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OTLP Metrics

The OTLP Metrics Function transforms dimensional metrics events into the OTLP (OpenTelemetry Protocol) format. This Function can be used to send metric events (events that contain the internal field __criblMetrics) to any OpenTelemetry Metrics-capable destinations.

For detailed insights into events that passed through the Function but were dropped, set the logging level for channel func:otlp_metrics to debug, and there will be a stats log message output once per minute with the relevant information.

This Function will delete the internal attribute __criblMetrics, making events only suitable for destinations that use the OTLP format.

Usage
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Filter: Filter expression (JS) that selects data to feed through the Function. The default true setting passes all events through the Function.

Description: Simple description of this Function’s purpose in this Pipeline. Defaults to empty.

Final: If toggled to Yes, stops feeding data to the downstream Functions. Defaults to No.

Resource attribute prefixes: The prefixes of top-level attributes to add as resource attributes. Each attribute must match the regex pattern ^[a-zA-Z0-9]+$. Use Eval to copy nested attributes to the top level for matching. See the OpenTelemetry documentation for Resource Semantic Conventions. Remove all the prefixes if you want to bring none of the Resources over.

Drop non-metric events: Whether or not to drop any non-metric events.

Basic Example
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Filter: __inputId=='prometheus_rw:prom_rw_in'

This will grab all events from a Prometheus Remote Write Source and convert the metrics to OTLP format.

Ensure that the internal attribute __criblMetrics does not contain null or blank values in any of the child object arrays.

Sample event:

{
  "__criblEventType": "event",
  "__ctrlFields": [],
  "__final": false,
  "__cloneCount": 0,
  "_time": 1700236380.37,
  "_value": 123.456,
  "_metric": "cribl_logstream_health_outputs",
  "_metric_type": "gauge",
  "cribl_host": "P4MD6R-Pv8x",
  "cribl_wp": "w0",
  "event_host": "P4MD6R-Pv8x",
  "event_source": "cribl",
  "host": "P4MD6R-Pv8x",
  "output": "open_telemetry:otel_webhook_dest",
  "source": "cribl",
  "__criblMetrics": [
    {
      "nameExpr": ["_metric"],
      "values": ["_value"],
      "types": ["gauge"],
      "dims": [
        "cribl_host",
        "cribl_wp",
        "event_host",
        "event_source",
        "host",
        "output",
        "source"
      ]
    }
  ],
  "__offset": 8099,
  "__bytes": 228,
  "__srcIpPort": "127.0.0.1:50868",
  "__inputId": "prometheus_rw:prom_rw_in",
  "service.name": "serviceName",
  "service.instanceId": "serviceInstanceId",
  "system": "system",
  "system.name": "systemName",
  "telemetry.sdk.name": "opentelemetry",
  "telemetry.sdk.language": "java",
  "k8s.cluster.name": "opentelemetry-cluster",
  "cloud.account.id": 1111111,
  "cloud.platform": "aws"
}

The same sample event after conversion by the OTLP Metrics Function:

{
  "_time": 1700236380.37,
  "resource": {
    "attributes": [
      {
        "key": "env",
        "value": { "string_value": "prod" }
      },
      {
        "key": "hostname",
        "value": { "string_value": "myhost" }
      },
      {
        "key": "datacenter",
        "value": { "string_value": "sdc" }
      },
      {
        "key": "region",
        "value": { "string_value": "europe" }
      },
      {
        "key": "owner",
        "value": { "string_value": "frontend" }
      },
      {
        "key": "host",
        "value": { "string_value": "6V2GQ1-Ehi1" }
      },
      {
        "key": "source",
        "value": { "string_value": "http://localhost:9100/metrics" }
      },
      {
        "key": "service.name",
        "value": { "string_value": "serviceName" }
      },
      {
        "key": "service.instanceId",
        "value": { "string_value": "serviceInstanceId" }
      },
      {
        "key": "system.name",
        "value": { "string_value": "systemName" }
      },
      {
        "key": "telemetry.sdk.name",
        "value": { "string_value": "opentelemetry" }
      },
      {
        "key": "telemetry.sdk.language",
        "value": { "string_value": "java" }
      },
      {
        "key": "k8s.cluster.name",
        "value": { "string_value": "opentelemetry-cluster" }
      },
      {
        "key": "cloud.account.id",
        "value": { "int_value": 1111111 }
      },
      {
        "key": "cloud.platform",
        "value": { "string_value": "aws" }
      }
    ]
  },
  "instrumentation_library_metrics": [
    {
      "schema_url": "",
      "metrics": [
        {
          "name": "cribl_logstream_health_outputs",
          "gauge": {
            "data_points": [
              {
                "as_double": 123.456,
                "time_unix_nano": 1700236380370000000,
                "start_time_unix_nano": 1700236380370000000,
                "attributes": [
                  {
                    "key": "cribl_host",
                    "value": { "string_value": "P4MD6R-Pv8x" }
                  },
                  {
                    "key": "cribl_wp",
                    "value": { "string_value": "w0" }
                  },
                  {
                    "key": "event_host",
                    "value": { "string_value": "P4MD6R-Pv8x" }
                  },
                  {
                    "key": "event_source",
                    "value": { "string_value": "cribl" }
                  },
                  {
                    "key": "host",
                    "value": { "string_value": "P4MD6R-Pv8x" }
                  },
                  {
                    "key": "output",
                    "value": {
                      "string_value": "open_telemetry:otel_webhook_dest"
                    }
                  },
                  {
                    "key": "source",
                    "value": { "string_value": "cribl" }
                  }
                ]
              }
            ]
          },
          "__type": "gauge"
        }
      ]
    }
  ]
}