[maccard]

I’m inclined to agree with you about not building containers. That said, I find myself going around in circles. We have an app that uses a specific toolchain version, how do we install that version on a build machine without requiring an SRE ticket to update our toolchain?

Containers nicely solve this problem. Then your builds get a little slow, so you want to cache things. Now your docker file looks like this. You want to run some tests - now it’s even more complicated. How do you debug those tests? How do those tests communicate with external systems (database/redis). Eventually you end up back at “let’s just containerise the packaging”.

[cogman10]

You can mount the current directory into docker and run an image of your tool.

Here's an example of that from the docker maven.

`docker run -it --rm --name my-maven-project -v "$(pwd)":/usr/src/mymaven -w /usr/src/mymaven maven:3.3-jdk-8 mvn clean install`

You can get as fancy as you like with things like your `.m2` directory, this just gives you the basics of how you'd do that.

[maccard]

Thanks - this is an interesting idea I had never considered. I do like the layer based caching of dockerfiles, which you give up entirely for this but it allows for things like running containerised builds cached SCM checkouts (our repository is 300GB…)

[cogman10]

Yeah, it's basically tradeoffs all around.

The benefit of this approach is it's a lot easier to make sure dependencies end up on the build node so you aren't redownloading and caching the same dependency for multiple artifacts. But then you don't get to take advantage of docker build caching to speed up things when something doesn't change.

That's the part about docker I don't love. I get why it's this way, but I wish there was a better way to have it reuse files between images. The best you can do is a cache mount. But that can run into size issues as time goes on which is annoying.

[pstuart]

Depending on how the container is structured, you could have the original container as a baseline default, and then have "enhanced" containers that use it as a base and overlay the caching and other errata to serve that specialized need.

[maccard]

I’ve tried this in the past, but it pushes the dependency management pf the layers into whatever is orchestrating the container build, as opposed to multi stage builds which will parallelise!

Not dismissing, but it’s just caveats every which way. I think in an ideal world I just want Bazel or Nixos without the baggage that comes with them - docker comes so close but yet falls so short of the finish line.