Cribl Stream OpenTelemetry Source Rejects AWS ADOT Lambda Exponential Histogram Metrics

Symptom

When the AWS ADOT Lambda distro exports histogram metrics, its default aggregation can produce ExponentialHistogram payloads. Cribl Stream logs got an unsupported metric type; these metrics are rejected and do not reach downstream Destinations.

Environment

• Cribl Stream OpenTelemetry Source receiving OTLP metrics.
• AWS ADOT Lambda distro exporting histogram metrics.
• Histogram aggregation set to ExponentialHistogram by the sender default.

Resolution

1. Review the OpenTelemetry Source logs for got an unsupported metric type and record the affected metric names.
2. Verify that the affected metrics originate from an AWS ADOT Lambda distro.
3. Configure the Lambda function to use explicit-bucket histogram aggregation instead of ExponentialHistogram aggregation.
4. Set the OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION environment variable to this value:
   explicit_bucket_histogram
5. Redeploy or restart the upstream sender.
6. Verify that the OpenTelemetry Source no longer logs the unsupported metric error.
7. Verify that the histogram metrics reach the configured downstream Destination.

Cause

This can be caused by:

• The AWS ADOT Lambda distro defaults histogram instruments to the ExponentialHistogram metric type.
• ExponentialHistogram is the only histogram type in this scenario that the Cribl Stream OpenTelemetry Source does not support.
• Explicit-bucket histogram metrics are supported by the Cribl Stream OpenTelemetry Source.

Additional Information

• See the Cribl Stream OpenTelemetry Source documentation for Source configuration and troubleshooting options.
• See the OpenTelemetry OTLP metrics exporter specification for supported histogram aggregation environment-variable values.