[ClusterLabs] Start resource only if another resource is stopped

[Andrei Borzenkov]

On 17.08.2022 16:58, Miro Igov wrote:
> As you guessed i am using crm res stop nfs_export_1. 
> I tried the solution with attribute and it does not work correct.
> 

It does what you asked for originally, but you are shifting the
goalposts ...

> When i stop nfs_export_1 it stops data_1 data_1_active, then it starts
> data_2_failover - so far so good.
> 
> When i start nfs_export_1 it starts data_1, starts data_1_active and then
> stops data_2_failover as result of order data_1_active_after_data_1 and
> location data_2_failover_if_data_1_inactive.
> 
> But stopping data_2_failover unmounts the mount and end result is having no
> NFS export mounted:
> 

Nowhere before did you mention that you have two resources managing the
same mount point.

...
> Aug 17 15:24:52 intranet-test1 Filesystem(data_1)[16382]: INFO: Running
> start for nas-sync-test1:/home/pharmya/NAS on
> /data/synology/pharmya_office/NAS_Sync/NAS
> Aug 17 15:24:52 intranet-test1 Filesystem(data_1)[16382]: INFO: Filesystem
> /data/synology/pharmya_office/NAS_Sync/NAS is already mounted.
...
> Aug 17 15:24:52 intranet-test1 Filesystem(data_2_failover)[16456]: INFO:
> Trying to unmount /data/synology/pharmya_office/NAS_Sync/NAS
> Aug 17 15:24:52 intranet-test1 systemd[1]:
> data-synology-pharmya_office-NAS_Sync-NAS.mount: Succeeded.

This configuration is wrong - period. Filesystem agent monitor action
checks for mounted mountpoint, so pacemaker cannot determine which
resource is started. You may get away with it because by default
pacemaker does not run recurrent monitor for inactive resource, but any
probe will give wrong results.

It is almost always wrong to have multiple independent pacemaker
resources managing the same underlying physical resource.

It looks like you attempt to reimplement high available NFS server on
client side. If you insist on this, I see as the only solution separate
resource agent that monitors state of export/data resources and sets
attribute accordingly. But effectively you will be duplicating pacemaker
logic.