On Friday 21 September 2007 21:11:42 Charles Jones wrote:
We have 2 hosts, HostA and HostB. They are part of an HA cluster via HP
ServiceGuard. There is a virtual IP and DNS name of "virtual" that
automatically goes to whichever of HostA and HostB is the primary at the
time.
I am currently monitoring both HostA and HostB via Hobbit. Currently
HostA is the primary, and I am doing various PROC checks. Currently on
HostB, I am not doing process checks.
My problem is, how do I smoothly handle a failover scenario (HostB
becoming the primary)? When a failover occurs, all of the procs on
HostA are stopped (either by the server crashing, or manualy by
ServiceGuard), and the same procs are started up on HostB.
I'm trying to think of ways to monitor both hosts, but only monitor
procs on the one that is primary. So far the best I can come up with is
to run the hobbit clients in local mode, and maybe have the ServiceGuard
scripts swap out the config files and restart the Hobbit clients when
there is a failover. That would probably work, BUT in this case the
Hobbit homdir is also the same (SAN mount) on both machines, so moving
or editing a file on one does the same on the other :(
Simply shutting down the hobbit client on the non-primary is not an
option, as then it would no longer be monitored at all.
What I do is to do all the infrastructure tests on both nodes, the procs
checks check only for the cluster intrastructure (besides local processes
like say syslog), then a check using the cluster software on both nodes, and
finally monitor the network services (and only them) on the clustered
service's IP.
And, there are a few reasons I avoid installing software on the SAN, this is
one of them ... (the other is that if you screw up upgrading your clustered
software, you have an outage, whereas if it's installed locally on each box,
you could just fail back ... or in most cases the cluster middleware would
have done it already).
Regards,
Buchan