[ClusterLabs] Start resource only if another resource is stopped

[Miro Igov]

Ok thank you for the advice. I learnt about the attribute resource, did not
knew about it before.
 
I left the idea of NFS failover and am switching an IP to the node which has
all required components.

Node List:
  * Online: [ intranet-test1 intranet-test2 nas-sync-test1 nas-sync-test2 ]

Full List of Resources:
  * admin-ip    (ocf::heartbeat:IPaddr2):        Started nas-sync-test2
  * stonith-sbd (stonith:external/sbd):  Started nas-sync-test1
  * data_2      (ocf::heartbeat:Filesystem):     Started intranet-test2
  * data_1      (ocf::heartbeat:Filesystem):     Started intranet-test1
  * nfs_export_1        (ocf::heartbeat:exportfs):       Started
nas-sync-test1
  * nfs_server_1        (systemd:nfs-server):    Started nas-sync-test1
  * nfs_export_2        (ocf::heartbeat:exportfs):       Started
nas-sync-test2
  * nfs_server_2        (systemd:nfs-server):    Started nas-sync-test2
  * nginx_1     (systemd:nginx):         Started intranet-test1
  * nginx_2     (systemd:nginx):         Started intranet-test2
  * mysql_1     (systemd:mysql):         Started intranet-test1
  * mysql_2     (systemd:mysql):         Started intranet-test2
  * php_1       (systemd:php5.6-fpm):    Started intranet-test1
  * php_2       (systemd:php5.6-fpm):    Started intranet-test2
  * intranet-ip (ocf::heartbeat:IPaddr2):        Started intranet-test2
  * nginx_1_active      (ocf::pacemaker:attribute):      Started
intranet-test1
  * nginx_2_active      (ocf::pacemaker:attribute):      Started
intranet-test2


intranet-ip is allocated at the node which has all of the data_x, php_x,
mysql_x and nginx_x resource. data_x requires having nfs_export_x and
nfs_server_x running on the sync nodes.
All working well thanks.

-----Original Message-----
From: Users <users-bounces at clusterlabs.org> On Behalf Of Andrei Borzenkov
Sent: Thursday, August 18, 2022 21:26
To: users at clusterlabs.org
Subject: Re: [ClusterLabs] Start resource only if another resource is
stopped

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.

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