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Contributing

Thank you for your interest in contributing to CometBFT! Before contributing, it may be helpful to understand the goal of the project. The goal of CometBFT is to develop a BFT consensus engine robust enough to support permissionless value-carrying networks. While all contributions are welcome, contributors should bear this goal in mind in deciding if they should target the main CometBFT project or a potential fork.

Overview

When targeting the main CometBFT project, following the processes outlined in this document will lead to the best chance of landing changes in a release.

Core team responsibility

The CometBFT core team is responsible for stewarding this project over time. This means that the core team needs to understand the nature of, and agree to maintain, all of the changes that land on main or a backport branch. It may cost a few days/weeks' worth of time to submit a particular change, but maintaining that change over the years has a much higher cost that the core team will bear.

Ease of reviewing

The fact that the core team needs to be able to deeply understand the short-, medium- and long-term consequences of incoming changes means that changes need to be easily reviewed.

What makes a change easy to review, and more likely to land in an upcoming release?

  1. Each pull request must do one thing. It must be very clear what that one thing is when looking at the pull request title, description, and linked issues. It must also be very clear what value it ultimately aims to deliver, and to which user(s). A single pull request that does multiple things, or without a clear articulation of the problem it attempts to solve, may be rejected immediately.

  2. Each pull request must be at most 300 lines of code changes. Larger changes must be structured as a series of pull requests of at most 300 lines of code changes each, each building upon the previous one, all ideally tracked in a tracking issue.

    If a single PR absolutely has to be larger, it must be structured such that it can be reviewed commit by commit, with each commit doing one logical thing (with a good description of what it aims to achieve in the Git commit), and each commit ideally being no larger than 300 lines of code changes. Poorly structured pull requests may be rejected immediately with a request to restructure them.

    This does not necessarily apply to documentation-related changes or automatically generated code (e.g. generated from Protobuf definitions). But automatically generated code changes should occur within separate commits, so they are easily distinguishable from manual code changes.

Workflow

The following diagram summarizes the general workflow used by the core team to make changes, with a full description of the workflow below the diagram. Exceptions to this process will naturally occur (e.g. in the case of urgent security fixes), but this is rare.

Each stage of the process is aimed at creating feedback cycles which align contributors and maintainers to make sure:

  • Contributors don’t waste their time implementing/proposing features which won't land in main.
  • Maintainers have the necessary context in order to support and review contributions.
flowchart LR
    complexity{Problem\ncomplexity}
    issue("New issue\n(Problem articulation\nfor discussion)")
    clarity{"Problem +\nsolution clarity"}
    rfc("RFC pull request(s)")
    rfc_merge("Merge RFC to main")
    risk{"Solution\ncomplexity/risk"}
    adr("ADR + PoC\npull request(s)")
    adr_merge("Merge ADR to main\nand create tracking issue")
    pr("Solution\npull request(s)")
    merge("Merge to main/backport\nor feature branch")

    complexity --"Low/Moderate/High"--> issue
    complexity --Trivial--> pr
    issue --> clarity
    clarity --High--> risk
    clarity --Low--> rfc
    rfc --Approved--> rfc_merge
    risk --"Moderate/High"--> adr
    adr --"ADR accepted by core team"--> adr_merge
    adr_merge --> pr
    risk --Low--> pr
    pr --Approved--> merge
Loading

GitHub issues

All non-trivial work on the code base should be motivated by a GitHub Issue. Search is a good place to start when looking for places to contribute. If you would like to work on an issue which already exists, please indicate so by leaving a comment. If someone else is already assigned to that issue and you would like to contribute to it or take it over, please coordinate with the existing assignee(s) and only start work on it once you have been assigned to it. Unsolicited pull requests relating to issues assigned to other users may be rejected immediately.

All new contributions should start with a GitHub Issue. The issue helps capture the problem being solved and allows for early feedback. Problems must be captured in terms of the impact that they have on specific users. Once the issue is created the process can proceed in different directions depending on how well defined the problem and potential solution are. If the change is simple and well understood, maintainers will indicate their support with a heartfelt emoji.

Request for comments (RFCs)

If the issue would benefit from thorough discussion, maintainers may request that you create a Request For Comment in the CometBFT repo. Discussion at the RFC stage will build collective understanding of the dimensions of the problems and help structure conversations around trade-offs.

Architecture decision records (ADRs)

When the problem is well understood but the solution leads to large/complex/risky structural changes to the code base, these changes should be proposed in the form of an Architectural Decision Record (ADR). The ADR will help build consensus on an overall strategy to ensure the code base maintains coherence in the larger context. If you are not comfortable with writing an ADR, you can open a less-formal issue and the maintainers will help you turn it into an ADR. Sometimes the best way to demonstrate the value of an ADR is to build a proof-of-concept (PoC) along with the ADR - in this case, link to the PoC from the ADR PR.

How does one pick a number for an new ADR?

Find the largest existing ADR number (between those in ./docs/architecture/ and those that may be open as issues or pull requests) and bump it by 1.

Pull requests

When the problem as well as proposed solution are well understood and low-risk, changes should start with a pull request.

Please adhere to the guidelines in the Ease of reviewing section above when submitting pull requests.

Draft pull requests

One can optionally submit a draft pull request against main, in which case this signals that work is underway and is not ready for review. Only users that are familiar with the issue, or those that the author explicitly requested a review from are expected to write comments at this point. When the work is ready for feedback, hitting "Ready for Review" will signal to the maintainers to take a look, and to the rest of the community that feedback is welcome.

The team may opt to ignore unsolicited comments/feedback on draft PRs, as having to respond to feedback on work that is not marked as "Ready for Review" interferes with the process of getting the work to the point that it is ready to review.

Forking

Please note that Go requires code to live under absolute paths, which complicates forking. While my fork lives at https://github.com/ebuchman/cometbft, the code should never exist at $GOPATH/src/github.com/ebuchman/cometbft. Instead, we use git remote to add the fork as a new remote for the original repo, $GOPATH/src/github.com/cometbft/cometbft, and do all the work there.

For instance, to create a fork and work on a branch of it, I would:

  • Create the fork on GitHub, using the fork button.
  • Go to the original repo checked out locally (i.e. $GOPATH/src/github.com/cometbft/cometbft)
  • git remote rename origin upstream
  • git remote add origin [email protected]:ebuchman/basecoin.git

Now origin refers to my fork and upstream refers to the CometBFT version. So I can git push -u origin main to update my fork, and make pull requests to CometBFT from there. Of course, replace ebuchman with your git handle.

To pull in updates from the origin repo, run

  • git fetch upstream
  • git rebase upstream/main (or whatever branch you want)

Dependencies

We use Go modules to manage dependencies.

That said, the main branch of every CometBFT repository should just build with go get, which means they should be kept up-to-date with their dependencies so we can get away with telling people they can just go get our software.

Since some dependencies are not under our control, a third party may break our build, in which case we can fall back on go mod tidy. Even for dependencies under our control, go helps us to keep multiple repos in sync as they evolve. Anything with an executable, such as apps, tools, and the core, should use dep.

Run go list -u -m all to get a list of dependencies that may not be up-to-date.

When updating dependencies, please only update the particular dependencies you need. Instead of running go get -u=patch, which will update anything, specify exactly the dependency you want to update.

Protobuf

We use Protocol Buffers along with gogoproto to generate code for use across CometBFT.

To generate proto stubs, lint, and check protos for breaking changes, you will need to install buf and gogoproto. Then, from the root of the repository, run:

# Lint all of the .proto files
make proto-lint

# Check if any of your local changes (prior to committing to the Git repository)
# are breaking
make proto-check-breaking

# Generate Go code from the .proto files
make proto-gen

To automatically format .proto files, you will need clang-format installed. Once installed, you can run:

make proto-format

Visual Studio Code

If you are a VS Code user, you may want to add the following to your .vscode/settings.json:

{
  "protoc": {
    "options": [
      "--proto_path=${workspaceRoot}/proto",
    ]
  }
}

Changelog

To manage and generate our changelog, we currently use unclog.

Every fix, improvement, feature, or breaking change should be made in a pull-request that includes a file .changelog/unreleased/${category}/${issue-or-pr-number}-${description}.md, where:

  • category is one of improvements, breaking-changes, bug-fixes, features and if multiple apply, create multiple files;
  • description is a short (4 to 6 word), hyphen separated description of the fix, starting the component changed; and,
  • issue or PR number is the CometBFT issue number, if one exists, or the PR number, otherwise.

For examples, see the .changelog folder.

A feature can also be worked on a feature branch, if its size and/or risk justifies it (see below).

What does a good changelog entry look like?

Changelog entries should answer the question: "what is important about this change for users to know?" or "what problem does this solve for users?". It should not simply be a reiteration of the title of the associated PR, unless the title of the PR very clearly explains the benefit of a change to a user.

Some good examples of changelog entry descriptions:

- [consensus] \#1111 Small transaction throughput improvement (approximately
  3-5\% from preliminary tests) through refactoring the way we use channels
- [mempool] \#1112 Refactor Go API to be able to easily swap out the current
  mempool implementation in CometBFT forks
- [p2p] \#1113 Automatically ban peers when their messages are unsolicited or
  are received too frequently

Some bad examples of changelog entry descriptions:

- [consensus] \#1111 Refactor channel usage
- [mempool] \#1112 Make API generic
- [p2p] \#1113 Ban for PEX message abuse

For more on how to write good changelog entries, see:

Changelog entry format

Changelog entries should be formatted as follows:

- [module] \#xxx Some description of the change (@contributor)

Here, module is the part of the code that changed (typically a top-level Go package), xxx is the pull-request number, and contributor is the author/s of the change.

It's also acceptable for xxx to refer to the relevant issue number, but pull-request numbers are preferred. Note this means pull-requests should be opened first so the changelog can then be updated with the pull-request's number. There is no need to include the full link, as this will be added automatically during release. But please include the backslash and pound, eg. \#2313.

Changelog entries should be ordered alphabetically according to the module, and numerically according to the pull-request number.

Changes with multiple classifications should be doubly included (eg. a bug fix that is also a breaking change should be recorded under both).

Breaking changes are further subdivided according to the APIs/users they impact. Any change that affects multiple APIs/users should be recorded multiply - for instance, a change to the Blockchain Protocol that removes a field from the header should also be recorded under CLI/RPC/Config since the field will be removed from the header in RPC responses as well.

Branching Model and Release

The main development branch is main.

Every release is maintained in a release branch named vX.Y.Z.

Pending minor releases have long-lived release candidate ("RC") branches. Minor release changes should be merged to these long-lived RC branches at the same time that the changes are merged to main.

If a feature's size is big and/or its risk is high, it can be implemented in a feature branch. While the feature work is in progress, pull requests are open and squash merged against the feature branch. Branch main is periodically merged (merge commit) into the feature branch, to reduce branch divergence. When the feature is complete, the feature branch is merged back (merge commit) into main. The moment of the final merge can be carefully chosen so as to land different features in different releases.

Note, all pull requests should be squash merged except for merging to a release branch (named vX.Y). This keeps the commit history clean and makes it easy to reference the pull request where a change was introduced.

Development Procedure

The latest state of development is on main, which must never fail make test. Never force push main, unless fixing broken git history (which we rarely do anyways).

To begin contributing, create a development branch either on github.com/cometbft/cometbft, or your fork (using git remote add origin).

Make changes, and before submitting a pull request, update the changelog to record your change. Also, run either git rebase or git merge on top of the latest main. (Since pull requests are squash-merged, either is fine!)

Update the UPGRADING.md if the change you've made is breaking and the instructions should be in place for a user on how he/she can upgrade its software (ABCI application, CometBFT blockchain, light client, wallet).

Sometimes (often!) pull requests get out-of-date with main, as other people merge different pull requests to main. It is our convention that pull request authors are responsible for updating their branches with main. (This also means that you shouldn't update someone else's branch for them; even if it seems like you're doing them a favor, you may be interfering with their git flow in some way!)

Merging Pull Requests

It is also our convention that authors merge their own pull requests, when possible. External contributors may not have the necessary permissions to do this, in which case, a member of the core team will merge the pull request once it's been approved.

Before merging a pull request:

  • Ensure pull branch is up-to-date with a recent main (GitHub won't let you merge without this!)
  • Run make test to ensure that all tests pass
  • Squash merge pull request

Pull Requests for Minor Releases

If your change should be included in a minor release, please also open a PR against the long-lived minor release candidate branch (e.g., rc1/v0.33.5) immediately after your change has been merged to main.

You can do this by cherry-picking your commit off main:

$ git checkout rc1/v0.33.5
$ git checkout -b {new branch name}
$ git cherry-pick {commit SHA from main}
# may need to fix conflicts, and then use git add and git cherry-pick --continue
$ git push origin {new branch name}

After this, you can open a PR. Please note in the PR body if there were merge conflicts so that reviewers can be sure to take a thorough look.

Git Commit Style

We follow the Go style guide on commit messages. Write concise commits that start with the package name and have a description that finishes the sentence "This change modifies CometBFT to...". For example,

cmd/debug: execute p.Signal only when p is not nil

[potentially longer description in the body]

Fixes #nnnn

Each PR should have one commit once it lands on main; this can be accomplished by using the "squash and merge" button on GitHub. Be sure to edit your commit message, though!

Testing

Unit tests

Unit tests are located in _test.go files as directed by the Go testing package. If you're adding or removing a function, please check there's a TestType_Method test for it.

Run: make test

Integration tests

Integration tests are also located in _test.go files. What differentiates them is a more complicated setup, which usually involves setting up two or more components.

Run: make test_integrations

End-to-end tests

End-to-end tests are used to verify a fully integrated CometBFT network.

See README for details.

Run:

cd test/e2e && \
  make && \
  ./build/runner -f networks/ci.toml

Fuzz tests (ADVANCED)

NOTE: if you're just submitting your first PR, you won't need to touch these most probably (99.9%).

Fuzz tests can be found inside the ./test/fuzz directory. See README.md for details.

Run: cd test/fuzz && make fuzz-{PACKAGE-COMPONENT}

RPC Testing

If you contribute to the RPC endpoints it's important to document your changes in the OpenAPI file.