During performance testing of Zabbix Agent 2 (Go) on Linux Mint 21.1, a severe performance degradation was identified in the net.udp.listen key. While Agent 2 is architecturally concurrent, the current implementation introduces a consistent 1-second overhead per request.

Steps to reproduce:

• Use socat to open a large range of UDP ports (e.g., 10000-12000):

for port in {10000..12000}; do
  socat UDP-LISTEN:$port,fork /dev/null &
done 

• Monitor execution time using:

time sbin/zabbix_agent2 -t net.udp.listen[11000]

• Compare with zabbix_agentd:

time sbin/zabbix_agentd -t net.udp.listen[11000]

Result:
Please see actual performance test results: ZBX-27377 - actual results.txt
Expected:

• net.udp.listen must be as fast as Agent 1. A 1-second delay is too slow and may cause data queues.
• Return type: Must be the same as in Agent 1:  [u|1].