[ClusterLabs] Antw: [EXT] Re: Serialize and symmetrical=true does not work together

[Ken Gaillot]

On Tue, 2020-03-17 at 07:45 +0100, Ulrich Windl wrote:
> > > > Ken Gaillot <kgaillot at redhat.com> schrieb am 17.03.2020 um
> > > > 00:58 in
> 
> Nachricht
> <1227_1584403147_5E7012CB_1227_2106_1_3a13cd73f8738e6967d6b1c399e994a
> 1155495c3.c
> mel at redhat.com>:
> > It has always been the case that symmetrical=true was ignored (with
> > a
> > warning) for serialized constraints; the only recent change was
> > making
> > false the default so the warning wouldn't be displayed.
> > 
> > If you want the services to start and stop in a particular order,
> > you
> > don't want a serialized constraint, just a regular order
> > constraint. A
> > serialized constraint merely says that the actions can't be done at
> > the
> > same time, either one may be done first.
> > 
> > If you have a serialized constraint saying the resources can't
> > start at
> > the same time, and want that to apply to stops as well, then you
> > can
> > create a second serialized constraint explicitly specifying stop as
> > the
> > action to be ordered.
> 
> Maybe a simple, but realistic example would help to understand.

Good idea ...

1. You have two databases that hog a lot of resources on start-up. You
don't care which one starts first, but you don't want them starting at
the same time because it slows everything down too much.

   -> use an order constraint with kind="Serialize". other actions
(including stop) are unaffected

2. Same, but stopping slows everything down too.

   -> use two order constraints with kind="Serialize", one with
first/then action = start (or let them default) and the other with
first/then action = stop

3. Database B must be started after database A, and B must be stopped
before A can be stopped.

   -> use a normal "A then B" order constraint

> > 
> > On Mon, 2020‑03‑16 at 19:41 +0530, Dileep V Nair wrote:
> > > Hi,
> > > 
> > > I have pacemaker clusters which were working fine with Serialize
> > > and
> > > symmetrical=true together. After an upgrade, I see that Serialize
> > > does not work with symmetrical=true. How do I make sure the
> > > resources
> > > in Serialize stop in reverse order of start ? All the clusters
> > > are
> > > already in production. Please help.
> > > 
> > > Thanks & Regards
> > > 
> > > Dileep Nair
> > > Squad Lead ‑ SAP Base 
> > > Togaf Certified Enterprise Architect
> > > IBM Services for Managed Applications
> > > +91 98450 22258 Mobile
> > > dilenair at in.ibm.com 
> > > 
> > > IBM Services
> > > 
> > > _______________________________________________
> > > Manage your subscription:
> > > https://lists.clusterlabs.org/mailman/listinfo/users 
> > > 
> > > ClusterLabs home: https://www.clusterlabs.org/ 
> > 
> > ‑‑ 
> > Ken Gaillot <kgaillot at redhat.com>
> > 
> > _______________________________________________
> > 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/
-- 
Ken Gaillot <kgaillot at redhat.com>