HTTP Agent causes hanging CLOSE_WAIT connections in Docker container

[Shadown]

Hello everyone,

I’m running into an issue with my Zabbix setup while monitoring a Proxmox environment using the official “Proxmox VE by HTTP” template.

• Zabbix Server is running inside a Docker container.
• Proxmox hosts are monitored via the official HTTP template.
• The connection to the Proxmox API is made over port 8006.
• The Proxmox host is reachable via IP, for example 192.168.210.2:8006.
• Server version: 7.4.12

After a short runtime of about 15 to 30 minutes, the TCP connections to the Proxmox API get stuck in the CLOSE_WAIT state.

tcp        1      0 34a1a00fcd10:52880      192.168.210.2:8006      CLOSE_WAIT  
tcp        1      0 34a1a00fcd10:35162      192.168.210.2:8006      CLOSE_WAIT  
tcp        1      0 34a1a00fcd10:47348      192.168.210.2:8006      CLOSE_WAIT  
tcp        1      0 34a1a00fcd10:57528      192.168.210.2:8006      CLOSE_WAIT  
tcp        1      0 34a1a00fcd10:56086      192.168.210.2:8006      CLOSE_WAIT  
.
.
.

This is my Docker Compose configuration for the Zabbix server:

zabbix-server:
    image: zabbix/zabbix-server-pgsql:alpine-7.4-latest
    #ulimits:
    # nproc: 65535
    # nofile:
    #  soft: 20000
    #  hard: 40000
    container_name: zabbix-server
    restart: unless-stopped
    depends_on:
      - postgresql-server
    environment:
      DB_SERVER_HOST: postgresql-server
      POSTGRES_USER: ${POSTGRES_USER}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
      POSTGRES_DB: ${POSTGRES_DB}
      ZBX_NODEADDRESS: zabbix-server
      ZBX_NODEADDRESSPORT: 10051
      ZBX_STARTREPORTWRITERS: 3
      ZBX_WEBSERVICEURL: "http://zabbix-web-service:10053/report"
      ZBX_STARTHTTPPOLLERS: 1
      ZBX_DEBUGLEVEL: 3
      CURL_IPRESOLVE: 4
    ports:
      - "10051:10051"
    volumes:
      - zabbix-server-data:/var/lib/zabbix
      - zabbix-snmptraps-data:/var/lib/zabbix/snmptraps
      - zabbix-export-data:/var/lib/zabbix/export​

When I enable the ulimit parameters, the issue still persists, but it takes longer to occur.