To monitor PostreSQL server you need :

1. Install psycopg2 module.
2. Create PostreSQL user with privileges pg_monitor.
3. Configure Agent with User/Pass/Host, for connecting to Postgres server.

Install PostreSQL Python client

For Debian or Ubuntu

apt-get install python3-psycopg2

For RHEL / Rocky / AlmaLinux

sudo dnf install python3-psycopg2

PostreSQL drivers can be installed via PIP as well.

pip3  install psycopg2

Create PostreSQL User

Login to your PostreSQL server as superuser

sudo -u postgres psql

and execute following statement :

CREATE
USER monitor WITH PASSWORD 'your_secure_password';
GRANT pg_monitor TO monitor;

Configure Agent

Copy or symlink checks_available/check_postgres.py to checks_enabled

cd ${AGENT_HOME/checks_enabled}
ln -s ../checks_available/check_postgres.py ./ 

Edit confconf/sql_cache.ini and put right parameters at PostreSQL section:

[Postgres]
host : 127.0.0.1
user : monitor
pass : your_secure_password

Provides

Name	Description	Type	Unit
psql_xact_commit	Committed PostgreSQL transactions	rate	TPS
psql_xact_rollback	Rolled back PostgreSQL transactions	rate	TPS
psql_rollback_ratio	Ratio of rolled back transactions to total transactions	current	Ratio
psql_numbackends	Number of active client connections to the database	current	None
psql_blks_read	Disk blocks read from storage	rate	Blocks
psql_blks_hit	Shared buffer cache hits	rate	Blocks
psql_cache_hits_ratio	PostgreSQL shared buffer cache hit ratio	current	Ratio
psql_tup_returned	Rows returned by sequential and index scans	rate	Rows/s
psql_tup_fetched	Rows fetched by index scans	rate	Rows/s
psql_tup_inserted	Rows inserted	rate	Rows/s
psql_tup_updated	Rows updated	rate	Rows/s
psql_tup_deleted	Rows deleted	rate	Rows/s
psql_write_amplification	Total modified rows (inserted + updated + deleted)	rate	Rows/s
psql_temp_files	Temporary files created by queries	rate	Files/s
psql_temp_bytes	Temporary data written to disk	rate	Bytes
psql_deadlocks	Deadlocks detected	rate	Events/s
psql_conflicts	Query conflicts on standby servers	rate	Events/s
psql_checksum_failures	Data checksum failures detected	rate	Events/s
psql_stats_reset	Timestamp when PostgreSQL statistics were last reset	current	Timestamp