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Knowledge Base

Plesk never loads or fails with 502 Bad Gateway/504 Gateway errors

 
fastcgihttplinuxphpplesk server

Applicable to:

  • Plesk for Linux

Symptoms

  • Plesk never loads or fails with 502 Bad Gateway/504 Gateway errors.

  • One of the following error messages appears in
    /var/log/sw-cp-server/error_log
    :

    [error] 8074#0: *1046 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 203.0.113.2, server: , request: "GET /login_up.php3 HTTP/1.1", upstream: "fastcgi://unix:/var/run/sw-engine.sock", host: "example.com:8443"


    [error] 2550#0: *521 recv() failed (104: Connection reset by peer) while reading response header from upstream, client:203.0.113.2, server: , request: "GET /login_up.php3 HTTP/1.1", upstream: "fastcgi://unix:/var/run/sw-engine.sock:", host: "203.0.113.2:8443"

  • Restarting Plesk services has no effect:

    # systemctl restart sw-cp-server && systemctl restart sw-engine

Cause

Plesk panel services are stuck.

Resolution

  1. Connect to the Plesk server via SSH.

  2. Stop the sw-engine and sw-cp-server services:

    # systemctl stop sw-engine && systemctl stop sw-cp-server

  3. Find hanged sw-engine processes:

    # ps aux | grep sw-engine
    root 23173 0.0 0.3 383796 37504 ? SN 09:19 0:00 /usr/bin/sw-engine -c /usr/local/psa/admin/conf/php.ini /usr/local/psa/admin/plib/DailyMaintainance/script.php
    root 30148 0.0 0.3 398044 45916 ? SN 09:20 0:00 /usr/bin/sw-engine -c /usr/local/psa/admin/conf/php.ini /usr/local/psa/admin/plib/DailyMaintainance/task-script.php PleskUsage --period=daily
    root 30164 0.0 0.3 391748 38820 ? SN 09:20 0:04 /usr/bin/sw-engine -c /usr/local/psa/admin/conf/php.ini /usr/local/psa/bin/php_handler --list -json true

  4. Kill all listed above processes using their PID:

    # kill -9 23173 30148 30164

  5. Start Plesk services:

    # systemctl start sw-cp-server && systemctl start sw-engine

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