Re: [ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
On Wed, 2020-03-11 at 20:01 +0200, Roman Hershkovich wrote: > But colocation of dbprobe won't pull trigger of webserver ? Or > because that it is below in order - it will just restart services ? I'm not sure what you mean. Resource failures don't cause node fencing unless you explicitly ask for it with on-fail=fence. Resource failures don't cause failover to another node unless migration-threshold is set for the resource (or it fails a million times). If you want the db monitor failure to cause the web server to restart, order the web server after the db monitor. Otherwise, the db monitor failure won't have any effect on the web server. > On Wed, Mar 11, 2020, 18:41 Ken Gaillot wrote: > > On Wed, 2020-03-11 at 16:08 +0200, Roman Hershkovich wrote: > > > Great, thank you very much for explanation. Regarding returning > > error > > > - i did not knew. > > > So, basically i can have a service, that will probe for master > > DB, in > > > case of its transfer - service will update /etc/hosts and return > > > error, which will be caught by pcs and it will restart whole > > > dependent set ? Sounds good. > > > But how i can do 2 "main resources" ? I have webserver AND > > > db_monitor. In case of failure of webserver - should all start on > > > node b, but in case of DB change - only underlying resources ... > > > Should i make webserver outside of set? > > > > If you want the webserver to move to another node after a single > > failure (of the webserver itself), set its migration-threshold to > > 1. If > > you want other resources to move with it, colocate them with the > > webserver. > > > > The db monitor won't affect that -- if the db monitor fails, > > anything > > ordered after it will restart. > > > > > On Wed, Mar 11, 2020 at 3:57 PM Ken Gaillot > > > wrote: > > > > On Wed, 2020-03-11 at 02:27 +0200, Roman Hershkovich wrote: > > > > > 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) > > > > > > > > That sounds fine, but I'd trigger the restart by returning an > > error > > > > code from the db-monitoring script, rather than directly > > attempt to > > > > restart the resources via pcs. If you order the other resources > > > > after > > > > the db-monitoring script, pacemaker will automatically restart > > them > > > > when the db-monitoring script returns an error. > > > > > > > > > In addition - i thought maybe bringing PAF here could be > > useful - > > > > but > > > > > this is even more complex ... > > > > > > > > If bringing the db into the cluster is a possibility, that > > would > > > > probably be more reliable, with a quicker response too. > > > > > > > > In that case you would simply order the dependent resources > > after > > > > the > > > > database master promotion. pcs example: pcs constraint order > > > > promote > > > > DB-RSC then start DEPENDENT-RSC > > > > > > > > > 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
Re: [ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
But colocation of dbprobe won't pull trigger of webserver ? Or because that it is below in order - it will just restart services ? On Wed, Mar 11, 2020, 18:41 Ken Gaillot wrote: > On Wed, 2020-03-11 at 16:08 +0200, Roman Hershkovich wrote: > > Great, thank you very much for explanation. Regarding returning error > > - i did not knew. > > So, basically i can have a service, that will probe for master DB, in > > case of its transfer - service will update /etc/hosts and return > > error, which will be caught by pcs and it will restart whole > > dependent set ? Sounds good. > > But how i can do 2 "main resources" ? I have webserver AND > > db_monitor. In case of failure of webserver - should all start on > > node b, but in case of DB change - only underlying resources ... > > Should i make webserver outside of set? > > If you want the webserver to move to another node after a single > failure (of the webserver itself), set its migration-threshold to 1. If > you want other resources to move with it, colocate them with the > webserver. > > The db monitor won't affect that -- if the db monitor fails, anything > ordered after it will restart. > > > On Wed, Mar 11, 2020 at 3:57 PM Ken Gaillot > > wrote: > > > On Wed, 2020-03-11 at 02:27 +0200, Roman Hershkovich wrote: > > > > 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) > > > > > > That sounds fine, but I'd trigger the restart by returning an error > > > code from the db-monitoring script, rather than directly attempt to > > > restart the resources via pcs. If you order the other resources > > > after > > > the db-monitoring script, pacemaker will automatically restart them > > > when the db-monitoring script returns an error. > > > > > > > In addition - i thought maybe bringing PAF here could be useful - > > > but > > > > this is even more complex ... > > > > > > If bringing the db into the cluster is a possibility, that would > > > probably be more reliable, with a quicker response too. > > > > > > In that case you would simply order the dependent resources after > > > the > > > database master promotion. pcs example: pcs constraint order > > > promote > > > DB-RSC then start DEPENDENT-RSC > > > > > > > On Tue, Mar 10, 2020 at 10:28 PM Ken Gaillot > > > > > > > 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 > > >
Re: [ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
On Wed, 2020-03-11 at 16:08 +0200, Roman Hershkovich wrote: > Great, thank you very much for explanation. Regarding returning error > - i did not knew. > So, basically i can have a service, that will probe for master DB, in > case of its transfer - service will update /etc/hosts and return > error, which will be caught by pcs and it will restart whole > dependent set ? Sounds good. > But how i can do 2 "main resources" ? I have webserver AND > db_monitor. In case of failure of webserver - should all start on > node b, but in case of DB change - only underlying resources ... > Should i make webserver outside of set? If you want the webserver to move to another node after a single failure (of the webserver itself), set its migration-threshold to 1. If you want other resources to move with it, colocate them with the webserver. The db monitor won't affect that -- if the db monitor fails, anything ordered after it will restart. > On Wed, Mar 11, 2020 at 3:57 PM Ken Gaillot > wrote: > > On Wed, 2020-03-11 at 02:27 +0200, Roman Hershkovich wrote: > > > 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) > > > > That sounds fine, but I'd trigger the restart by returning an error > > code from the db-monitoring script, rather than directly attempt to > > restart the resources via pcs. If you order the other resources > > after > > the db-monitoring script, pacemaker will automatically restart them > > when the db-monitoring script returns an error. > > > > > In addition - i thought maybe bringing PAF here could be useful - > > but > > > this is even more complex ... > > > > If bringing the db into the cluster is a possibility, that would > > probably be more reliable, with a quicker response too. > > > > In that case you would simply order the dependent resources after > > the > > database master promotion. pcs example: pcs constraint order > > promote > > DB-RSC then start DEPENDENT-RSC > > > > > On Tue, Mar 10, 2020 at 10:28 PM Ken Gaillot > > > > > 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
Re: [ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
Great, thank you very much for explanation. Regarding returning error - i did not knew. So, basically i can have a service, that will probe for master DB, in case of its transfer - service will update /etc/hosts and return error, which will be caught by pcs and it will restart whole dependent set ? Sounds good. But how i can do 2 "main resources" ? I have webserver AND db_monitor. In case of failure of webserver - should all start on node b, but in case of DB change - only underlying resources ... Should i make webserver outside of set? On Wed, Mar 11, 2020 at 3:57 PM Ken Gaillot wrote: > On Wed, 2020-03-11 at 02:27 +0200, Roman Hershkovich wrote: > > 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) > > That sounds fine, but I'd trigger the restart by returning an error > code from the db-monitoring script, rather than directly attempt to > restart the resources via pcs. If you order the other resources after > the db-monitoring script, pacemaker will automatically restart them > when the db-monitoring script returns an error. > > > In addition - i thought maybe bringing PAF here could be useful - but > > this is even more complex ... > > If bringing the db into the cluster is a possibility, that would > probably be more reliable, with a quicker response too. > > In that case you would simply order the dependent resources after the > database master promotion. pcs example: pcs constraint order promote > DB-RSC then start DEPENDENT-RSC > > > On Tue, Mar 10, 2020 at 10:28 PM Ken Gaillot > > 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 > -- > Ken Gaillot > > ___ > Manage your subscription: > https://lists.clusterlabs.org/mailman/listinfo/users > > ClusterLabs home: https://www.clusterlabs.org/ > ___ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
Re: [ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
On Wed, 2020-03-11 at 02:27 +0200, Roman Hershkovich wrote: > 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) That sounds fine, but I'd trigger the restart by returning an error code from the db-monitoring script, rather than directly attempt to restart the resources via pcs. If you order the other resources after the db-monitoring script, pacemaker will automatically restart them when the db-monitoring script returns an error. > In addition - i thought maybe bringing PAF here could be useful - but > this is even more complex ... If bringing the db into the cluster is a possibility, that would probably be more reliable, with a quicker response too. In that case you would simply order the dependent resources after the database master promotion. pcs example: pcs constraint order promote DB-RSC then start DEPENDENT-RSC > On Tue, Mar 10, 2020 at 10:28 PM Ken Gaillot > 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 -- Ken Gaillot ___ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
Re: [ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
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 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 > > ___ > Manage your subscription: > https://lists.clusterlabs.org/mailman/listinfo/users > > ClusterLabs home: https://www.clusterlabs.org/ > ___ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
Re: [ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
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 ___ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
Re: [ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
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 ? On Tue, Mar 10, 2020 at 8:42 PM Strahil Nikolov 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/
[ClusterLabs] I want to have some resource monitored and based on that make an acton. Is it possible?
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) ? ___ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
