Supervisor: A Robust Process Control System for PHP Applications

Supervisor is a powerful tool for managing background processes, a necessity for PHP developers handling long-running tasks, queue workers, and other background jobs. This guide details Supervisor setup, PHP application integration, and comprehensive configuration for optimal performance.

Understanding Supervisor

Supervisor excels at managing background tasks by:

• Automatically restarting crashed processes.
• Centralized logging for easier monitoring.
• Command-line and web interface control.

It's particularly beneficial for PHP projects employing:

• Laravel queues for asynchronous processing.
• Persistent processes like WebSocket servers.
• Scheduled tasks akin to cron jobs.

Installing Supervisor

Ubuntu/Debian:

sudo apt update
sudo apt install supervisor

CentOS/RedHat:

sudo yum install epel-release
sudo yum install supervisor

Post-installation, activate and enable Supervisor:

sudo systemctl start supervisord
sudo systemctl enable supervisord

Supervisor Configuration

Supervisor utilizes configuration files (typically located in /etc/supervisor/conf.d/) to manage individual programs.

Basic Configuration Example:

Create /etc/supervisor/conf.d/my_php_worker.conf with this content:

[program:my_php_worker]
command=php /path/to/worker.php
autostart=true
autorestart=true
stderr_logfile=/var/log/my_php_worker.err.log
stdout_logfile=/var/log/my_php_worker.out.log

The --tries=3 option (within the command directive) limits restart attempts to three before failure.

Apply the configuration:

sudo supervisorctl reread
sudo supervisorctl update
sudo supervisorctl start my_php_worker:*

Detailed Configuration Options

Here's a detailed breakdown of Supervisor configuration options:

1. command: The command to execute. Example: command=php /path/to/worker.php

2. autostart: Automatically starts the program with Supervisor. Values: true (default), false. Example: autostart=true

3. autorestart: Automatic restart on failure. Values: true, false, unexpected. Example: autorestart=unexpected

4. startsecs: Minimum runtime (seconds) before a process is considered started. Default: 1. Example: startsecs=5

5. startretries: Maximum restart attempts before failure. Default: 3. Example: startretries=5

6. exitcodes: Acceptable exit codes preventing restarts. Default: 0,2. Example: exitcodes=0,1

7. stopwaitsecs: Time (seconds) to wait for graceful shutdown before forceful termination. Default: 10. Example: stopwaitsecs=20

8. redirect_stderr: Redirect standard error to standard output. Values: true, false (default). Example: redirect_stderr=true

9. stdout_logfile / stderr_logfile: Log file paths for standard output and error. Example: stdout_logfile=/var/log/my_program.out.log

10. stdout_logfile_maxbytes / stderr_logfile_maxbytes: Maximum log file size before rotation. Default: 50MB. Example: stdout_logfile_maxbytes=10MB

11. stdout_logfile_backups / stderr_logfile_backups: Number of rotated log files to retain. Default: 10. Example: stdout_logfile_backups=3

12. user: System user to run the program as. Example: user=www-data

13. environment: Environment variables. Example: environment=APP_ENV="production",DB_HOST="localhost"

14. priority: Start order (lower values start first). Default: 999. Example: priority=100

15. directory: Working directory. Example: directory=/path/to/your/app

16. stopasgroup: Send stop signal to the process and its children. Values: true, false (default). Example: stopasgroup=true

17. killasgroup: Forcefully kill the process and its children after stopwaitsecs. Values: true, false (default). Example: killasgroup=true

PHP-Specific Use Cases

1. Laravel Queues: Manage queue:work command for reliable job processing.

   sudo apt update
   sudo apt install supervisor

2. Scheduled Tasks: Replace cron for more robust scheduled script execution.

   sudo yum install epel-release
   sudo yum install supervisor

3. Long-Running Scripts: Manage persistent scripts like WebSocket servers.

   sudo systemctl start supervisord
   sudo systemctl enable supervisord

   Automating Supervisor Startup

   Ensure Supervisor starts on system boot:

   1. Enable Supervisor service: sudo systemctl enable supervisord

   2. Start the service (if needed): sudo systemctl start supervisord

   Best Practices

   • Use descriptive program names.
   • Configure log rotation using stdout_logfile_maxbytes and stdout_logfile_backups.
   • Utilize the environment directive to manage variables.

   Conclusion

   Supervisor is an essential tool for PHP developers managing background processes. This guide provides a comprehensive introduction to its installation, configuration, and practical applications, ensuring reliable and efficient task management for your PHP projects.

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