Supervisor Process Monitoring and Management Guide

Supervisor is a client/server process monitoring and management tool for Unix-like operating systems. It monitors target processes, automatically restarts them on unexpected termination, and supports grouping multiple processes for unified control.

1. Overview

Supervisor solves stability issues for persistent background processes such as API services or consumers.

2. Problem Scenario

Typical deployment uses nohup cmd & , which cannot guarantee stable long‑running processes; Supervisor addresses this limitation.

3. Supervisor Introduction

Supervisor is a client/server system that allows its users to control a number of processes on UNIX‑like operating systems.

Key features include state monitoring, automatic restart, and group management.

4. Deployment Process

4.1 Install Supervisor

Install via pip:

<code>pip install supervisor</code>

Note: Supervisor does not support Windows.

4.2 Create Service Configuration

Generate a base config file:

<code>echo_supervisord_conf > /etc/supervisord.conf</code>

Key sections such as [unix_http_server] , [supervisord] , and [supervisorctl] define socket paths, logging, and PID files.

4.3 Create Application Config

For a test project with test.py , create supervisor-test.ini :

<code>[program:test]
command=python -u ./test.py
directory=/root/test/
redirect_stderr=true
stdout_logfile=/root/test/test.log</code>

Link it into the include directory:

<code>ln ./supervisor-test.ini /etc/supervisord.d/supervisor-test.ini</code>

4.4 Start supervisord

Run the daemon:

<code>supervisord</code>

Specify a config file with -c if needed.

4.5 Use supervisorctl

Interact with the daemon:

<code>supervisorctl</code>

Check status, start, stop, restart processes, and view logs with tail -f .

5. Advanced Features

5.1 Process Group Management

Define groups using [group:mygroup] and list member programs.

<code>[group:test]
programs=test-task_service, test-collector

[program:test-task_service]
command=python -u ./task_service.py

[program:test-collector]
command=python -u ./collector.py</code>

5.2 Program Configuration Parameters

command : command to run.

directory : working directory.

numprocs : number of process instances.

autostart : start on supervisord launch.

stdout_logfile , stdout_logfile_maxbytes , stdout_logfile_backups : log handling.

redirect_stderr : merge stderr into stdout.

5.3 supervisorctl Commands

Use help to list commands; common ones include status , start , stop , restart , signal , update , reload , and shutdown .

5.4 Signal Handling in Applications

Python example registers a handler for SIGTERM to perform cleanup before exit.

<code>import time, signal
RUN = True

def exit_handler(signum, frame):
    print(f'processing signal({signal.Signals(signum).name})')
    print('update task status')
    print('clear cache data')
    global RUN
    RUN = False

signal.signal(signal.SIGTERM, exit_handler)
while RUN:
    print(time.strftime('%Y-%m-%d %H:%M:%S'))
    time.sleep(1)
print('exited')</code>

5.5 Web UI

Enable [inet_http_server] in /etc/supervisord.conf to access a web interface on port 9001.

6. Simple Analysis of Auto‑Restart Mechanism

The autorestart option controls whether supervisord restarts a process after exit. Values:

autorestart=unexpected (default): restart on non‑expected exit codes.

autorestart=true : always restart, even on normal exit.

autorestart=false : never restart.

Combined with exitcodes , startsecs , and startretries , you can fine‑tune restart behavior.

7. Conclusion

Supervisor provides a robust solution for managing persistent processes, supporting custom configurations, process groups, automatic restarts, signal handling, and optional web UI, making it valuable for reliable service deployment and operations.