Yes. I have only 1 APP active at same time, and so I want this app to be restarted whenever DB changes. Another one is a "standby" APP, where all resources are shut. So i thought about adding some "service" script, which will probe a DB , and in case if it finds a CHANGE - will trigger pcs to reload a set of resources, where one of resource would be a systemctl file, which will continue to run a script, so in case of next change of DB - it will restart APP set again. Is it sounds reasonable? (i don't care of errors. I mean - i do, i want to log, but i'm ok to see them)
In addition - i thought maybe bringing PAF here could be useful - but this is even more complex ... On Tue, Mar 10, 2020 at 10:28 PM Ken Gaillot <kgail...@redhat.com> wrote: > On Tue, 2020-03-10 at 21:03 +0200, Roman Hershkovich wrote: > > DB servers are not in PCS cluster. Basically you say that i need to > > add them to PCS cluster and then start them? but in case if DB1 fails > > - DB2 autopromoted and not required start of service again> > > > > Regarding colocation rule - i'm kind of missing logic how it works - > > how i can "colocate" 1 of 2 APP servers to be around a master DB ? > > If I understand correctly, what you want is that both apps are > restarted if the master changes? > > I'm thinking you'll need a custom OCF agent for the app servers. The > monitor action, in addition to checking the app's status, could also > check which db is master, and return an error if it's changed since the > last monitor. (The start action would have to record the initial > master.) Pacemaker will restart the app to recover from the error. > > That is a little hacky because you'll have errors in the status every > time the master moves, but maybe that's worth knowing in your situation > anyway. > > > On Tue, Mar 10, 2020 at 8:42 PM Strahil Nikolov < > > hunter86...@yahoo.com> wrote: > > > On March 10, 2020 7:31:27 PM GMT+02:00, Roman Hershkovich < > > > war...@gmail.com> wrote: > > > >I have 2 DB servers (master/slave with replica) and 2 APP servers. > > > >2 APP servers managed by pacemaker (active/passive) , but i want > > > also > > > >to > > > >monitor "which DB is master". I can't use VIP (which could be > > > sticked > > > >on > > > >master DB) - it is very limited virtual environment. > > > > > > > >Is it possible to create a rule or some other scenario, so in case > > > if > > > >master moved - pacemaker will restart APP (app does not support > > > >failover) ? > > > > > > Hi Roman, > > > > > > If you set an order rule that starts first the master and then > > > the app, during a failover the app will be stoped and once the > > > master is switched (slave is promoted) the app will be started > > > again. > > > > > > Also you can consider a colocation rule that all apps are > > > started where the master DB is running - so the lattency will > > > be minimal. > > > > > > Best Regards, > > > Strahil Nikolov > > > > _______________________________________________ > > Manage your subscription: > > https://lists.clusterlabs.org/mailman/listinfo/users > > > > ClusterLabs home: https://www.clusterlabs.org/ > -- > Ken Gaillot <kgail...@redhat.com> > > _______________________________________________ > Manage your subscription: > https://lists.clusterlabs.org/mailman/listinfo/users > > ClusterLabs home: https://www.clusterlabs.org/ >
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