---
title: "otelcol.receiver.prometheus | Grafana Cloud documentation"
description: "Learn about otelcol.receiver.prometheus"
---

# `otelcol.receiver.prometheus`

`otelcol.receiver.prometheus` receives Prometheus metrics, converts them to the OpenTelemetry metrics format, and forwards them to other `otelcol.*` components. This is a custom component built on a fork of the upstream OpenTelemetry Collector receiver.

You can specify multiple `otelcol.receiver.prometheus` components by giving them different labels.

> Note
> 
> Support for translating Prometheus native histograms into OTLP exponential histograms is a public preview feature. To enable native histogram translation, run Alloy with the `--stability.level=public-preview` configuration flag.

> Note
> 
> In Alloy v1.14.0, `otelcol.receiver.prometheus` no longer sets OTLP metric [start times](https://github.com/open-telemetry/opentelemetry-proto/blob/v1.9.0/opentelemetry/proto/metrics/v1/metrics.proto#L181-L187) for Prometheus metrics. The receiver forwards metrics without adding start times when the Prometheus input doesn’t have a [created time](https://github.com/prometheus/OpenMetrics/blob/v1.0.0/specification/OpenMetrics.md#suffixes).
> 
> Start time indicates when a cumulative metric such as an OTLP “sum” or a Prometheus “counter” was last reset. If your database uses start times for OTLP metrics, you can use `otelcol.processor.metric_start_time` to set it. The OTLP endpoint for Grafana Mimir and the OTLP Gateway for Grafana Cloud both support OTLP metric start time.
> 
> To add the start time in the same way that `otelcol.receiver.prometheus` did prior to Alloy v1.14.0, configure `otelcol.processor.metric_start_time` with `strategy` set to `true_reset_point`.
> 
> It’s only necessary to use `true_reset_point` if your Mimir or Grafana Cloud instance is explicitly configured with a `-distributor.otel-created-timestamp-zero-ingestion-enabled=true` flag, since `true_reset_point` sends a sample with the same start and end time, and Mimir by default doesn’t create a zero sample for it. For most Mimir and Grafana Cloud use cases, there’s no change in behavior even if you don’t add `otelcol.processor.metric_start_time`.

## Usage

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
otelcol.receiver.prometheus "<LABEL>" {
  output {
    metrics = [...]
  }
}
```

## Arguments

The `otelcol.receiver.prometheus` component doesn’t support any arguments. You can configure this component with blocks.

## Blocks

You can use the following blocks with `otelcol.receiver.prometheus`:

No valid configuration blocks found.

### `output`

Required

The `output` block configures a set of components to forward resulting telemetry data to.

The following arguments are supported:

Expand table

| Name      | Type                     | Description                           | Default | Required |
|-----------|--------------------------|---------------------------------------|---------|----------|
| `logs`    | `list(otelcol.Consumer)` | List of consumers to send logs to.    | `[]`    | no       |
| `metrics` | `list(otelcol.Consumer)` | List of consumers to send metrics to. | `[]`    | no       |
| `traces`  | `list(otelcol.Consumer)` | List of consumers to send traces to.  | `[]`    | no       |

You must specify the `output` block, but all its arguments are optional. By default, telemetry data is dropped. Configure the `metrics`, `logs`, and `traces` arguments accordingly to send telemetry data to other components.

### `debug_metrics`

The `debug_metrics` block configures the metrics that this component generates to monitor its state.

The following arguments are supported:

Expand table

| Name                               | Type      | Description                                          | Default | Required |
|------------------------------------|-----------|------------------------------------------------------|---------|----------|
| `disable_high_cardinality_metrics` | `boolean` | Whether to disable certain high cardinality metrics. | `true`  | no       |

`disable_high_cardinality_metrics` is the Alloy equivalent to the `telemetry.disableHighCardinalityMetrics` feature gate in the OpenTelemetry Collector. It removes attributes that could cause high cardinality metrics. For example, attributes with IP addresses and port numbers in metrics about HTTP and gRPC connections are removed.

> Note
> 
> If configured, `disable_high_cardinality_metrics` only applies to `otelcol.exporter.*` and `otelcol.receiver.*` components.

## Exported fields

This component exports the following fields that other components can reference:

Expand table

| Name       | Type              | Description                                                          |
|------------|-------------------|----------------------------------------------------------------------|
| `receiver` | `MetricsReceiver` | A value that other components can use to send Prometheus metrics to. |

## Component health

`otelcol.receiver.prometheus` is only reported as unhealthy if given an invalid configuration.

## Debug information

`otelcol.receiver.prometheus` doesn’t expose any component-specific debug information.

## Example

This example uses the `otelcol.receiver.prometheus` component as a bridge between the Prometheus and OpenTelemetry ecosystems. The component exposes a receiver which the `prometheus.scrape` component uses to send Prometheus metric data to. The receiver converts the metrics to OTLP format and forwards them to the `otelcol.exporter.otlphttp` component, which sends them to an OTLP-capable endpoint:

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
prometheus.scrape "default" {
    // Collect metrics from the default HTTP listen address.
    targets = [{"__address__"   = "127.0.0.1:12345"}]

    forward_to = [otelcol.receiver.prometheus.default.receiver]
}

otelcol.receiver.prometheus "default" {
  output {
    metrics = [otelcol.exporter.otlphttp.default.input]
  }
}

otelcol.exporter.otlphttp "default" {
  client {
    endpoint = sys.env("OTLP_ENDPOINT")
  }
}
```

## Compatible components

`otelcol.receiver.prometheus` can accept arguments from the following components:

- Components that export [OpenTelemetry `otelcol.Consumer`](/docs/grafana-cloud/send-data/alloy/reference/compatibility/#opentelemetry-otelcolconsumer-exporters)

`otelcol.receiver.prometheus` has exports that can be consumed by the following components:

- Components that consume [Prometheus `MetricsReceiver`](/docs/grafana-cloud/send-data/alloy/reference/compatibility/#prometheus-metricsreceiver-consumers)

> Note
> 
> Connecting some components may not be sensible or components may require further configuration to make the connection work correctly. Refer to the linked documentation for more details.