Supervisor-Introduction

In this repo I'm going to talk about how to run/manage a python script using superviosr.

Overview of supervisor

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

Componets of supervvisor...* (i) Supervisord: Server piece of supervisor which responsible for...
(a) starting child program at its own invocation
(b) responding to commands from clients
(c) restarting crashed or exited subprocesses
(d) logging stdout and stderr output of its subprocess
(e) generating and handling events corresponding to points in subprocess lifetimes.
(ii) Supervisorctl: command-line client piece of the supervisor which provides a shell-like interface to the features provided by supervisord.

Installation of supervisor

open terminal and then run the following command
sudo apt-get install supervisor

Run supervisor

After installing the supervisor, to run it (run the following command in terminal)
sudo supervisord

Before running the above command please make sure you using system python, not anaconda python (how to check which python you are using--- run which python or which python3 in terminal and see the output.)

Some other command to restart, stop and check status of supervisor

#Checking the status of supervisor
  sudo service supervisor status
#Staring supervisor
  sudo service supervisor start
#Stopping supervisor
  sudo service supervisor stop
#Restarting supervisor
  sudo service supervisor restart

Creating a simple python program

You may create this script earlier also. there is no hard-and-fast rule to create the python script after running the supervisor I have created a 'demo.py' file i.e. basically print a message after 1 second.

Configuration

To get supervisor to execute a certain program or script, we can configure it in the /etc/supervisor/conf.d/ directory. As a recommendation, it would be best to keep a single conf file per process.

So to create a configuration file I have sued 'vim'. Just type the following command in terminal

sudo vim /etc/supervisor/conf.d/demo.conf

(change 'demo' with your conf file name. I have given my conf file name 'demo')

after running the above command press i (that will take in insert mode), now you can write your configuration

  [program:demo]
  command=python -u demo.py
  directory=/home/my_username
  #where output log will store
  stdout_logfile=/var/log/demo.out.log
  #where error log will store
  stderr_logfile=/var/log/demo.err.log
  redirect_stderr=true
  #if processes should start when supervisor starts
  autostart=true
  #if proceses should restart when they stop while running
  autorestart=true

Now press esc key and then wrire :w press ENTER and then write :q press ENTER.

######Now run the following command sudo systemctl restart supervisor.service

Next step

To get into supervisorctl, use the following command

sudo supervisorctl

if you are getting unix:///tmp/supervisor.sock no such file error then try to run supervisorctl with -c parameter-

sudo supervisorctl -c /etc/supervisor/supervisord.conf

Now a supervisorctl prompt will open, try to run the following

supervisor > reread #Reloads conf files
supervisor > add test_process #Adds a newly created conf file and starts the process
supervisor > status # Checks all status of programs managed by supervisor

Additional

If you want to see your supervisord.conf file then you can see it here /etc/supervisor/supervisord.conf

References

https://medium.com/@jayden.chua/use-supervisor-to-run-your-python-tests-13e91171d6d3

https://medium.com/@joor.loohuis/using-supervisor-for-process-management-66a5cc3d3dfa

http://supervisord.org/introduction.html

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