Symptoms

Websites or site's preview that use php-fpm show following errors: 502 Bad Gateway or 504 Gateway Timeout

In /var/log/php-fpm/error.log the following record can be found:

NOTICE: Reloading in progress ...

Or any similar error.

Cause

php-fpm service is hung or down.

Resolution

Restart the php-fpm service:

# service php-fpm restart

Note: service may be plesk-php56-fpm, plesk-php55-fpm and etc. It depends on handler that is being used for domain.