Pgsql resource agent of pacemaker

Hello,

Need advise on below situation:

Postgres 9.6
Pacemaker 1.1.19
Corosync 2.4.3

We are testing HA setup on a two node cluster using pacemaker, corosync
stack. The replication is streaming replication in async mode.
Whenever there is a failover to standby, pgsql created a PGSQL.lock file in
/var/lib/pgsql/tmp/ folder. We noticed that this file is created at random
on any one of the nodes.

Want to know:
- Is there any logic behind which node it creates the lock file?

- When a node in kept in HS:alone state ?

- How can we check if failed node is at a log location behind current
primary? So that we can force RA to start by deleting lock file?

Please help to understand

Thanks.