On Feb 7, 2008 10:08 AM, Lino Moragon <[EMAIL PROTECTED]> wrote:
> Hi list,
> I'm running a HA 2 node active / passive cluster with drbd and mysql.
> I was told about the ocf monitoring function of the yet available mysql
> ocf script.
The base monitor function in the mysql RA does only a check if there
is a process with the PID of your mysql instance running.
> Could you tell me the advantages or disadvantages of implementing this
> monitoring function?
We have a quite similar cluster in our production environment and I
encountered no problems with a "deeper" mysql check. I installed a
small test db (the 'City' db from the mysql site) that's exclusive for
heartbeat's monitor selects so no table locking problems should occur.
Of course you should not run out of available mysql connections and
choose timeout values appropriate to your system load.
A monitor example:
<op id="op_DB_community-monitor" interval="10s" name="monitor"
timeout="10s" start_delay="30s">
<instance_attributes id="ia_op_DB_community-monitor">
<attributes>
<nvpair id="op_DB_community-monitor-check_level"
name="OCF_CHECK_LEVEL" value="10"/>
</attributes>
</instance_attributes>
</op>
> I mean surely it does have benefits, but what if I my php
> webapplications e.g. generate too much load, too large and complex
> queries and the timeout value exceeds?
> Then the server would restart or failover and then that would repeat
> itself on and on and my ha-cluster wouldn't be a hacluster anymore.
> Have you any experience what possible things could happen to a mysql
> server and what would be the reasons for hang-up, crash, etc...?
> Problem is, I can't estimate the load or amount of queries the
> application will generate, as I don't have much experience in this field
> and the DBs will grow over time.
> Should I implement ocf monitoring or rather not?
I'm convinced you should ;-)
Regards,
Andreas
>
> I'm very thankful for any advice or hints about this matter, where to
> get more information, or personal experiences with the stability of
> mysql servers.
> Thanks
> Lino
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>
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