[ClusterLabs] ocf:lvm2:VolumeGroup Probe Issue

[Ken Gaillot]

On 11/08/2016 10:37 AM, Marc Smith wrote:
> Hi,
> 
> First, I realize ocf:lvm2:VolumeGroup comes from the LVM2 package and
> not resource-agents, but I'm hoping someone on this list is familiar
> with this RA and can provide some insight.
> 
> In my cluster configuration, I'm using ocf:lvm2:VolumeGroup to manage
> my LVM VG's, and I'm using the cluster to manage DLM and CLVM. I have
> my constraints in place and everything seems to be working mostly,
> except I'm hitting a glitch with ocf:lvm2:VolumeGroup and the initial
> probe operation.
> 
> On startup, a probe operation (monitor) is issued for all of the
> resources, but ocf:lvm2:VolumeGroup is returning OCF_ERR_GENERIC in
> VolumeGroup_status() (via VolumeGroup_monitor()) since clvmd hasn't
> started yet... this line in VolumeGroup_status() is the trouble:
> 
> VGOUT=`vgdisplay -v $OCF_RESKEY_volgrpname 2>&1` || exit $OCF_ERR_GENERIC
> 
> When clvmd is not running, 'vgdisplay -v name' will always return
> something like this:
> 
> --snip--
>   connect() failed on local socket: No such file or directory
>   Internal cluster locking initialisation failed.
>   WARNING: Falling back to local file-based locking.
>   Volume Groups with the clustered attribute will be inaccessible.
>     VG name on command line not found in list of VGs: biggie
>   Volume group "biggie" not found
>   Cannot process volume group biggie
> --snip--
> 
> And exits with a status of 5. So, my question is, do I patch the RA?
> Or is there some cluster constraint I can add so a probe/monitor
> operation isn't performed for the VolumeGroup resource until CLVM has
> been started?

Ordered probes is a desired feature for Pacemaker, but the
implementation is much trickier than it appears at first glance, so
there's no timeline for when it might arrive.

In the meantime, patching the RA to exit with "not running" in this
situation is probably the best workaround. There is a library function
ocf_is_probe you can use to avoid messing with "real" monitors.

> Any other advice? Is ocf:heartbeat:LVM or ocf:lvm2:VolumeGroup the
> more popular RA for managing LVM VG's? Any comments from other users
> on experiences using either (good, bad)? Both appear to achieve the
> same function, just a bit differently.
> 
> 
> Thanks,
> 
> Marc