Mastering Process Management with Supervisord

Mastering Process Management with Supervisord: A Comprehensive Guide

Introduction

In the dynamic world of system administration, ensuring that your services are running smoothly and reliably is paramount. supervisord is a powerful tool designed for this purpose, offering a robust solution for managing UNIX processes. This article will guide you through setting up and configuring supervisord to monitor and control your services, ensuring they run as intended without manual intervention.

What is Supervisord?

supervisord is an open-source process control system that allows you to monitor and control a group of processes on UNIX-like operating systems. It is written in Python and is easy to configure using simple INI-style configuration files.

Getting Started with Supervisord

Before diving into the configuration, you need to have supervisord installed on your system. You can install it using the package manager for your operating system, or by downloading the source code from the official website.

Basic Configuration

The configuration file for supervisord is typically located at /etc/supervisor/supervisord.conf. This file contains sections that define the behavior of supervisord itself, as well as the programs it will manage.

Here is a basic configuration example:

[supervisord]
nodaemon=true ; Run supervisord as a foreground process

[program:mysqld]
command=mysqld_safe ; Start the MySQL server

[program:php-server]
command=php -S 0.0.0.0:8000 -t /opt/app/ ; Start a PHP development server
autostart=true ; Automatically start the program when supervisord starts
autorestart=true ; Automatically restart the program if it exits
stderr_logfile=/var/log/php-server.err.log ; Log errors to this file
stdout_logfile=/var/log/php-server.out.log ; Log output to this file

[program:init_script]
command=/usr/local/bin/init_script.sh ; Run a custom initialization script
autostart=false ; Do not start the program automatically
startsecs=0 ; Number of seconds to wait after starting the process before sending a status check
autorestart=false ; Do not automatically restart the program if it exits
redirect_stderr=true ; Redirect standard error to standard output
stdout_logfile=/var/log/supervisor/init_script.log ; Log output to this file
stderr_logfile=/var/log/supervisor/init_script.err ; Log errors to this file

Key Configuration Options

• nodaemon: When set to true, supervisord will run as a foreground process instead of daemonizing.
• command: The command used to start the program.
• autostart: Whether the program should start automatically with supervisord.
• autorestart: Whether the program should be automatically restarted if it exits.
• stderr_logfile and stdout_logfile: The paths to the log files where the standard error and standard output of the program will be written.

Advanced Configuration

For more advanced use cases, supervisord offers additional configuration options such as environment variables, process priorities, and event listeners.

Monitoring and Control

Once your configuration is set up, you can use the supervisorctl command-line tool to control and monitor your processes. Some common commands include:

• supervisorctl status: Check the status of all programs.
• supervisorctl start program_name: Start a specific program.
• supervisorctl stop program_name: Stop a specific program.

Conclusion

supervisord is an invaluable tool for system administrators looking to streamline the management of their services. With its simple configuration and powerful features, it can help ensure that your services are always running at their best.

Further Reading

For more information on supervisord, including advanced usage and troubleshooting, you can refer to the official documentation and community forums.