# Technical Documentation: prometheus/client_golang

> ℹ️ **Provenance:** Multi-Tier Ingestion · [CodeWiki Reference](https://codewiki.google/github.com/prometheus/client_golang)

### Overview (`README.md`)

# Prometheus Go client library

[](https://pkg.go.dev/github.com/prometheus/client_golang)
[](https://securityscorecards.dev/viewer/?uri=github.com/prometheus/client_golang)
[](https://slack.cncf.io/)

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.

## Version Compatibility

This library supports the two most recent major releases of Go. While it may function with older versions, we only provide fixes and support for the currently supported Go releases.

> [!NOTE]
> See our [Release Process](RELEASE.md#supported-go-versions) for details on compatibility and support policies.

## 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), but plans for further development of v2 at the moment.

> NOTE: The initial v2 attempt is in a [separate branch](https://github.com/prometheus/client_golang/tree/dev-v2). We also started
experimenting on a new `prometheus.V2.*` APIs in [the 1.x's V2 struct](https://github.com/prometheus/client_golang/blob/main/prometheus/vnext.go#L23). Help wanted!

## Instrumenting applications

[](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.

## Pushing metrics via OpenTelemetry OTLP

Applications instrumented with `client_golang` can also export their
metrics via the OpenTelemetry OTLP push protocol without re-instrumenting
against a different metric API. The
[`go.opentelemetry.io/contrib/bridges/prometheus`](https://pkg.go.dev/go.opentelemetry.io/contrib/bridges/prometheus)
module wraps a `prometheus.Registry` as an OpenTelemetry metric producer,
which an OTLP exporter (HTTP or gRPC) can then push to an OTel collector
or OTLP-accepting backend. This is useful for batch jobs or environments
where pull-based `/metrics` scraping is not an option.

Pull-based collection via `promhttp` remains the recommended default for
reliability, central discovery, and failover. The bridge is intended as
an additional option, not a replacement.

See the [bridge's Go reference](https://pkg.go.dev/go.opentelemetry.io/contrib/bridges/prometheus)
and [source](https://github.com/open-telemetry/opentelemetry-go-contrib/tree/main/bridges/prometheus)
for setup details.

## Client for the Prometheus HTTP API

[](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.

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

---

### Overview (`exp/README.md`)

# client_golang experimental module

Contains experimental utilities and APIs for Prometheus.

Packages within this module are listed below.

## Remote

This module contains production quality code with explicitly unstable API. Any code in this module can change its API or be removed; use with care.

The intention is that, with maturity some of the packages would graduate to stable version of client_golang module.

Packages within this module are listed below.

## Remote

NOTE: The `api/remote` package is used by `prometheus/prometheus`. Any changes to this package should ensure Prometheus is not affected (e.g. does not break Prometheus on upgrade or if it breaks, the Prometheus gets updated soon.
Implements bindings from Prometheus remote APIs (remote write v1 and v2 for now).

Contains flexible method for building API clients, that can send remote write protocol messages.

```go
    import (
        "github.com/prometheus/client_golang/exp/api/remote"
    )
    ...

	remoteAPI, err := remote.NewAPI(
		"https://your-remote-endpoint",
		remote.WithAPIHTTPClient(httpClient),
		remote.WithAPILogger(logger.With("component", "remote_write_api")),
	)
    ...

    stats, err := remoteAPI.Write(ctx, remote.WriteV2MessageType, protoWriteReq)
```

Also contains handler methods for applications that would like to handle and store remote write requests.

```go
    import (
        "net/http"
        "log"

        "github.com/prometheus/client_golang/exp/api/remote"
    )
    ...
    
    type db {}

    func NewStorage() *db {}

    func (d *db) Store(ctx context.Context, msgType remote.WriteMessageType, req *http.Request) (*remote.WriteResponse, error) {}
    ...

	mux := http.NewServeMux()

	remoteWriteHandler := remote.NewHandler(storage, remote.WithHandlerLogger(logger.With("component", "remote_write_handler")))
	mux.Handle("/api/v1/write", remoteWriteHandler)

	server := &http.Server{
		Addr:    ":8080",
		Handler: mux,
	}
	if err := server.ListenAndServe(); err != nil {
		log.Fatal(err)
	}
```

For more details, see [go doc](https://pkg.go.dev/github.com/prometheus/client_golang/exp/api/remote).

---

### Overview (`prometheus/README.md`)

See [](https://pkg.go.dev/github.com/prometheus/client_golang/prometheus).

---

### Overview (`tutorials/whatsup/README.md`)

# client_golang Tutorial: "WhatsUp"

See [slides](./ContribFest.pdf)

---

### Overview (`internal/github.com/golang/gddo/README.md`)

This source code is a stripped down version from the archived repository https://github.com/golang/gddo and licensed under BSD.

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