Site does not work on PHP-FPM on Plesk: 503 service unavailable

Daniel Yordanov

Updated January 20, 2025 19:58

Plesk for Linux kb: technical ABT: Group A

Applicable to:

Plesk for Linux

Symptoms

Sites that use the same PHP-FPM version (for example, 7.2 are not working):

CONFIG_TEXT: 503 service unavailable
The following error appears in the domain's error log /var/www/vhosts/system/example.com/logs/error_log:

CONFIG_TEXT: [proxy_fcgi:error] [pid 15605:tid 140353550149376] [client 203.0.113.2:45388] AH01079: failed to make connection to backend: httpd-UDS
[proxy:error] [pid 15605:tid 140353373902592] (2)No such file or directory: AH02454: FCGI: attempt to connect to Unix domain socket /var/www/vhosts/system/example.com/php-fpm.sock (*) failed
Socket /var/www/vhosts/system/example.com/php-fpm.sock does not exist and switching PHP handler to another one at Plesk > Domains > example.com > PHP Settings recreates it, but switching PHP handler back removes it again
Running the plesk repair web -n command provides output that is similar to the following:

CONFIG_TEXT: Checking for obsolete PHP-FPM configuration files
Domain example.com ............................................. [ERROR]
- Domain example.com with PHP handler plesk-php82-fpm has
obsolete PHP-FPM configuration file
/opt/plesk/php/8.1/etc/php-fpm.d/example.com

Cause

The php-fpm.sock files for several domains are missing, because the PHP-related configuration files for the affected domains and PHP versions have either become corrupted or have gone missing entirely.

Resolution

Log into the server via SSH
Restart all PHP-FPM services that are assigned to domains by executing the following command:

# systemctl restart plesk-php*
Recreate the missing or corrupted configuration files and PHP sockets for all domains by executing the following command:

# plesk repair web -y

If the 503 issues persist for some sites that use a specific PHP version, files that are corrupted remain, due to which you should do the following in order to recreate all of them from scratch:

1. Create a list of sites that use the specific PHP version by using the following example:

# plesk db -sNe "select name from hosting h,domains dom where dom.id = h.dom_id and php = 'true' AND php_handler_id LIKE 'plesk-php82-fpm'" domains.txt

2. Make sure a similar PHP version to the one the domains are using in the example is enabled ( plesk-php82-fastcgi for the purposes of this example) on the server

3. Switch all domains from the domains.txt file to that similar PHP version by executing the following command:

# cat domains.txt | while read i; do echo "[+] Updating domain: $i"; plesk bin domain -u $i -php_handler_id plesk-php83-fastcgi; done

4. Run the following command:

# plesk repair web -php-fpm-configuration

5. Switch all domains back to the previously used PHP version by using the following command:

# cat domains.txt | while read i; do echo "[+] Updating domain: $i"; plesk bin domain -u $i -php_handler_id plesk-php83-fpm; done