Website fails to load periodically with a 503 error. Failed to read FastCGI header

Sergey Senko

Updated June 14, 2025 12:12

Plesk for Linux kb: technical plesk for linux php

Symptoms

Website fails to load periodically with a 503 error.
The following messages appear in domain's log:

CONFIG_TEXT: [proxy_fcgi:error] [pid 2915996:tid 140490896815872] [client 203.0.113.2] AH01067: Failed to read FastCGI header
[proxy_fcgi:error] [pid 2915996:tid 140490896815872] (104)Connection reset by peer: [client 203.0.113.2] AH01075: Error dispatching request to :

Some Apache/PHP-FPM processes got stuck.

Go to Domains > example.com > PHP Settings:
Change the PHP version to another and then back to the original.