APM OpenTelemetry intake

The OpenTelemetry intake API uses the OpenTelemetry Protocol (OTLP) to send traces, metrics, and logs to the Elastic Stack. OTLP is the default transfer protocol for OpenTelemetry and is supported natively. The Observability Intake Serverless API supports two OTLP communication protocols on the same port: OTLP/HTTP (protobuf) and OTLP/gRPC.