# 4. Production checklist

Previous: [3. OTEL_* environment variables](03-otel-env-vars.md) | [README](../README.md)

| Item | This module's finding |
|---|---|
| Which starter | `spring-boot-starter-opentelemetry` -- one dependency for OTLP metrics + traces, replacing a per-vendor registry jar plus a tracing bridge |
| Local development | A `compose.yaml` naming `grafana/otel-lgtm` gets auto-wired by Boot's Docker Compose support with zero `management.otlp.*` properties -- verified `127.0.0.1`, not the bare-default `localhost`, in the startup log |
| Any other environment | Set the export endpoint explicitly -- either `management.otlp.*` properties or, as of 4.1, standard `OTEL_EXPORTER_OTLP_*` variables. Auto-wiring is a dev-time convenience only |
| Standard `OTEL_*` env vars | `OTEL_EXPORTER_OTLP_ENDPOINT` worked before 4.1 too (a Micrometer default, not a Boot feature); the rest of the surface -- `OTEL_METRIC_EXPORT_INTERVAL` and friends -- is genuinely new in 4.1 |
| `@Observed` | Needs an explicit `ObservedAspect` @Bean. AspectJ weaving present + Micrometer Tracing active is *not* sufficient on its own -- the annotation is silently inert without it |
| Trace sampling | Defaults to 0.10. Metrics are never sampled. A "why don't my traces show up" question at low local traffic is very often just this |
| Cardinality, context propagation, the Observation API in depth | Already covered start to finish: [Micrometer to OpenTelemetry: The Spring Boot 4 Observability Guide](https://ankurm.com/micrometer-opentelemetry-spring-boot-4-observability-guide/) |

## License

MIT -- part of the [spring-boot-demo](../../) container repository; see [../../LICENSE](../../LICENSE).