If you're seeing 503 Service Unavailable errors in your website, this means PHP processes are crashing while executing a script. As a result, Apache is not getting a valid response from PHP and considers the PHP-FPM service to be unavailable. The possible cases for this error are as follows;
- The most common cause of this problem is buggy PHP code, such as buggy WordPress plugins or slow scripts. The best solution is to check your app's PHP error log and PHP slow log. You have to make sure your script is compatible with the latest PHP version as well. Please check with your developer if you are unable to get more information from you logs. If you are using WordPress, please disable all your plugins and try to isolate the buggy plugin.
- If the error is intermittent/not continuous, it's possible that the PHP process crashes because of a blocked resource. Typically this happens if any required resource path is blocked by our web application firewall (WAF). Please open a ticket to the technical support department if you need logs to get this situation resolved.
