[dm-devel] [PATCH 09/13] multipathd: Implement systemd watchdog integration

[Hannes Reinecke]

On 11/25/2013 08:50 AM, Hannes Reinecke wrote:
> On 11/22/2013 11:17 PM, Benjamin Marzinski wrote:
[ .. ]
>> I'm not asking for systemd to actually shut down multipathd.  In a
>> production setup, killing multipathd because it had a temporary stall
>> seems like bad default behavior.  I haven't looked at the systemd
>> watchdog code to know if this is possible, but ideally, multipathd would
>> be able to just start sending watchdog notifications again, and be able
>> to continue on with just a message in the logs recording the timeout.
>>
> Not stopping. Restarting.
> The whole point of the watchdog code is to take some action if the
> watchdog messages fail.
> We should aim for
> a) make the watchdog interval the longest interval we're prepared to
>     checkerloop to complete (hence the patch to measure the elapsed
>     time per loop iteration)
> b) have systemd restart multipathd whenever the watchdog triggers,
>     as then we're sure we can't recover from this.
>
> That should cover your sentiment, right?
>
>> I realize that there is a benefit to letting people know that there was
>> a problem, but the way it's appearing now, it will be pretty confusing to
>> the sysadmin who sees that, and filling up the logs with notification
>> rejections is pretty annoying.
>>
> Yeah, correct. We should be using the 'restart' flag in the service
> file. I did not do this as the patch went into systemd only
> recently, and one would need to figure out how to treat
> installations where an older systemd version is running.
>
And it also looks as if we'd be tripping over RH bug#982379, where
the watchdog fails to shutdown a process properly.
Which apparently is fixed in 206.
So we'd need a recent systemd for that to work properly.

I'm _quite_ sure there are errors in earlier versions, where the
watchdog feature just causes a new process to be started, without
terminating the old one. _Very_ annoying.

I'll retest with latest systemd. And make the watchdog feature
selective on the systemd version.

Cheers,

Hannes