Docker RUN used in Cloud documentation.

[jackwootton]

Google's documentation for Building a Docker Image makes use of RUN:

FROM gcr.io/google_appengine/python

RUN apt-get update && \
    apt-get install -y python2.7 python-pip && \
    apt-get clean && \
    rm /var/lib/apt/lists/*_*

ADD . /app
WORKDIR /app

RUN pip install -r requirements.txt
ENTRYPOINT ["gunicorn", "-b", ":8080", "main:app"]

Sample Dockerfile at python-docs-samples/endpoints/getting-started/Dockerfile.custom.

I've read through Supporting RUN instructions? - but it remains unclear to me how this works with pip install.

[mattmoor]

(to rehash that thread a little bit)
The way Bazel builds Docker images is fundamentally different from the way just about everyone else builds Docker images. In particular, we don't support RUN because of two main reasons:

1. Virtually everything folks do in RUN isn't reproducible.
2. The way the Docker daemon evaluates RUN is never reproducible.

This can be a bit of a pill for folks used to Dockerfile's convenience, but if you can manage to live within these constraints you get a ton of nice properties that are virtually impossible with traditional methods. These properties (and constraints) are largely projections of Bazel's principles.

---

Your real question seems to be: How do I make my Bazel application consume PIP dependencies?

That is a great question, and a useful feature independent of its use in Docker images! I recently put together bazelbuild/rules_python to solve this looooooong-standing Bazel issue (in part because it was such a common ask from rules_docker users).

I think you'd be interested in seeing this example. It combines bazelbuild/rules_python to import PIP dependencies into Bazel, and then assembles a Python image using py_image from this repository.

The reason the sample isn't merged is because of this issue, which has a pretty straightforward workaround.

[fikriauliya]

@mattmoor I have seen your example, please correct me if my understanding is incorrect:

• You run pip install in the host environment (in WORKSPACE)
• The generated files are included into docker image via deps param
• This way, we don't need RUN instruction as in Dockerfile

I have similar cases to run npm install and bundle install. Those are currently run in my Dockerfile. Learning from your approach, can I simple run npm install and bundle install in the host (in WORKSPACE) and copy the downloaded dependencies (packages folder in the case of npm install) to Docker via deps?

[mattmoor]

rules_nodejs has an npm_install that works similarly to pip_install. I'm not familiar with bundle install?

[fikriauliya]

bundle install is to install Ruby dependency. Since it's not yet supported, I am thinking to create myself.
Any article/sample code to the recommended way to install external dependencies not managed by Bazel (e.g. pip, npm)? Or are my points above sufficiently correct?