nginx proxy_error ai_generated true

connect() failed (111: Connection refused) while connecting to upstream

ID: nginx/upstream-connection-refused

Also available as: JSON · Markdown
88%Fix Rate
90%Confidence
3Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1 active — — —

Root Cause

nginx cannot reach the backend. Backend not running, wrong port, or listening on different interface.

generic

Workarounds

  1. 95% success Verify the backend is running and listening on the expected port 
    curl -v http://127.0.0.1:8000  # test backend directly; ss -tlnp | grep 8000

    Sources: https://nginx.org/en/docs/

  2. 90% success Check backend is listening on correct interface (0.0.0.0 vs 127.0.0.1) 
    If backend listens on 127.0.0.1 but nginx uses proxy_pass to container IP, connection refused
  3. 82% success Check firewall rules and SELinux if enabled 
    sudo setsebool -P httpd_can_network_connect 1  # SELinux blocks nginx upstream by default

Dead Ends

Common approaches that don't work:

  1. Change proxy_pass to use hostname instead of IP 55% fail

    DNS resolution adds latency and can fail; use IP for local backends

  2. Restart nginx assuming the issue is with nginx 80% fail

    nginx is working correctly by reporting the error; the backend is the problem