gRPC trace context extraction from metadata

The gRPC OpenTelemetry interceptor extracts trace context from gRPC metadata using OpenTelemetry propagators. If upstream services don't inject trace context into metadata, distributed traces will be fragmented.

Ensure upstream gRPC clients inject trace context into metadata using OpenTelemetry propagators. Verify trace IDs are propagating across service boundaries by checking span parent relationships in your tracing backend. Configure tracing.excluded_urls to exclude paths that should not be traced.