A site that uses a specific PHP-FPM handler on a Plesk server does not open: 503 Service Unavailable

Daniel Yordanov

Updated December 03, 2024 15:17

Plesk for Linux kb: technical

Applicable to:

Plesk for Linux

Symptoms

The domain example.com that displays one of the following errors when opened in a browser:

PLESK_INFO: 503 Service Unavailable

PLESK_INFO: 502 Bad Gateway
Nginx
Errors that are similar to the following appear in the domain's Apache error log /var/www/vhosts/system/example.com/logs/error_log:

CONFIG_TEXT: [proxy:error] [pid 15065:tid 139826443527936] (111)Connection refused: AH02454: FCGI: attempt to connect to Unix domain socket /data/vhosts/system/example.com/php-fpm.sock (*) failed
[proxy_fcgi:error] [pid 15065:tid 139826443527936] [client 203.0.113.2:50232] AH01079: failed to make connection to backend: httpd-UDS
Errors that are similar to the following appear in the domain's nginx error log:

CONFIG_TEXT: 2024/02/12 10:31:43 [error] 26259#0: *595 connect() to unix:/var/www/vhosts/system/example.com/php-fpm.sock failed (111: Connection refused) while connecting to upstream, client: 2001:db8:f61:a1ff:0:0:0:80, server: example.com, request: "GET / HTTP/2.0", upstream: "fastcgi://unix:/var/www/vhosts/system/example.com/php-fpm.sock:", host: "example.com"

Cause

The PHP configuration file that should exist for the PHP version that the affected domain is set to use is missing from the /opt/plesk/php/X.X/etc/php-fpm.d/ directory.

Note: This can often occur if a PHP handler was removed entirely from Plesk, as explained in this article.

Resolution

Regenerate the PHP configuration files for the domains on your server by executing the following steps:

For a single domain

Log into Plesk
Go to Domains > example.com > Dashboard > PHP, change the used PHP handler to any different one and press Apply
Change the PHP handler version back to the original one and press Apply

For all domains

Log into the server via SSH

Note: If direct SSH access to the server is not possible, contact server administrator for further assistance.
Execute the following command to update settings on all domains:

# /usr/local/psa/bin/php_settings -u
Execute the command to get a list of all installed PHP handlers:

# plesk bin php_handler --list | grep -E plesk.*fpm | awk -F" " '{ print $1 }'

plesk-php74-fpm
plesk-php81-fpm
plesk-php82-fpm
plesk-php83-fpm
Restart the PHP handler service for all of the used PHP handlers, for example:

# systemctl restart plesk-php74-fpm

# systemctl restart plesk-php81-fpm

# systemctl restart plesk-php82-fpm

# systemctl restart plesk-php83-fpm