I’ve mentioned before that I’ve rather taken a liking to Docker. However, there are a few things that I wish that were better.
Java doc did something extremely well. (Other than getting people to hate checkstyle) it made sure there there was a standard way to write documentation on your code base, and that it could be formatted in a proper, consistent way.
It would be great to see if there was a similar tool for Docker to produce consistent documentation on what the dockerfile produces. It would also be great to have registry support for this as well.
Some of the things that I would expect to see mentioned on there:
- Required environment variables for the application
- Documentation on maintenance to be done on the container (i.e. run particular methods via the exec command)
- Ports that should be shared
- What volumes are assumed to be there
- How the configuration should be set (is it a file, etc).
- How to connect the application with other services (databases, message queues, etc)
It would be great to generate best practice docker files based on if you’re working with a Tomcat application, or a standard Jar. This would get rid of the creation time needed to make a Dockerfile. Along with Dockerfile templates, it would be nice to see better Jenkins publishing support for Docker. However, that’s a subject for another day.
Multiple inheritance has a lot of issues that Java avoids, and C++ deals with. The issue with this is avoided in Python (with mixins), and Scala/Groovy with the addition of traits. Traits are aways to side load content into the docker file, post the base container, without having to use inheritance. That means that you could create a Docker container with utilities rather than baking them into the base image.
Applications typically have a limited set of configurations. They are either one time running applications or they’re web applications. There are sometimes deviations from this, but they’re not so common.
For the most part, one time running applications require a configuration set to go into the application and a location to write out the data. For web applications it mostly needs a port to be open, configuration to a data storage system (i.e. MySQL, MongoDB, etc), and configuration information.
The best way that I can forsee this being setup is to have a standard mount location for these folders outside of the container, and to have them set as required inputs for starting the container.
Another item on configuration. I would love to see the configuration copied from the container to its outside storage for the starter configuration. This would mean that the Docker Registry complex configuration would have a new mounted volume outside of the container there with a configuration ready to have a change made to it.