Best practices when copying source files with Docker

Question

Lastly, I have been trying to improve my Docker skills, but there is something I'm still stuck when I have to deal with it. Let's say I have an application divided into modules, each of them being its own Docker service.

All modules use the config stored under config/config.ini, but this config needs some preprocessing so what they use is the functions of config/config.py.

I have implemented that as:

• Each Dockerfile of each module COPY the contents of the config/ folder into their own ( COPY ./config . )
• Each module imports the config functions with: from config import ###

This method does work, but it breaks the IDE as the config folder is not on the pythonpath so I lost some important functionality, and what is worse I don't think this is the cleanest way of achieving what I want.

Furthermore, this also happens with source files. Normally in my python development, I would have just created a package called "APP" (see the folder structure below) and then I could have imported any source file in any folder of the package, but because each subfolder is a different Docker service I cannot make this project a python package. For example, the tests are also dockerized so each test also copies the needed source files from other folders:

the file unit_test_main_module.py needs to test all the source files in main_module so it copies the files with the Dockerfile.

APP
 ├── unit_tests
     ├── Dockerfile
     └── unit_test_main_module.py
 ├── integration_tests
     ├── Dockerfile
     └── first_integration_test.py
 ├── config
     ├── config.ini
     └── config.py
 └── main_module
     ├── source_file_one.py
     └── source_file_two.py

Any advice?

Answer 1

I would suggest having one Dockerfile per process . A Docker image is basically a self-contained way to run a process. So if you only ever run one process, you only need one Dockerfile.

You might want, perhaps, a second Dockerfile for a testing image. But you don't need one per package.

Assuming two, one for main application and one for tests, it would be in top directory.