# boot42-otel

Companion module for the ankurm.com article *Spring Boot 4.2 OpenTelemetry: Semantic Conventions, Shared OTLP Settings and MDC Keys*.
Everything runs against **Spring Boot 4.2.0-RC1** (a release candidate, **not GA**) and against **4.1.2** (GA) as the baseline. JDK 25.

| Path | What it is |
|---|---|
| `pom.xml` / `pom-41.xml` | the same project on 4.2.0-RC1 and on 4.1.2 |
| `src/main/.../OtelApplication` | one endpoint, `GET /hello/{name}`, that logs a line |
| `src/test/.../OtlpSink` | a 60-line OTLP/HTTP receiver: records path, headers and payload strings of every export request |
| `src/test/.../ConventionsTest` | meters and span names for each `management.observations.conventions` value, including the start-up failure RC1 gives for `open-telemetry` |
| `src/test/.../ConventionSpellingsTest` | seven spellings of the conventions value, each started for real: which start and which meter they produce |
| `src/test/.../SharedOtlpTest` | `management.opentelemetry.otlp.*`: paths, merged headers, gzip, and signal-specific overrides |
| `src/test/.../MdcAndLongTaskTimerTest` | custom MDC keys, and the active-observation LongTaskTimer that is no longer on by default |
| `src/test/.../PrometheusNamesTest` | the `http_server_*` names a dashboard query sees under each convention |
| `output/` | every transcript quoted in the article; `./scripts/run-all.sh` regenerates them |

Run: `./scripts/run-all.sh`. `ConventionsTest` pins the RC1 behaviour on purpose; when a later build changes it, that test fails and the article needs updating.

There is deliberately no `docs/` folder: the explanations live in the article.