CONTRIBUTING.md

Contributing

This document explains the process of contributing to the Thanos project.

First of all please follow the CODE_OF_CONDUCT in all your interactions within the project.

Thanos Philosophy

The philosophy of Thanos and our community borrows heavily from UNIX philosophy and the Golang programming language.

• Each subcommand should do one thing and do it well.
  • eg. Thanos query proxies incoming calls to known store API endpoints merging the result
• Write components that work together.
  • e.g. blocks should be stored in native Prometheus format
• Make it easy to read, write, and run components.
  • e.g. reduce complexity in system design and implementation

Feedback / Issues

If you encounter any issue or you have an idea to improve, please:

• Search through Google and existing open and closed GitHub Issues for the answer first. If you find a relevant topic, please comment on the issue.
• If none of the issues are relevant, please add an issue to GitHub issues. Please provide any relevant information as suggested by the Issue template.
• If you have a quick question you might want to also ask on #thanos or #thanos-dev slack channel in the CNCF workspace. We recommend using GitHub issues for issues and feedback, because GitHub issues are trackable.

If you encounter a security vulnerability, please refer to Reporting a Vulnerability process

Adding New Features / Components

When contributing a complex change to Thanos repository, please discuss the change you wish to make within a Github issue, in Slack, or by another method with the owners of this repository before making the change.

Adding a large new feature or/and component to Thanos should be done by first creating a proposal document outlining the design decisions of the change, motivations for the change, and any alternatives that might have been considered.

General Naming

In the code and documentation prefer non-offensive terminology, for example:

• allowlist / denylist (instead of whitelist / blacklist)
• primary / replica (instead of master / slave)
• openbox / closedbox (instead of whitebox / blackbox)

Components Naming

Thanos is a distributed system comprised of several services and CLI tools as listed here.

When we refer to them in a technical capacity we use the verbal form: store, compact, rule, query, query-frontend. This includes:

• Code
• Metrics
• Commands
• Mixin examples: alerts, rules, dashboards
• Container names
• Flags and configuration
• Package names
• Log messages, traces

However, when discussing these components in a more general manner we use the actor noun form: store gateway, compactor, ruler, querier, query frontend. This includes areas like:

• Public communication
• Documentation
• Code comments

Development

The following section explains various suggestions and procedures to note during development of Thanos.

Prerequisites

• It is strongly recommended that you use Linux distributions systems or macOS for development.
• Running WSL 2 (on Windows) is also possible. Note that if during development you run a local Kubernetes cluster and have a Service with service.spec.sessionAffinity: ClientIP, it will break things until it's removed¹.
• Go 1.21.x or higher.
• Docker (to run e2e tests)
• For React UI, you will need a working NodeJS environment and the npm package manager to compile the Web UI assets.

First Steps

It's key to get familiarized with the style guide and mechanics of Thanos, especially if your contribution touches more than one component of the Thanos distributed system. We recommend:

• Reading the getting started docs and working through them, or alternatively working through the Thanos tutorial.
• Familiarizing yourself with our coding style guidelines..
• Familiarizing yourself with the Makefile commands, for example format, build, proto, docker and test. make help will print most of available commands with relevant details.
• To get started, create a codespace for this repository by clicking this 👉
  • A codespace will open in a web-based version of Visual Studio Code. The dev container is fully configured with software needed for this project.
  • Note: Dev containers is an open spec which is supported by GitHub Codespaces and other tools.
• In case you want to develop the project locally, install Golang in your machine. Here is a nice gist for this purpose.
• You can run an interactive example, which populates some data as well, by following the steps mentioned here.

Installing Project locally in your machine

• Find any directory in your system your want Thanos repo in. e.g ~/Repos -

  • cd ~/Repos

  • Make sure that the GOBIN, GOPATH and GOPROXY (useful) environment variables are set and that GOBIN is included in your PATH. You may use GOPROXY=https://goproxy.cn as an alternative if you cannot visit https://proxy.golang.org. For example -

    export GOBIN="~/Repos/thanos/.bin" # It's nice to have local tooling installed and stored locally.
    
    export GOPATH="~/Repos/thanosgopath" # Use if you want to have an isolated directory for deps, otherwise, the directory where you have installed golang will be used.
    
    export GOPROXY="https://proxy.golang.org"
    export PATH="$GOBIN:$PATH"
    

  • Consider adding the environment variables to your host machine (e.g /.bashrc or .envrc) file so that those environment variables are persisted across sessions.

• Clone Thanos inside the ~/Repos folder -
  • For HTTPS - git clone https://github.com/thanos-io/thanos.git
  • For SSH - git clone git@github.com:thanos-io/thanos.git
• Once installed, you can run make help inside Thanos folder for getting a list of helper commands which are provided for making development easy for you :)

Building/Running/Developing

• Run make help for getting a list of helper commands that will make your development life much more easy. Especially consider using make lint often. It provides auto linting and formatter for making sure the code quality meets the standards of contribution.
• Usually, while sending in a PR make build, make format, make lint, make test, make docs, make check-docs, make quickstart are the most used commands while developing Thanos.
• When you run make build from Thanos repo root, code is compiled and a binary named thanos is created and built into your $GOBIN or $GOPATH/bin.
• In case you are working on a component of Thanos, you would love it if you don’t have to set up the yaml configuration for Prometheus and other components, before you start running the component. This is a repetitive task, and the Thanos Community has provided commands/script for automating the running of components -
  • Run make quickstart for spinning up all components of Thanos quickly.
  • If you want to run specific components instead of all, feel free to use and edit - quickstart.sh

Pull Request Process

Forking and Creating the local setup for developing Thanos

Start your development with forking thanos-io/thanos.git . Here are sample steps to setup your development environment:

$ GOPATH=$(go env GOPATH)
$ mkdir -p $GOPATH/src/github.com/thanos-io
$ cd $GOPATH/src/github.com/thanos-io
$ git clone https://github.com/<your_github_id>/thanos.git
$ cd thanos
$ git remote add upstream https://github.com/thanos-io/thanos.git
$ git remote update
$ git merge upstream/main
$ make build
$ export PATH=$PATH:$GOPATH/bin
$ thanos -h

Signing your work: DCO (Developer Certificate of Origin) Process.

• By contributing to this project you agree to the Developer Certificate of Origin(DCO). This document was created by the Linux Kernel community and is a simple statement that you, as a contributor, have the legal right to make the contribution.
• To signoff, you need to add Signed-off-by: Your Name <your email id> at the end of your commit messages. You can do this using git commit -s. For example:

$ git commit -s -m 'This is my commit message'

• You can also alias commit as commit -s in your ~/.gitconfig to signoff all your future commits.
• If you have authored an unsigned commit, you can update it using git commit --amend --signoff. If you've pushed your changes to GitHub already you'll need to force push your branch after this with git push -f.

1. Keep PRs as small as possible. For each of your PRs, you create a new branch based on the latest main. Chain them if needed (base one PR on other PRs). You can read more details about the workflow from here.

$ git checkout main
$ git remote update
$ git merge upstream/main
$ git checkout -b <your_branch_for_new_pr>
$ make build
$ <Iterate your development>
$ git push origin <your_branch_for_new_pr>

Tests your changes

Formatting

First of all, fall back to make help to see all availible commands. There are a few checks that happen when making a PR and these need to pass. We can make sure locally before making the PR by using commands that are related to your changes:

• make docs generates, formats and cleans up white noise.
• make changed-docs does same as above, but just for changed docs by checking git diff on which files are changed.
• make check-docs generates, formats, cleans up white noise and checks links. Since it can be annoying to wait on link check results - it takes forever - to skip the check, you can use make docs).
• make format formats code

If you only made documentation changes, which do not include a link, you will be fine by using make docs. If you also changed some code, run make format as well.

Updating your branch

It is a good practice to keep your branch updated by rebasing your branch to main.

• Update your main - git checkout main; git pull <remote_name> main
• Rebase your main - git rebase -i main

Changelog and Review Procedure

• If your change affects users (adds or removes feature) consider adding the item to the CHANGELOG.
• You may merge the Pull Request once you have the sign-off of at least one developer with write access, or if you do not have permission to do that, you may request the second reviewer to merge it for you.
• If you feel like your PR is waiting too long for a review, feel free to ping the #thanos-dev channel on our slack for a review!
• If you are a new contributor with no write access, you can tag in the respective maintainer for the changes, but be patient enough for the reviews. Remember, good things take time :)

Dependency management

The Thanos project uses Go modules to manage dependencies on external packages. This requires a working Go environment with version 1.11 or greater and git installed.

To add or update a new dependency, use the go get command:

# Pick the latest tagged release.
go get example.com/some/module/pkg

# Pick a specific version.
go get example.com/some/module/pkg@vX.Y.Z

Tidy up the go.mod and go.sum files:

make deps
git add go.mod go.sum
git commit

You have to commit the changes to go.mod and go.sum before submitting the pull request.

Running Tests

• Thanos provides make commands that help you run the tests locally.
• If you don't have a live object store ready, you can use the make test-local command.
• NOTE: This command skips tests against live object storage systems by specifying environment variables; this causes the store-specific tests to be run against memory and filesystem object storage types only. The CI tests run uses GCS, AWS and Swift.
• Not specifying these variables will result in auth errors against GCS, AWS, Azure, COS etc.
• If you have a decent hardware to run the tests, you can run them locally.
• If you want to run the tests once in a while, it is suitable for you to send in a PR, the built in CI/CD setup runs the tests for you, which is nice for once in a while run.
• make test: Runs all Thanos Go unit tests against each supported version of Prometheus. This excludes tests in ./test/e2e.
• make test-local: Runs test excluding tests for ALL object storage integrations.
• make test-e2e: Runs all Thanos e2e docker-based e2e tests from test/e2e. Required access to docker daemon.
• make test-e2e-local: Runs all thanos e2e tests locally.

Advanced testing

At some point during development it is useful, in addition to running unit or e2e tests, to run and play with Thanos components manually. While you can run any component manually by crafting specific flags for a test setup, there are already some nice tools and scripts available. Consider the following methods:

• make quickstart: this command spins up a simple setup of all Thanos components.
• make test-e2e: the e2e tests cover most of the setups and functionality Thanos offers. It's extremely easy to add time.Sleep(10* time.Minute) at certain points in the tests (e.g for compactor here). This way when you run make test-e2e, the test will sleep for some time, allowing you to connect to the setup manually using the port printed in the logs. For example:

querier-1: level=info name=querier-1 ts=2020-04-01T12:53:56.101029491Z caller=http.go:56 service=http/server component=query msg="listening for requests and metrics" address=:80
querier-1: level=info name=querier-1 ts=2020-04-01T12:53:56.101106805Z caller=intrumentation.go:48 msg="changing probe status" status=ready
querier-1: level=info name=querier-1 ts=2020-04-01T12:53:56.101290229Z caller=grpc.go:106 service=gRPC/server component=query msg="listening for StoreAPI gRPC" address=:9091
Ports for container: e2e_test_store_gateway-querier-1 Mapping: map[80:32825 9091:32824]

This output indicates that the HTTP (80) endpoint will be available on http://localhost:32825. You can quickly craft your own test case with our framework as well!

NOTE: make docker has to work in order for make test-e2e to run. This currently might not work properly on macOS.

Footnotes

1. A WSL 2 kernel recompilation is required to enable the xt_recent kernel module, used by iptables in kube-proxy to implement ClientIP session affinity. See issue in WSL. ↩