I have a classic Java webapp. It is composed of a database (PostgreSQL), a servlet container (Tomcat) and my code (deployed on Tomcat as a *.war file).
I want to package/deploy it using Docker (mostly for testing for now), but I'm unsure what would be the best way to "map" it.
My initial idea was to have an app-in-a-box - define a container that has Java, Postgres and Tomcat on it, exposing just the http port.
Further reading of the Docker docs shows that this, although possible (install and run supervisord as the single foreground process, have it start both Postgres and Tomcat) is probably not the intended usage. Going by the spirit of the tutorials I should probably create a container for Postgres, another for Tomcat, and a data-container to hold the application code (my *.war) and database files. This would mean 3+ containers (should the db files and *.war share the same data container?)
What's the common practice here?
Since I have no previous experience with Docker, what pitfalls can I expect from each approach?
Is there some other approach I'm missing?