read-write acces necessary?

[marcelmikusik]

Hello have you use "postgres" USER for monitoring?
What about to use read only access role to monitor? For example zabbix user.

[rsn86]

Write permission isn't necessary.

Starting of PostgreSQL 10 you can use a regular user with the default role pg_monitor.
CREATE ROLE zabbix WITH LOGIN NOSUPERUSER; GRANT ROLE pg_monitor TO zabbix;

Before that, you have to ensure that user has GRANT SELECT on ALL monitored objects and to monitor streaming replication you can create a helper function with security definer.
Take a look at #6 (comment)
Run that as user postgres at PGDATABASE database (postgres by default).

Regards,
Rodrigo