaces which plan to access service information go through servicegroup layer. [2] Add tooz specific drivers e.g. replace existing nova servicegroup zookeeper driver with a new zookeeper driver backed by Tooz zookeeper driver. *Proposal for Mitaka [3][4] :* [3] Services information be stored in nova.services (nova database) and liveliness information be managed by CONF.servicegroup_driver (DB/Zookeeper/Memcache) [4] Stick to what is accepted for #2. Just that the scope will be decided based on whether we go with #1 (as accepted for Liberty) or #3 (what is proposed for Mitaka) - Vilobh [1] Servicegroup foundational refactoring for Control Plane *(Liberty)* - https://review.openstack.org/#/c/190322/ [2] Add tooz service group driver* (Liberty)* - https://review.openstack.org/#/c/138607/ [3] Servicegroup foundational refactoring for Control Plane *(Mitaka)* - https://review.openstack.org/#/c/222423/ [4] Add tooz service group driver *(Mitaka) *- https://review.openstack.org/#/c/222422/ [5] *Various options and there impact* : https://etherpad.openstack.org/p/servicegroup-refactoring
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