Within the Docker community there tends to be two modes of thought with regard to running processes: run multiple supervised processes in a container or only run a single process per container. The former makes it easier to encapsulate applications that may need more than one service (think NGiNX + uWSGI + Memcached + Redis) while the latter makes more sense because Docker only supports running a single command. This article will be about the former, using Supervisor to supervise multiple processes and log their output.

One major issue with running multiple processes in a Docker container is getting access to log output. There are lots of logging services out there designed to ease the burden and aggregate multiple Docker container logs into a single location for storage and analysis, but in this case we’re only interested in a single container. By default, Supervisor logs to a specific file for each of its child processes. While this is great for organization, it’s a hassle when running inside a Docker container. Since we can see the standard output and error from the Docker container itself and docker logs gives us the same information if the container is running as a daemon, ideally we should be able to see our basic logs the same way.

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