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Knowledge Base

Plesk interface is down or slow: server reached max_children setting

 
dbinterfacemysqlphpplesk for linux

Symptoms

  • Plesk is inaccessible with one of the following errors:

    DB query failed: SQLSTATE[HY000] [2002] Resource temporarily unavailable
    Type PleskExceptionDatabase
    Message DB query failed: SQLSTATE[HY000] [2002] Resource temporarily unavailable
    File Mysql.php
    Line 60

    Server Error
    502 Bad Gateway
    Web server received an invalid response while acting as a gateway or proxy server.

  • These errors are logged to /var/log/sw-cp-server/sw-engine.log:

    [pool plesk] server reached max_children setting (26), consider raising it

Cause

The Plesk panel reached its pm.max_children limit.

Resolution

Increase the limit.

  1. Log in via SSH

  2. Increase the pm.max_children value in /etc/sw-engine/pool.d/plesk.conf:

    # sed -i.bkp 's/max_children.*/max_children = 50/' /etc/sw-engine/pool.d/plesk.conf

    Note: The command above increases the limit to 50. Increase it further if the error continues.

  3. Restart sw-engine in order to apply the changes:

    # service sw-engine restart

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