Where to keep Dockerfile's in a project?

Question

I am gaining knowledge about Docker and I have the following questions

• Where are Dockerfile's kept in a project?
  • Are they kept together with the source?
  • Are they kept outside of the source? Do you have an own Git repository just for the Dockerfile?

If the CI server should create a new image for each build and run that on the test server, do you keep the previous image? I mean, do you tag the previous image or do you remove the previous image before creating the new one?

I am a Java EE developer so I use Maven, Jenkins etc if that matter.

Answer 1

The only restriction on where a Dockerfile is kept is that any files you ADD to your image must be beneath the Dockerfile in the file system. I normally see them at the top level of projects, though I have a repo that combines a bunch of small images where I have something like

top/   project1/     Dockerfile     project1_files   project2/     Dockerfile     project2_files   

The Jenkins docker plugin can point to an arbitrary directory with a Dockerfile, so that's easy. As for CI, the most common strategy I've seen is to tag each image built with CI as 'latest'. This is the default if you don't add a tag to a build. Then releases get their own tags. Thus, if you just run an image with no arguments you get the last image built by CI, but if you want a particular release it's easy to say so.