Building a Docker container can take quite a while. However, there are some easy parts to speed them up.
This is an article I had for quite a while as a draft. As part of my yearly cleanup, I've published it without finishing it. It might not be finished or have other problems.
Install Early, Copy Late ¶
Make sure you install dependencies early and copy code late during building the container. This helps to cache the dependencies.
You might also want to look at dependency pinning.
.dockerignore ¶
Make sure you don't re-build the container with stuff you don't need.
You can check the included files via
sudo docker build -t test .
sudo docker run --entrypoint /usr/bin/find -it test
sudo docker images | grep ^test
When I started looking at the size of my Flask image, it was 357MB.
Without copying any of the code, it was 349MB.