Add back examples for archiving binaries and assembling Docker images

[mvukov]

No description provided.

[outrider-ksilva]

I'm investigating using Bazel for some ROS builds and this repo has been extremely helpful! I've been able to get builds to work for interfaces, libraries, and launch-files, but I have not been able to get the container_image example to work.

I just saw that you've started making updates to this repo again. Do you know if the examples for docker images will look similar to the previous examples using container_image, or do you think they'll use a different strategy like oci_image? Do you have a timeline when you think the examples will be re-added?

I'm still learning Bazel, but let me know if there's anything I can do to help implement or test these changes.

[mvukov]

Hi, indeed, the idea is to use https://github.com/bazel-contrib/rules_oci . It should be fairly straightforward to set up an example for creating a ROS app deployment image using e.g. https://github.com/aspect-build/bazel-examples/tree/main/oci_python_image. I'll try to add this soon. If you manage to put together an example before me, please open a PR. It can be even simpler than that mentioned example: we don't need to split the layers (that's an optimization). We could create a single layer and point out how to split layers for more efficiency.

[JohnRudolfLewis]

I started looking into this. Looking at the example you reference, it appears as though each project would need to create a py_layer.bzl or similar in their project. Wouldn't it be nice to reduce that code duplication and include a function in this library to do all the heavy lifting for the users?

[JohnRudolfLewis]

I found a solution that works. A bit of a hack, but it works. Also, no layering with this solution either.

I could not get rules_pkg:pkg_tar to package up the runfiles, they've removed (hidden private actually) the previously accessible but undocumented include_runfiles argument. I was hoping to be able to use that, plus their ability to create symlinks to package up my tar properly. But no.

I found aspect_bazel_lib:tar includes the runfiles, but they are arranged in such a way that roslaunch will fail:

RLException: Invalid roslaunch XML syntax: [Errno 2] No such file or directory: 'external/com_github_mvukov_rules_ros~/third_party/ros/roslaunch/roscore.xml'
The traceback for the exception was written to the log file

A symlink can fix the problem, but this rule does not have any provision to create the needed symlink.

But this is easily fixed. I added a run.sh script to create the missing symlink, cd into the proper directory, then run the launch command.

#!/bin/sh
ln -s /chatter/chatter_launch.runfiles /chatter/chatter_launch.runfiles/_main/external
cd /chatter/chatter_launch.runfiles/_main
/chatter/chatter_launch

Add the following to your MODULE.bazel

bazel_dep(name = "aspect_bazel_lib", version = "2.7.9")
bazel_dep(name = "rules_oci", version = "1.8.0")
archive_override(
    module_name = "rules_oci",
    strip_prefix = "rules_oci-e389ddeed00139eaec9ca24689fa71079725d8ab",
    urls = "https://github.com/bazel-contrib/rules_oci/archive/e389ddeed00139eaec9ca24689fa71079725d8ab.zip",
)
oci = use_extension("@rules_oci//oci:extensions.bzl", "oci")
oci.pull(
    name = "base-image",
    image = "public.ecr.aws/docker/library/python:3.10",
    platforms = ["linux/amd64"],
)
use_repo(oci, "base-image", "base-image_linux_amd64")

And then in your BUILD.bazel

load("@aspect_bazel_lib//lib:tar.bzl", "tar")
load(
    "@rules_oci//oci:defs.bzl", 
    "oci_image", 
    "oci_load"
)

tar(
    name = "chatter_tar",
    srcs = [":chatter_launch", "run.sh"],
)

oci_image(
    name = "chatter_oci_image",
    base = "@base-image",
    tars = [":chatter_tar"],
    cmd = ["/chatter/run.sh"]
)

oci_load(
    name = "chatter_oci_load",
    image = ":chatter_oci_image",
    repo_tags = ["chatter:latest"],
)

To generate the image:

bazel run //chatter:chatter_oci_load

And to run that image locally:

docker run -ti --rm chatter:latest

Too much of an ugly hack to publish a PR with this, but hope this helps someone.