Auto-Generated Service Maps Can Hide Gaps in Observability Coverage

A developer using OpenTelemetry's Java agent with Grafana Tempo discovered that an auto-generated service map failed to show an asynchronous Kafka link between two Spring Boot microservices. The missing edge initially suggested a broken message path, but investigation confirmed the notification service was consuming events and writing data correctly. The real issue was that the OTel Java agent, in that specific build and Spring Boot version, was not instrumenting the Kafka client at all, producing zero messaging spans. No errors or warnings were logged, meaning a fully green dashboard gave a false sense of complete tracing coverage. The incident highlights that an absence of alerts does not guarantee observability coverage, and that silent instrumentation gaps can make a working system appear partially unmonitored.