CONTRIBUTING.md

Contribute to the Buildx project

This page contains information about reporting issues as well as some tips and guidelines useful to experienced open source contributors.

Reporting security issues

The project maintainers take security seriously. If you discover a security issue, please bring it to their attention right away!

Please DO NOT file a public issue, instead send your report privately to security@docker.com.

Security reports are greatly appreciated and we will publicly thank you for it. We also like to send gifts—if you're into schwag, make sure to let us know. We currently do not offer a paid security bounty program, but are not ruling it out in the future.

Reporting other issues

A great way to contribute to the project is to send a detailed report when you encounter an issue. We always appreciate a well-written, thorough bug report, and will thank you for it!

Check that our issue database doesn't already include that problem or suggestion before submitting an issue. If you find a match, you can use the "subscribe" button to get notified on updates. Do not leave random "+1" or "I have this too" comments, as they only clutter the discussion, and don't help resolving it. However, if you have ways to reproduce the issue or have additional information that may help resolving the issue, please leave a comment.

Include the steps required to reproduce the problem if possible and applicable. This information will help us review and fix your issue faster. When sending lengthy log-files, consider posting them as an attachment, instead of posting inline.

Do not forget to remove sensitive data from your logfiles before submitting (you can replace those parts with "REDACTED").

Pull requests are always welcome

Not sure if that typo is worth a pull request? Found a bug and know how to fix it? Do it! We will appreciate it.

If your pull request is not accepted on the first try, don't be discouraged! If there's a problem with the implementation, hopefully you received feedback on what to improve.

We're trying very hard to keep Buildx lean and focused. We don't want it to do everything for everybody. This means that we might decide against incorporating a new feature. However, there might be a way to implement that feature on top of Buildx.

Design and cleanup proposals

You can propose new designs for existing features. You can also design entirely new features. We really appreciate contributors who want to refactor or otherwise cleanup our project.

Sign your work

The sign-off is a simple line at the end of the explanation for the patch. Your signature certifies that you wrote the patch or otherwise have the right to pass it on as an open-source patch. The rules are pretty simple: if you can certify the below (from developercertificate.org):

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

Then you just add a line to every git commit message:

Signed-off-by: Joe Smith <joe.smith@email.com>

Use your real name (sorry, no pseudonyms or anonymous contributions.)

If you set your user.name and user.email git configs, you can sign your commit automatically with git commit -s.

Run the unit- and integration-tests

Running tests:

make test

This runs all unit and integration tests, in a containerized environment. Locally, every package can be tested separately with standard Go tools, but integration tests are skipped if local user doesn't have enough permissions or worker binaries are not installed.

# run unit tests only
make test-unit

# run integration tests only
make test-integration

# test a specific package
TESTPKGS=./bake make test

# run all integration tests with a specific worker
TESTFLAGS="--run=//worker=remote -v" make test-integration

# run a specific integration test
TESTFLAGS="--run /TestBuild/worker=remote/ -v" make test-integration

# run a selection of integration tests using a regexp
TESTFLAGS="--run /TestBuild.*/worker=remote/ -v" make test-integration

Note

Set TEST_KEEP_CACHE=1 for the test framework to keep external dependant images in a docker volume if you are repeatedly calling make test. This helps to avoid rate limiting on the remote registry side.

Note

Set TEST_DOCKERD=1 for the test framework to enable the docker workers, specifically the docker and docker-container drivers.

The docker tests cannot be run in parallel, so require passing --parallel=1 in TESTFLAGS.

Note

If you are working behind a proxy, you can set some of or all HTTP_PROXY=http://ip:port, HTTPS_PROXY=http://ip:port, NO_PROXY=http://ip:port for the test framework to specify the proxy build args.

Run the helper commands

To enter a demo container environment and experiment, you may run:

$ make shell

To validate PRs before submitting them you should run:

$ make validate-all

To generate new vendored files with go modules run:

$ make vendor

Generate profiling data

You can configure Buildx to generate pprof memory and CPU profiles to analyze and optimize your builds. These profiles are useful for identifying performance bottlenecks, detecting memory inefficiencies, and ensuring the program (Buildx) runs efficiently.

The following environment variables control whether Buildx generates profiling data for builds:

$ export BUILDX_CPU_PROFILE=buildx_cpu.prof
$ export BUILDX_MEM_PROFILE=buildx_mem.prof

When set, Buildx emits profiling samples for the builds to the location specified by the environment variable.

To analyze and visualize profiling samples, you need pprof from the Go toolchain, and (optionally) GraphViz for visualization in a graphical format.

To inspect profiling data with pprof:

1. Build a local binary of Buildx from source.

   $ docker buildx bake

   The binary gets exported to ./bin/build/buildx.

2. Run a build and with the environment variables set to generate profiling data.

   $ export BUILDX_CPU_PROFILE=buildx_cpu.prof
   $ export BUILDX_MEM_PROFILE=buildx_mem.prof
   $ ./bin/build/buildx bake

   This creates buildx_cpu.prof and buildx_mem.prof for the build.

3. Start pprof and specify the filename of the profile that you want to analyze.

   $ go tool pprof buildx_cpu.prof

   This opens the pprof interactive console. From here, you can inspect the profiling sample using various commands. For example, use top 10 command to view the top 10 most time-consuming entries.

   (pprof) top 10
   Showing nodes accounting for 3.04s, 91.02% of 3.34s total
   Dropped 123 nodes (cum <= 0.02s)
   Showing top 10 nodes out of 159
         flat  flat%   sum%        cum   cum%
        1.14s 34.13% 34.13%      1.14s 34.13%  syscall.syscall
        0.91s 27.25% 61.38%      0.91s 27.25%  runtime.kevent
        0.35s 10.48% 71.86%      0.35s 10.48%  runtime.pthread_cond_wait
        0.22s  6.59% 78.44%      0.22s  6.59%  runtime.pthread_cond_signal
        0.15s  4.49% 82.93%      0.15s  4.49%  runtime.usleep
        0.10s  2.99% 85.93%      0.10s  2.99%  runtime.memclrNoHeapPointers
        0.10s  2.99% 88.92%      0.10s  2.99%  runtime.memmove
        0.03s   0.9% 89.82%      0.03s   0.9%  runtime.madvise
        0.02s   0.6% 90.42%      0.02s   0.6%  runtime.(*mspan).typePointersOfUnchecked
        0.02s   0.6% 91.02%      0.02s   0.6%  runtime.pcvalue
   

To view the call graph in a GUI, run go tool pprof -http=:8081 <sample>.

Note

Requires GraphViz to be installed.

$ go tool pprof -http=:8081 buildx_cpu.prof
Serving web UI on http://127.0.0.1:8081
http://127.0.0.1:8081

For more information about using pprof and how to interpret the call graph, refer to the pprof README.

Conventions

• Fork the repository and make changes on your fork in a feature branch
• Submit tests for your changes. See run the unit- and integration-tests for details.
• Sign your work

Write clean code. Universally formatted code promotes ease of writing, reading, and maintenance. Always run gofmt -s -w file.go on each changed file before committing your changes. Most editors have plug-ins that do this automatically.

Pull request descriptions should be as clear as possible and include a reference to all the issues that they address. Be sure that the commit messages also contain the relevant information.

Successful Changes

Before contributing large or high impact changes, make the effort to coordinate with the maintainers of the project before submitting a pull request. This prevents you from doing extra work that may or may not be merged.

Large PRs that are just submitted without any prior communication are unlikely to be successful.

While pull requests are the methodology for submitting changes to code, changes are much more likely to be accepted if they are accompanied by additional engineering work. While we don't define this explicitly, most of these goals are accomplished through communication of the design goals and subsequent solutions. Often times, it helps to first state the problem before presenting solutions.

Typically, the best methods of accomplishing this are to submit an issue, stating the problem. This issue can include a problem statement and a checklist with requirements. If solutions are proposed, alternatives should be listed and eliminated. Even if the criteria for elimination of a solution is frivolous, say so.

Larger changes typically work best with design documents. These are focused on providing context to the design at the time the feature was conceived and can inform future documentation contributions.

Commit Messages

Commit messages must start with a capitalized and short summary (max. 50 chars) written in the imperative, followed by an optional, more detailed explanatory text which is separated from the summary by an empty line.

Commit messages should follow best practices, including explaining the context of the problem and how it was solved, including in caveats or follow up changes required. They should tell the story of the change and provide readers understanding of what led to it.

If you're lost about what this even means, please see How to Write a Git Commit Message for a start.

In practice, the best approach to maintaining a nice commit message is to leverage a git add -p and git commit --amend to formulate a solid changeset. This allows one to piece together a change, as information becomes available.

If you squash a series of commits, don't just submit that. Re-write the commit message, as if the series of commits was a single stroke of brilliance.

That said, there is no requirement to have a single commit for a PR, as long as each commit tells the story. For example, if there is a feature that requires a package, it might make sense to have the package in a separate commit then have a subsequent commit that uses it.

Remember, you're telling part of the story with the commit message. Don't make your chapter weird.

Review

Code review comments may be added to your pull request. Discuss, then make the suggested modifications and push additional commits to your feature branch. Post a comment after pushing. New commits show up in the pull request automatically, but the reviewers are notified only when you comment.

Pull requests must be cleanly rebased on top of master without multiple branches mixed into the PR.

Git tip: If your PR no longer merges cleanly, use rebase master in your feature branch to update your pull request rather than merge master.

Before you make a pull request, squash your commits into logical units of work using git rebase -i and git push -f. A logical unit of work is a consistent set of patches that should be reviewed together: for example, upgrading the version of a vendored dependency and taking advantage of its now available new feature constitute two separate units of work. Implementing a new function and calling it in another file constitute a single logical unit of work. The very high majority of submissions should have a single commit, so if in doubt: squash down to one.

• After every commit, make sure the test suite passes. Include documentation changes in the same pull request so that a revert would remove all traces of the feature or fix.
• Include an issue reference like closes #XXXX or fixes #XXXX in the PR description that close an issue. Including references automatically closes the issue on a merge.
• Do not add yourself to the AUTHORS file, as it is regenerated regularly from the Git history.
• See the Coding Style for further guidelines.

Merge approval

Project maintainers use LGTM (Looks Good To Me) in comments on the code review to indicate acceptance, or use the Github review approval feature.

Coding Style

Unless explicitly stated, we follow all coding guidelines from the Go community. While some of these standards may seem arbitrary, they somehow seem to result in a solid, consistent codebase.

It is possible that the code base does not currently comply with these guidelines. We are not looking for a massive PR that fixes this, since that goes against the spirit of the guidelines. All new contributions should make a best effort to clean up and make the code base better than they left it. Obviously, apply your best judgement. Remember, the goal here is to make the code base easier for humans to navigate and understand. Always keep that in mind when nudging others to comply.

The rules:

1. All code should be formatted with gofmt -s.
2. All code should pass the default levels of golint.
3. All code should follow the guidelines covered in Effective Go and Go Code Review Comments.
4. Comment the code. Tell us the why, the history and the context.
5. Document all declarations and methods, even private ones. Declare expectations, caveats and anything else that may be important. If a type gets exported, having the comments already there will ensure it's ready.
6. Variable name length should be proportional to its context and no longer. noCommaALongVariableNameLikeThisIsNotMoreClearWhenASimpleCommentWouldDo. In practice, short methods will have short variable names and globals will have longer names.
7. No underscores in package names. If you need a compound name, step back, and re-examine why you need a compound name. If you still think you need a compound name, lose the underscore.
8. No utils or helpers packages. If a function is not general enough to warrant its own package, it has not been written generally enough to be a part of a util package. Just leave it unexported and well-documented.
9. All tests should run with go test and outside tooling should not be required. No, we don't need another unit testing framework. Assertion packages are acceptable if they provide real incremental value.
10. Even though we call these "rules" above, they are actually just guidelines. Since you've read all the rules, you now know that.

If you are having trouble getting into the mood of idiomatic Go, we recommend reading through Effective Go. The Go Blog is also a great resource.