# Prometheus Go client library

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This is the [Go](http://golang.org) client library for
[Prometheus](http://prometheus.io). It has two separate parts, one for
instrumenting application code, and one for creating clients that talk to the
Prometheus HTTP API.

__This library requires Go1.17 or later.__

## Important note about releases and stability

This repository generally follows [Semantic
Versioning](https://semver.org/). However, the API client in
prometheus/client_golang/api/… is still considered experimental. Breaking
changes of the API client will _not_ trigger a new major release. The same is
true for selected other new features explicitly marked as **EXPERIMENTAL** in
CHANGELOG.md.

Features that require breaking changes in the stable parts of the repository
are being batched up and tracked in the [v2
milestone](https://github.com/prometheus/client_golang/milestone/2). The v2
development happens in a [separate
branch](https://github.com/prometheus/client_golang/tree/dev-v2) for the time
being. v2 releases off that branch will happen once sufficient stability is
reached. In view of the widespread use of this repository, v1 and v2 will
coexist for a while to enable a convenient transition.

## Instrumenting applications

[![code-coverage](http://gocover.io/_badge/github.com/prometheus/client_golang/prometheus)](http://gocover.io/github.com/prometheus/client_golang/prometheus) [![Go Reference](https://pkg.go.dev/badge/github.com/prometheus/client_golang/prometheus.svg)](https://pkg.go.dev/github.com/prometheus/client_golang/prometheus)

The
[`prometheus` directory](https://github.com/prometheus/client_golang/tree/main/prometheus)
contains the instrumentation library. See the
[guide](https://prometheus.io/docs/guides/go-application/) on the Prometheus
website to learn more about instrumenting applications.

The
[`examples` directory](https://github.com/prometheus/client_golang/tree/main/examples)
contains simple examples of instrumented code.

## Client for the Prometheus HTTP API

[![code-coverage](http://gocover.io/_badge/github.com/prometheus/client_golang/api/prometheus/v1)](http://gocover.io/github.com/prometheus/client_golang/api/prometheus/v1) [![Go Reference](https://pkg.go.dev/badge/github.com/prometheus/client_golang/api.svg)](https://pkg.go.dev/github.com/prometheus/client_golang/api)

The
[`api/prometheus` directory](https://github.com/prometheus/client_golang/tree/main/api/prometheus)
contains the client for the
[Prometheus HTTP API](http://prometheus.io/docs/querying/api/). It allows you
to write Go applications that query time series data from a Prometheus
server. It is still in alpha stage.

## Where is `model`, `extraction`, and `text`?

The `model` packages has been moved to
[`prometheus/common/model`](https://github.com/prometheus/common/tree/main/model).

The `extraction` and `text` packages are now contained in
[`prometheus/common/expfmt`](https://github.com/prometheus/common/tree/main/expfmt).

## Contributing and community

See the [contributing guidelines](CONTRIBUTING.md) and the
[Community section](http://prometheus.io/community/) of the homepage.

`clint_golang` community is also present on the CNCF Slack `#prometheus-client_golang`.

### For Maintainers: Release Process

To cut minor version:

1. Create new branch `release-<major>.<minor>` on top of main commit you want to cut version from and push it.
2. Create new branch on top of release branch.
3. Change `VERSION` file.
4. Update `CHANGELOG` (only user-impacting changes to mention).
5. Create PR, get it reviewed.
6. Once merged, create release for `release-<major>.<minor>` tag on GitHub with `<version> / <date>` title.
7. Announce on prometheus-announce mailing list, slack and Twitter.
8. Merge release branch back to main using "merge without squashing" approach (!).

To cut patch version:

1. Create branch on top of release branch you want to use. 
2. Cherry-pick fixes from main or add commits to fix critical bugs only for that patch release.
3. Follow steps 3-8 as above.