On 05/20/2016 08:39 AM, Ulrich Windl wrote: >>>> Jehan-Guillaume de Rorthais <j...@dalibo.com> schrieb am 19.05.2016 um >>>> 21:29 in > Nachricht <20160519212947.6cc0fd7b@firost>: > [...] >> I was thinking of a use case where a graceful demote or stop action failed >> multiple times and to give a chance to the RA to choose another method to >> stop >> the resource before it requires a migration. As instance, PostgreSQL has 3 >> different kind of stop, the last one being not graceful, but still better >> than >> a kill -9. > For example the Xen RA tries a clean shutdown with a timeout of about 2/3 of > the timeout; it it fails it shuts the VM down the hard way. > > I don't know Postgres in detail, but I could imagine a three step approach: > 1) Shutdown after current operations have finished > 2) Shutdown regardless of pending operations (doing rollbacks) > 3) Shutdown the hard way, requiring recovery on the next start (I think in > Oracle this is called a "shutdown abort") > > Depending on the scenario one may start at step 2) > > [...] > I think RAs should not rely on "stop" being called multiple times for a > resource to be stopped.
I see a couple of positive points in having something inside pacemaker that helps the RAs escalating their stop strategy: - this way you have the same logging for all RAs - done within the RA it would look different with each of them - timeout-retry stuff is potentially prone to not being implemented properly - like this you have a proven implementation within pacemaker - keeps logic within RA simpler and guides implementation in a certain direction that makes them look more similar to each other making it easier to understand an RA you haven't seen before Of course there are basically two approaches to achieve this: - give some global or per resource view of pacemaker to the RA and leave it to the RA to act in a responsible manner (like telling the RA that there are x stop-retries to come) - handle the escalation withing pacemaker and already tell the RA what you expect it to do like requesting a graceful / hard / emergency or however you would call it stop > > Regards, > Ulrich > > > > > _______________________________________________ > Users mailing list: Users@clusterlabs.org > http://clusterlabs.org/mailman/listinfo/users > > Project Home: http://www.clusterlabs.org > Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf > Bugs: http://bugs.clusterlabs.org _______________________________________________ Users mailing list: Users@clusterlabs.org http://clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
