Faro Receiver - Propagate certain headers to measurements

Request

I'd like to be able to grab certain headers from the incoming Faro payload and insert them into the logfmt key-value pairs generated when Faro creates a log line for measurements.

Maybe this could include log, event, and exception types too, but I don't see that as being particularly useful.

Use case

I'd like to include certain viewer request headers on measurements, like latitude and longitude. By including this metadata on measurements, we could graph page load times by geographic region using Grafana's geomap panel.

We can enable include_metadata in the Faro receiver, but that only propagates connection metadata to the downstream otelcol.Consumer for traces. Example of adding latitude and longitude to traces:

faro.receiver "faro" {
  server {
    include_metadata = true
    // other receiver config
  }

  output {
    logs   = [ /* ... */ ]
    traces = [otelcol.processor.attributes.headers.input]
  }
}

otelcol.processor.attributes "headers" {
  action {
    key = "http.client.latitude"
    from_context = "metadata.cloudfront-viewer-latitude"
    action = "upsert"
  }

  action {
    key = "http.client.longitude"
    from_context = "metadata.cloudfront-viewer-longitude"
    action = "upsert"
  }

  output {
    traces = [otelcol.exporter.otlphttp.traces.input]
  }
}

otelcol.exporter.otlphttp "traces" {
  client {
    endpoint = "https://tempo:443"
  }
}

One idea for measurements would be an optional config block in faro.receiver that could map headers to logfmt fields:

faro.receiver "faro" {
  server {
    include_metadata = true
    // other receiver config
  }

  headers {
    mapping = {
      latitude = "cloudfront-viewer-latitude",
      longitude = "cloudfront-viewer-longitude",
    }
  }

  output {
    logs   = [loki.process.faro.receiver]
  }
}

loki.process "faro" {
  stage.logfmt {
    mapping = {
      latitude = "",
      longitude = "",
    }
  }

  stage.structured_metadata {
    values = {
      latitude = "",
      longitude = "",
    }
  }

  forward_to = [loki.write.logs.receiver]
}

loki.write "logs" {
  endpoint {
    url = "https://loki:443"
  }
}

grafana / alloy

Faro Receiver - Propagate certain headers to measurements #1538

Request

Use case