Contributing

Prometheus uses GitHub to manage reviews of pull requests.

If you are a new contributor see: Steps to Contribute
If you have a trivial fix or improvement, go ahead and create a pull request, addressing (with @...) a suitable maintainer of this repository (see MAINTAINERS.md) in the description of the pull request.
If you plan to do something more involved, first discuss your ideas on our mailing list. This will avoid unnecessary work and surely give you and us a good deal of inspiration. Also please see our non-goals issue on areas that the Prometheus community doesn't plan to work on.
Relevant coding style guidelines are the Go Code Review Comments and the Formatting and style section of Peter Bourgon's Go: Best Practices for Production Environments.
Be sure to sign off on the DCO.

Steps to Contribute

Should you wish to work on an issue, please claim it first by commenting on the GitHub issue that you want to work on it. This is to prevent duplicated efforts from contributors on the same issue.

Please check the low-hanging-fruit label to find issues that are good for getting started. If you have questions about one of the issues, with or without the tag, please comment on them and one of the maintainers will clarify it. For a quicker response, contact us over IRC.

You can spin up a prebuilt dev environment using Gitpod.io.

For complete instructions on how to compile see: Building From Source

For quickly compiling and testing your changes do:

# For building.
go build ./cmd/prometheus/
./prometheus

# For testing.
make test         # Make sure all the tests pass before you commit and push :)

To run a collection of Go linters through golangci-lint, do:

make lint

If it reports an issue and you think that the warning needs to be disregarded or is a false-positive, you can add a special comment //nolint:linter1[,linter2,...] before the offending line. Use this sparingly though, fixing the code to comply with the linter's recommendation is in general the preferred course of action. See this section of the golangci-lint documentation for more information.

All our issues are regularly tagged so that you can also filter down the issues involving the components you want to work on. For our labeling policy refer the wiki page.

Pull Request Checklist

Branch from the main branch and, if needed, rebase to the current main branch before submitting your pull request. If it doesn't merge cleanly with main you may be asked to rebase your changes.
Commits should be as small as possible, while ensuring that each commit is correct independently (i.e., each commit should compile and pass tests).
If your patch is not getting reviewed or you need a specific person to review it, you can @-reply a reviewer asking for a review in the pull request or a comment, or you can ask for a review on the IRC channel #prometheus-dev on irc.libera.chat (for the easiest start, join via Element).
Add tests relevant to the fixed bug or new feature.

Dependency management

The Prometheus project uses Go modules to manage dependencies on external packages.

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

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

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

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

# The GO111MODULE variable can be omitted when the code isn't located in GOPATH.
GO111MODULE=on go mod tidy

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

Working with the PromQL parser

The PromQL parser grammar is located in promql/parser/generated_parser.y and it can be built using make parser. The parser is built using goyacc

If doing some sort of debugging, then it is possible to add some verbose output. After generating the parser, then you can modify the ./promql/parser/generated_parser.y.go manually.

// As of writing this was somewhere around line 600.
var (
	yyDebug        = 0 // This can be a number 0 -> 5.
	yyErrorVerbose = false  // This can be set to true.
)

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