A metric silently loses data. A sampler setting is accepted but ignored. An HTTP sender has a failure mode you would not expect from infrastructure code.

In this Java-focused talk, we debug real issues from OpenTelemetry Java: asynchronous-metric data loss, ignored sampler configuration, and HTTP telemetry-export reliability or security problems. We will trace the relevant SDK code, reduce each failure, and look at how fixes and tests address them.

The goal is not to teach OpenTelemetry setup or Spring Boot instrumentation. It is to show Java developers how small implementation and configuration bugs inside a dependency can undermine the telemetry they trust, and how to investigate infrastructure libraries instead of treating them as black boxes. The examples are grounded in issues and fixes I contributed to OpenTelemetry Java. Basic Java knowledge is enough; no OpenTelemetry experience is required.