Create docker

[Corentin Dupont]

Hi,

I'm trying to create a docker container for my application (to deploy it on Amazon ECS).

I'm using https://github.com/freebroccolo/docker-haskell

However, the images generated are huge: from 4 Go to 7Go.

https://github.com/freebroccolo/docker-haskell/issues/86

Any feedback on experience with Haskell in Docker? My feeling is that Haskellers doesn't use it too much... Am I wrong?

Corentin

[Michael Snoyman]

I use Docker extensively in Haskell projects, both for builds and deployments. We do this for most work at FP Complete as well, and most of our clients do too. The issue you're running into is that you're using a Haskell _build_ image (which includes GHC and other build tools) for creating a runtime image. My recommendation: based your deployment on a much more lightweight image. You can start off with Ubuntu, for example, or fpco/pid1:18.04 (which includes a more intelligent pid-1 process). Some people will argue that you should try to use something more minimal, and/or try to do static linking. I think starting off with Ubuntu is perfectly reasonable.

Some relevant blog posts:

* https://www.fpcomplete.com/blog/2017/12/building-haskell-apps-with-docker

* https://www.fpcomplete.com/blog/2016/10/static-compilation-with-stack

* https://www.fpcomplete.com/blog/2018/07/deploying-rust-with-docker-and-kubernetes (Rust instead of Haskell, the ideas translate)

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[Corentin Dupont]

Hi Michael,

thanks for the reply.

I'm trying to create Dockerfiles for reproducible builds. I have a platform with components written in various languages, so I don't expect users to install all build tools to compile... So I strive to provide Dockerfiles that manage both compilation and deployment.

Maybe it's a misunderstanding on my side to try to get both compilation and deployement in the same Dockerfile?

Thanks a lot.

[Corentin Dupont]

I just found out I could use multi-stage builds to solve my problem: https://docs.docker.com/develop/develop-images/multistage-build/

The idea is to use the command "FROM" again after building...