Documentation Grafana Alloy Reference Components prometheus prometheus.echo

prometheus.echo

The prometheus.echo component receives Prometheus metrics and writes them to stdout in Prometheus exposition format. This component is useful for debugging and testing the flow of metrics through a pipeline, allowing you to see exactly what metrics are being received at a particular point in your configuration.

Usage

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prometheus.echo "<LABEL>" {
}

Arguments

You can use the following arguments with prometheus.echo:

The format argument controls how metrics are encoded when written to stdout:

• text - Uses the Prometheus text exposition format (default).
• openmetrics - Uses the OpenMetrics text format.

Blocks

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

Exported fields

The following fields are exported and can be referenced by other components:

Component health

prometheus.echo is only reported as unhealthy if given an invalid configuration. In those cases, exported fields retain their last healthy values.

Debug information

prometheus.echo doesn’t expose any component-specific debug information.

Debug metrics

prometheus.echo doesn’t expose any component-specific debug metrics.

Example

This example creates a metrics generation and inspection pipeline:

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prometheus.exporter.unix "default" {
}

prometheus.scrape "demo" {
  targets    = prometheus.exporter.unix.default.targets
  forward_to = [prometheus.echo.debug.receiver]
}

prometheus.echo "debug" {
  format = "text"
}

In this example:

1. The prometheus.exporter.unix component exposes system metrics.
2. The prometheus.scrape component scrapes those metrics.
3. The prometheus.echo component receives the scraped metrics and writes them to stdout in Prometheus text format.

When you run this configuration, you’ll see the metrics being written to stdout, which is useful to:

• Debug metric collection issues
• Verify metric labels and values
• Test metric transformations
• Understand the structure of metrics in your pipeline

Example with OpenMetrics format

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prometheus.scrape "demo" {
  targets = [
    {"__address__" = "localhost:9090"},
  ]
  forward_to = [prometheus.echo.debug.receiver]
}

prometheus.echo "debug" {
  format = "openmetrics"
}

This example outputs metrics using the OpenMetrics format instead of the traditional Prometheus text format.

Compatible components

prometheus.echo has exports that can be consumed by the following components:

• Components that consume Prometheus MetricsReceiver