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Contributing to TiKV

Thanks for your interest in contributing to TiKV! This document outlines some of the conventions on building, running, and testing TiKV, the development workflow, commit message formatting, contact points and other resources.

TiKV has many dependent repositories. If you need any help or mentoring getting started, understanding the codebase, or making a PR (or anything else really), please ask on Slack, or WeChat. If you don't know where to start, please click on the contributor icon below to get you on the right contributing path.

contribution-map

Building and setting up a development workspace

TiKV is mostly written in Rust, but has components written in C++ (RocksDB) and Go (gRPC). We are currently using the Rust nightly toolchain. To provide consistency, we use linters and automated formatting tools.

Prerequisites

To build TiKV you'll need to at least have the following installed:

  • git - Version control
  • rustup - Rust installer and toolchain manager
  • make - Build tool (run common workflows)
  • cmake - Build tool (required for gRPC)
  • awk - Pattern scanning/processing language

If you are targeting platforms other than x86_64 linux, you'll also need:

  • llvm and clang - Used to generate bindings for different platforms and build native libraries (required for grpcio, rocksdb).

Getting the repository

git clone https://github.com/tikv/tikv.git
cd tikv
# Future instructions assume you are in this directory

Configuring your Rust toolchain

rustup is the official toolchain manager for Rust, similar to rvm or rbenv from the Ruby world.

TiKV is pinned to a version of Rust using a rust-toolchain file. rustup and cargo will automatically use this file. We also use the rustfmt and clippy components, to install those:

rustup component add rustfmt
rustup component add clippy

Building and testing

TiKV includes a Makefile with common workflows, you can also use cargo, as you would in many other Rust projects.

At this point, you can build TiKV:

make build

During interactive development, you may prefer using cargo check, which will parse, borrow check, and lint your code, but not actually compile it:

cargo check --all

It is particularly handy alongside cargo-watch, which runs a command each time you change a file.

cargo install cargo-watch
cargo watch -s "cargo check --all"

When you're ready to test out your changes, use the dev task. It will format your codebase, build with clippy enabled, and run tests. This should run without failure before you create a PR. Unfortunately, some tests will fail intermittently and others don't pass on all platforms. If you're unsure, just ask!

make dev

You can run the test suite alone, or just run a specific test:

# Run the full suite
make test
# Run a specific test
cargo test --all $TESTNAME -- --nocapture

TiKV follows the Rust community coding style. We use Rustfmt and Clippy to automatically format and lint our code. Using these tools is checked in our CI. These are as part of make dev, you can also run them alone:

# Run Rustfmt
cargo fmt
# Run Clippy (note that some lints are ignored, so `cargo clippy` will give many false positives)
make clippy

See the style doc and the API guidelines for details on the conventions.

Please follow this style to make TiKV easy to review, maintain, and develop.

Build issues

To reduce compilation time, TiKV builds do not include full debugging information by default — release and bench builds include no debuginfo; dev and test builds include line numbers only. The easiest way to enable debuginfo is to precede build commands with RUSTFLAGS=-Cdebuginfo=1 (for line numbers), or RUSTFLAGS=-Cdebuginfo=2 (for full debuginfo). For example,

RUSTFLAGS=-Cdebuginfo=2 make dev
RUSTFLAGS=-Cdebuginfo=2 cargo build

When building with make, cargo will automatically use pipelined compilation to increase the parallelism of the build. To turn on pipelining while using cargo directly, set CARGO_BUILD_PIPELINING=true.

Running TiKV

To run TiKV as an actual key-value store, you will need to run it as a cluster (a cluster can have just one node, which is useful for testing). You can do this on a single machine or on multiple machines. You need to use PD to manage the cluster (even if there is just one node on a single machine). Instructions are in our docs (if you build TiKV from source, then you don't need to download the binary).

Configuration

Read our configuration guide to learn about various configuration options. There is also a configuration template.

Contribution flow

This is a rough outline of what a contributor's workflow looks like:

  • Create a Git branch from where you want to base your work. This is usually master.
  • Write code, add test cases, and commit your work (see below for message format).
  • Run tests and make sure all tests pass.
  • Push your changes to a branch in your fork of the repository and submit a pull request.
  • Your PR will be reviewed by two maintainers, who may request some changes.
    • Once you've made changes, your PR must be re-reviewed and approved.
    • If the PR becomes out of date, you can use GitHub's 'update branch' button.
    • If there are conflicts, you can rebase (or merge) and resolve them locally. Then force push to your PR branch. You do not need to get re-review just for resolving conflicts, but you should request re-review if there are significant changes.
  • Our CI system automatically tests all pull requests.
  • Our bot will merge your PR. It can be summoned by commenting /merge or adding the S: CanMerge label (requires tests to pass and two approvals. You might have to ask your reviewer to do this).

Thanks for your contributions!

Finding something to work on.

For beginners, we have prepared many suitable tasks for you. Checkout our Help Wanted issues for a list, in which we have also marked the difficulty level.

If you are planning something big, for example, relates to multiple components or changes current behaviors, make sure to open an issue to discuss with us before going on.

The TiKV team actively develops and maintains a bunch of dependencies used in TiKV, which you may be also interested in:

  • rust-prometheus: The Prometheus client for Rust, our metrics collecting and reporting library
  • rust-rocksdb: Our RocksDB binding and wrapper for Rust
  • raft-rs: The Raft distributed consensus algorithm implemented in Rust
  • grpc-rs: The gRPC library for Rust built on the gRPC C Core library and Rust Futures
  • fail-rs: Fail points for Rust

Format of the commit message

We follow a rough convention for commit messages that is designed to answer two questions: what changed and why. The subject line should feature the what and the body of the commit should describe the why.

engine/raftkv: add comment for variable declaration.

Improve documentation.

The format can be described more formally as follows:

<subsystem>: <what changed>
<BLANK LINE>
<why this change was made>
<BLANK LINE>
Signed-off-by: <Name> <email address>

The first line is the subject and should be no longer than 50 characters, the other lines should be wrapped at 72 characters (see this blog post for why).

If the change affects more than one subsystem, you can use comma to separate them like util/codec,util/types:.

If the change affects many subsystems, you can use * instead, like *:.

The body of the commit message should describe why the change was made and at a high level, how the code works.

Signing off the Commit

The project uses DCO check and the commit message must contain a Signed-off-by line for Developer Certificate of Origin.

Use option git commit -s to sign off your commits.