Zabbix Agent 2 with PostgreSQL plugin creates multiple idle database sessions that do not close after query execution. The issue is observed in versions 6.0.33 and 6.4.0, while version 6.0.10 maintains only 1 connection as expected.

Component Versions:
 
 

Problem Symptoms:

Server 1 (zabbix-agent2 v6.4.20):

• 8 sessions from user zabbix

• All sessions in idle state

• Session lifetime: 2+ days

• Sessions distributed across databases: zabbix_proxy, postgres, zabbix_db1, zabbix_db2

Server 2 (zabbix-agent2 v6.0.33):

• 29 sessions from user zabbix

• All sessions in idle state

• Session lifetime: 5-6 days

• Sessions distributed across 12+ databases

• Duplicate sessions to the same databases (e.g., 2 sessions to zabbix_db4)

Server 3 (zabbix-agent2 v6.0.10):

• 2 sessions from user zabbix

• One active, one idle

• Normal behavior

Examples of Problematic Sessions:
 -- Server 2 (v6.0.33) - Duplicate sessions to zabbix_db4
datname     | pid | backend_start | query_start | state_change | state | query
zabbix_db4 | 2914 | 2025-11-04 17:42:42+05 | 2025-11-10 10:59:01.084798+05 | 2025-11-10 10:59:01.084806+05 | idle | SELECT 'Connected successfully' AS status
zabbix_db4 | 2953 | 2025-11-04 17:45:01+05 | 2025-11-10 10:59:01.084765+05 | 2025-11-10 10:59:01.084776+05 | idle | SELECT 2 + 2 AS result
Plugin Configuration (typical):
/etc/zabbix/zabbix_agent2.d/postgresql.conf
 Plugins.PostgreSQL.System.Path=/usr/sbin/zabbix-agent2-plugin/zabbix-agent2-plugin-postgresql Plugins.PostgreSQL.CustomQueriesPath=/etc/zabbix/scripts/psql
Reproduction Steps:

1. Install Zabbix Agent 2 v6.0.33+ with PostgreSQL plugin v6.0.13+

1. Configure monitoring for multiple databases (10+) using pgsql.custom.query key (10+ queries) with 1-minute collection interval

1. Observe idle session growth over time

1. Sessions remain open even after several days

Additional Observations:

• The KeepAlive parameter does not have the expected effect

• Connection pool management appears broken in affected versions

• Each custom query seems to create a persistent session instead of reusing connections