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Contributing

Thank you for your interest in contributing to Tendermint! Before contributing, it may be helpful to understand the goal of the project. The goal of Tendermint 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 Tendermint project or a potential fork. When targeting the main Tendermint project, the following process leads to the best chance of landing changes in main.

All 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.

All new contributions should start with a Github Issue. The issue helps capture the problem you're trying to solve and allows for early feedback. 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.

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

When the problem is well understood but the solution leads to large 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.

How to pick a number for the ADR?

Find the largest existing ADR number and bump it by 1.

When the problem as well as proposed solution are well understood, changes should start with a draft pull request against main. The draft signals that work is underway. When the work is ready for feedback, hitting "Ready for Review" will signal to the maintainers to take a look.

Contributing flow

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.

Forking

Please note that Go requires code to live under absolute paths, which complicates forking. While my fork lives at https://github.com/ebuchman/tendermint, the code should never exist at $GOPATH/src/github.com/ebuchman/tendermint. Instead, we use git remote to add the fork as a new remote for the original repo, $GOPATH/src/github.com/tendermint/tendermint, 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/tendermint/tendermint)
  • git remote rename origin upstream
  • git remote add origin git@github.com:ebuchman/basecoin.git

Now origin refers to my fork and upstream refers to the Tendermint version. So I can git push -u origin main to update my fork, and make pull requests to tendermint 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 Tendermint 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, eg. GO111MODULE=on go get -u github.com/tendermint/go-amino@master.

Protobuf

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

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 in proto/tendermint
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 in proto/tendermint
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

Every fix, improvement, feature, or breaking change should be made in a pull-request that includes an update to the CHANGELOG_PENDING.md file.

A feature can also be worked on a feature branch, if its size and/or risk justifies it (see #branching-model-and-release) 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 Tendermint 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/tendermint/tendermint, or your fork (using git remote add origin).

Make changes, and before submitting a pull request, update the CHANGELOG_PENDING.md 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, Tendermint-based blockchain, light client, wallet).

Once you have submitted a pull request label the pull request with either R:minor, if the change should be included in the next minor release, or R:major, if the change is meant for a major release.

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 Tendermint 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 Tendermint network.

See README for details.

Run:

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

Model-based tests (ADVANCED)

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

For components, that have been formally verified using TLA+, it may be possible to generate tests using a combination of the Apalache Model Checker and tendermint-rs testgen util.

Now, I know there's a lot to take in. If you want to learn more, check out this video by Andrey Kupriyanov & Igor Konnov.

At the moment, we have model-based tests for the light client, located in the ./light/mbt directory.

Run: cd light/mbt && go test

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}

Jepsen tests (ADVANCED)

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

Jepsen tests are used to verify the linearizability property of the Tendermint consensus. They are located in a separate repository -> https://github.com/tendermint/jepsen. Please refer to its README for more information.

RPC Testing

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

To test your changes you must install nodejs and run:

npm i -g dredd
make build-linux build-contract-tests-hooks
make contract-tests

WARNING: these are currently broken due to https://github.com/apiaryio/dredd not supporting complete OpenAPI 3.

This command will popup a network and check every endpoint against what has been documented.