[ClusterLabs] Resolving cart before the horse with mounted filesystems.

[Matthew Schumacher]

On 4/30/21 11:51 AM, Ken Gaillot wrote:
> On Fri, 2021-04-30 at 16:20 +0000, Strahil Nikolov wrote:
>> Ken ment yo use 'Filesystem' resourse for mounting that NFS server
>> and then clone that resource.
>>
>> Best Regards,
>> Strahil Nikolov

I tried my best to explain in the original post, but like much of this 
stuff, it's complex and hard to explain.  I'll try again.

I have a singular NFS server that is a resource in my cluster.  It can 
run on any node.

Each node needs to mount this NFS server before VirtualDomain resources 
can start.

I run into cart before the horse because if I mount NFS before starting 
pacemaker on a booting node, it works fine if that node is connecting to 
a running cluster as the NFS server is already running, but if that node 
is the first node starting a cold cluster, it doesn't work because the 
mount fails as we haven't started pacemaker yet which brings up the NFS 
server.  When pacemaker starts, it starts the VirtualDomain resources, 
which fail because the NFS mount isn't mounted.

The idea would be make the NFS mount on each node a resource using 
Filesystem and make VirtualDomain depend on that, but then the 
dependency would need to change based on which node VirtualDomain runs 
on as it would depend on node1-Filesystem if VirtualDomain runs on node1 
and node2-Filesystem if VirtualDomain runs on node2.

I'm currently working on understanding and implementing this suggestion 
from Andrei:

Which is exactly what clones are for. Clone NFS mount and order
VirtualDomain after clone. Just do not forget to set interleave=true so
VirtualDomain considers only local clone instance.

It sounds like what I want to do.

Matt