[Question] Docker multi-stage builds with Bazel

[corradio]

Hi,

I'm looking for best practices to build a nodejs Docker container using Bazel.
Ideally I would use a two-stage docker build (first to build node modules + compile, second to add the compiled assets). However, I can't find how to do that using Bazel.
Is this possible?

Best,

Olivier

[mattmoor]

@dlorenc @alexeagle FYI

tl;dr There isn't a good story today, but I'd like one.

Today rules_nodejs requires you to npm install (or equivalent) to create the node_modules directory in-tree, and it isn't clear to me that the way node_binary is set up is suitable for use by rules_docker as a lang_image rule (I need to poke around the runfiles and see; I don't believe Node.js has a mono-archive form like PAR we can use as a stand-in).

In my idealized world, containerizing a Node.js application with Bazel would be as simple as rewriting node_binary with node_image, but that isn't where we're at for (at least) Node.js today.

[corradio]

Thanks for your fast answer. I was indeed looking at a similar solution.
My only worry is that by creating node_modules outside of the containerised environment, the native version of the modules would not be used if the blaze platform (e.g. Mac OS) is different from the container platform (e.g. Linux Ubuntu).
I wasn't able to find more documentation about the way native modules are compiled through npm in node.

Happy to contribute if we see a clear way forward.

[mattmoor]

@corradio Yes, although it is not clear to me that there is any good "cross-installation" story for any of the common package managers (e.g. npm, pip, ...), which is what we'd need to achieve this in Bazel without remote execution (where you'd actually run it on the target environment).

I think that there are two tiers of this:

1. Get this working for node_binary to node_image.
2. Get node_binary working for cross-compilation (a la cross-installation).

If there is a story for cross-installation in npm I think it makes a strong argument for moving package installation into a repository_rule that is sensitive to the target Platform.

[mattmoor]

I tried out the Dropbox rules_node, but hit a few issues (1, 2).

Trying out bazelbuild/rules_nodejs it took me a while to make sense of their samples, but I was able to get something super trivial working (as I could with Dropbox), but not with node_modules (see here).

[mattmoor]

So I have a basic npm_install rule working here with bazelbuild/rules_nodejs and on top of these I was able to get a nodejs_image rule working on top of bazelbuild/rules_docker, but only with gcr.io/google-appengine/nodejs and not gcr.io/distroless/nodejs.

The reason for this is that the entrypoint that bazelbuild/rules_nodejs creates is a bash script, so it doesn't even seem to work on gcr.io/distroless/nodejs:debug.

I'll keep looking at this, but that seems like good progress :)

[corradio]

Great! I'm quite busy in the next days but will try to help out as soon as I have a bit of time.

[mattmoor]

If you have a chance to check it out here's the PR: bazelbuild/rules_docker#254

It is based on a couple PRs that need to land elsewhere (thus WiP), but I'd appreciate a second opinion on its readiness :)

thanks.

[dlorenc]

Is this still relevant?

[chanseokoh]

Closing as the question seems obsolete now.