[hobbit] Advice on how to handle HA monitoring

[Haertig, David F (Dave)]

I do this with a custom monitoring script (I don't use the standard
Hobbit 'procs' test).

There should be something you can check via script that tells you if a
server is primary or not.  In my case, a database filesystem is mounting
on the primary but not on the secondary.  So my script uses 'df' to look
for that filesystem.  You could use 'mount' as well.  If that database
filesystem is mounted the script does the normal test for processes and
reports red/green.  But if it's not mounted, the script reports a clear
condition. 

-----Original Message-----
From: Charles Jones [mailto:jonescr at cisco.com] 
Sent: Friday, September 21, 2007 1:12 PM
To: hobbit at hswn.dk
Subject: [hobbit] Advice on how to handle HA monitoring

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.

Any ideas? :)

-Charles

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