Adding a minute to some deployment process can be fairly significant. The docker push and pull is probably 70% of my deployment process and I already have ~100MB or less images.
I don't think the concern is 'how long does deployment take' but 'how fast can we iterate?'; Building and loading the images on a local dev machine to test a 2 second change would take much longer with larger images. Getting feedback of a PR merge from a CI build agent would take minutes longer.
> I don't think the concern is 'how long does deployment take' but 'how fast can we iterate?
And for iteration, the only thing that matters is the size of the top layers that are being iterated on. Not the overall image size itself.
You can put `RUN apt-get [kitchen sink]` at the beginning of the Dockerfile and it pretty much won't matter. When you change anything in the project repository, that bigass giant base layer doesn't get re-pulled because it doesn't change.
To validate that a layer, Docker daemon just compares the hashes. So, for unmodified layers, docker pull is constant time with image size. The Docker daemon only downloads from the registry starting with the bottom-most modified layer relative to its cache.
If anything, throwing the kitchen sink in the base layer is better for fast iteration. When you're being parsimonious about third-party libraries and packages, you'll frequently have to rebuild the base image. If you `RUN apt-get [everything]`, then you'll hardly ever never need to rebuild/re-push/re-pull that layer, because you'll always have whatever you need already available.
It depends on the size of project and what you want to optimize. The time spent on push and pull of docker images used to be a real deal breaker once upon a time when I tried to improve the deployment speed of a project by switching from heroku build to docker based solution
I don't think the concern is 'how long does deployment take' but 'how fast can we iterate?'; Building and loading the images on a local dev machine to test a 2 second change would take much longer with larger images. Getting feedback of a PR merge from a CI build agent would take minutes longer.
I don't think the importance has been oversold.