Docker development workflow

Question

What's the proper development workflow for code that runs in a Docker container?

Solomon Hykes said that the "official" workflow involves building and running a new Docker image for each Git commit. That makes sense, but what if I want to test a change before committing it to the Git repo?

I can think of two ways to do it:

1. Run the code on a local development server (e.g., the Django development server). Edit a file; test on the dev server; make a Git commit; rebuild the Docker image with the new code; test again on the local Docker container.

2. Don't run a local dev server. Instead, build and run a new Docker image each time I edit a file, and then test the change on local Docker container.

Both approaches are pretty inefficient. Is there a better way?

Answer 1

A more efficient way is to run a new container from the latest image that was built (which then has the latest code).

You could start that container starting a bash shell so that you will be able to edit files from inside the container:

docker run -it <some image> bash -l

You would then run the application in that container to test the new code.

Another way to alter files in that container is to start it with a volume. The idea is to alter files in a directory on the docker host instead of messing with files from the command line from the container itself:

docker run -it -v /home/joe/tmp:/data <some image>

Any file that you will put in /home/joe/tmp on your docker host will be available under /data/ in the container. Change /data to whatever path is suitable for your case and hack away.