Optimised Dockerfile for fast, cached builds

[angadn]

No description provided.

[twerkmeister]

@angadn yet another contribution, thanks a lot! Good idea with the caching. Can you give me a short explanation why you remove -e . from the requirements.txt just to add it later again?

[angadn]

@twerkmeister the idea is to first install all dependencies without copying in our own code-base inside the container, which we'd have to do if we were installing our modules alongside; since Docker would then watch our files for change, and install all dependencies afresh. In this case, you'll notice that if you try to move the COPY instruction to after the requirements-setup, it will throw an error saying it couldn't find setup.py in the current directory (copy that file in isolation, and errors start cascading all the way to inside our folder-structure).

On line 26, I concatenate the -e . ahead of the requirements, and ask for install again - this time, all the cached dependencies are already found, and just our modules are installed!

[twerkmeister]

Thanks for the explanation! What happens now if someone executes setup.py outside of the docker build file? Then the -e is missing unless they add it manually. Wouldn't it be better if: 1) we keep the -e in requirements.txt, 2) copy requirements.txt it into the container, 3) create a requirements-nonlocal.txt by cutting of the -e with something like cat requirements.txt | grep -v "^-e .$" > requirements-nonlocal.txt and 4) execute pip install -r requirements-nonlocal.txt. This way the non-docker build processes wouldn't be affected at all

[angadn]

Crap - to be honest, this is the first time I'm working on a Python codebase in months; makes sense, I shall make this change and update the PR as soon as I'm back at work!

[tmbo]

@angadn please let us know when you have an updated version, this is quite a neat contribution 👍

[angadn]

Pushed update as per suggestions - testing out the build process locally now and will push fixes if necessitated

[angadn]

Not sure why 1 check is failing - can you please point me in the right direction

[tmbo]

@angadn that issue is not related to your code, merging in the latest master should resolve it.

[angadn]

Whoops - done. Hope this helps

[tmbo]

@twerkmeister please merge if you feel everything is good to go.

[twerkmeister]

Good stuff @angadn, thanks for the changes!