danvega/ot

Purpose and runtime

This is a Java 17+ Spring Boot 4 demo of the official OpenTelemetry starter. It exposes simple HTTP endpoints while demonstrating automatic OTLP export of traces, metrics, and logs to a vendor-neutral observability backend. Maven is the build/runtime entry point; the application is launched through src/main/java/dev/danvega/ot/Application.java.

HTTP application surface

HomeController is the primary business-facing boundary, serving GET /, GET /greet/{name}, and GET /slow. The greeting and delayed paths create observable request work and application logs, allowing generated telemetry to be inspected end-to-end.

• src/main/java/dev/danvega/ot/HomeController.java

• src/main/java/dev/danvega/ot/Application.java

Spring Boot observability pipeline

Spring Boot auto-configuration, driven by the OpenTelemetry starter declared in pom.xml, instruments inbound HTTP requests and integrates Micrometer tracing with OpenTelemetry. Requests become traces/spans; framework/application metrics are emitted through OTLP; trace context is made available to logging.

• pom.xml

• src/main/resources/application.yaml

Logging-to-OTLP bridge

Logback writes both normal console output and events to the OpenTelemetry Logback appender. The appender requires the Spring-managed OpenTelemetry SDK instance, so a lifecycle bean installs that instance after context initialization. This is the explicit custom integration required beyond starter auto-configuration.

• src/main/resources/logback-spring.xml

• src/main/java/dev/danvega/ot/InstallOpenTelemetryAppender.java

Telemetry configuration boundary

application.yaml establishes the application identity and telemetry behavior, including full development trace sampling and OTLP exporter configuration when not supplied by Compose integration. The key boundary is OTLP/HTTP: metrics, traces, and logs leave the process through collector endpoints rather than application-specific vendor SDKs.

• src/main/resources/application.yaml

Local infrastructure and external services

compose.yaml provides the local Grafana LGTM observability stack. Spring Boot Docker Compose integration can detect this service and configure OTLP connectivity automatically. Grafana is the visualization entry point; its backing components are Loki for logs, Tempo for traces, and Mimir/Prometheus-compatible metrics storage.

• compose.yaml

• pom.xml

End-to-end control flow

1. Spring starts Application, creates the web server, OpenTelemetry SDK, exporters, and the appender installation bean.

2. An HTTP request reaches HomeController; automatic server instrumentation creates request spans and timing metrics.

3. Controller logs inherit active trace/span context; Logback sends them to console and the OTEL appender.

4. OTLP exporters transmit traces, metrics, and logs to the LGTM collector.

5. Grafana queries Tempo, Loki, and metrics storage for correlated inspection by service and trace identifiers.