Identifying and resolving common problems in a PHP-FPM environment involves troubleshooting issues related to performance, configuration, and functionality. Here are some common problems you may encounter with PHP-FPM and steps to resolve them:
PHP-FPM not starting or crashing
- Check PHP-FPM logs for error messages:
tail -f /var/log/php8.x-fpm.log
- Verify PHP-FPM configuration for syntax errors:
php-fpm8.x -t
- Check system resource utilization (CPU, memory) to ensure it's not overloaded.
504 gateway timeout error
Increase the request_terminate_timeout setting in PHP-FPM pool configuration to allow longer script execution.
High Memory Usage by PHP-FPM
Adjust the pm.max_children and pm.max_requests settings in the pool configuration to limit the number of PHP-FPM processes and control memory usage.
PHP errors displayed in the browser
Disable error display in the PHP configuration by setting display_errors to Off in php.ini.
Website serving outdated content:
Clear the PHP-FPM opcode cache (e.g., OPcache) or restart PHP-FPM to ensure the latest changes take effect.
Slow PHP-FPM performance:
- Check for slow database queries or external API calls.
- Enable PHP-FPM slow log to identify slow scripts:
request_slowlog_timeout = 5s
slowlog = /var/log/php8.x-fpm-slow.log
Unable to connect to PHP-FPM unix socket:
Verify the correct path to the PHP-FPM Unix socket in your web server configuration (e.g., Nginx or Apache).
502 Bad gateway error:
- Check PHP-FPM logs for error messages.
- Ensure that the web server (Nginx, Apache) can communicate with PHP-FPM.
- Verify PHP-FPM pool configuration for errors.
File permission issues:
- Ensure that PHP-FPM has the necessary permissions to access the files and directories.
- Adjust file permissions and ownership appropriately.
PHP extensions or libraries missing:
- Check PHP-FPM logs for any errors related to missing extensions.
- Install the required PHP extensions using the package manager.
Session issues:
- Ensure that the session save path is writable by PHP-FPM.
- Check for issues related to session configuration in php.ini.
Database connection issues:
- Verify database credentials in the application's configuration.
- Check for database server availability and connectivity.
Unable to start PHP-FPM after configuration changes:
- Run a syntax check on the PHP-FPM configuration:
php-fpm8.x -t
- Check for errors in the configuration file and correct them.
Inconsistent PHP-FPM and web server configurations:
- Ensure that PHP-FPM and the web server (Nginx, Apache) configurations are in sync.
- Check for discrepancies in the configuration files.
Important considerations:
Backup configurations:
Before making significant changes, back up your PHP-FPM and web server configurations to avoid data loss.
Logs and monitoring:
Regularly review logs and monitor system metrics to identify potential issues early on.
Security considerations:
Be mindful of security implications when making changes to configurations. Avoid exposing sensitive information in error messages.
Documentation:
Refer to official PHP, PHP-FPM, and web server documentation for accurate and up-to-date information.
By systematically troubleshooting and addressing these common problems, you can ensure the stability, performance, and reliability of your PHP-FPM environment.