Supervisor in a Docker (CentOS and Alpine version available)

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This is a Supervisor Docker polinux/supervisor image, perfect in case when you need to launch more then one process inside a container.

What's included

- bootstrap.sh script

The container has an ENTRYPOINT set to /config/bootstrap.sh. It iterates through all /config/init/*.sh scripts and runs them, then launches supervisord. See bootstrap.sh for details.

By default, the CMD option in Dockerfile is empty, but the bootstrap.sh script is configured to run everything which is passed into it. Therefore you can launch it in several ways:

• detached mode, no argument(s) passed: supervisord starts in foreground mode and stays until container is stopped.
• detached mode, some argument(s) passed: arguments are executed; supervisord starts in foreground mode and stays until container is stopped.
• interactive mode with TTY (-it), no argument(s) passed: supervisord starts in background mode; interactive bash waits for user input. Exiting from bash (CMD+D) exists the container.
• interactive mode with TTY (-it), some argument(s) passed: supervisord starts in background mode, passed command is executed; container exits.

- supervisord

Supervisord is installed and loads services to run from /etc/supervisor.d/ directory. Add your own files there to launch your services. For example in your Dockerfile you could put: ADD my-supervisord-service.conf /etc/supervisord.d/my-supervisord-service.conf

Learn more about about supervisord inside containers on official Docker documentation.

- init scripts

You can add your .sh scripts to /config/init directory to have them executed when container starts. The bootstrap script is configured to run them just before supervisord starts.

- error logging

Logfile for supervisord is switched off to avoid logging inside container. Instead, all logs are easily available via docker logs [container name].

This is probably the best approach if you would like to source your logs from outside the container via docker logs (also via CoreOS `journald') and you do not want to worry about logging and log management inside your container and/or data volume.

- /data volume

The /data directory is meant to be used to simply and easily deploy web applications using a volume binding on /data, presumably using data only containers pattern.

Recommended structure:

/data/run/ # pid, sockets
/data/conf/ # extra configs for your services
/data/logs/ # logs
/data/www/ # your web application data

Usage

As explained above, this container is configured to run your service(s) both in interactive and non-interactive modes.

docker run -it polinux/supervisor: runs supervisord, then interactive bash shell and waits for user's input. Exiting from the shell kills the container.

docker run -it polinux/supervisor ps aux: runs supervisord, then ps aux command inside container and exists.

docker run -it polinux/supervisor top: runs supervisord, then top tool. Exiting from top exits the container.

docker run -d polinux/supervisor: detached, runs supervisord in foreground mode and its configured services

docker run -d polinux/supervisor touch 'test-file': detached, runs touch 'test-file' command, then supervisord in foreground mode and its configured services

Build

docker build --tag=polinux/supervisor .

Author

• Przemyslaw Ozgo (linux@ozgo.info)