OpenTelemetry for Java (the Java agent)

The OpenTelemetry Java agent instruments a JVM app without code changes: HTTP servers and clients (Servlet, Spring MVC and WebFlux, JAX-RS, the JDK's own HttpServer and HttpClient, OkHttp, …), JDBC, messaging clients, and the common logging libraries. It reads the standard variables — its default protocol is already http/protobuf.

Tested on 2026-10-24 with java 21.0.12.1, opentelemetry-javaagent 2.32.0: traces passed, logs passed, logs carry the request's trace and span.

Attach the agent#

curl -fsSLO https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/latest/download/opentelemetry-javaagent.jarjava -javaagent:./opentelemetry-javaagent.jar -jar app.jar

latest follows new releases; for production, download a fixed version from the release page and keep it with your build, so a deploy never changes the agent by surprise.

• Start a compiled app (-jar, or -cp … Main). The agent refuses to start inside JDK tools, which includes running a source file directly with java App.java.

• Spring Boot: the same -javaagent flag in front of -jar app.jar.

• Containers and PaaS: when you cannot change the command, set JAVA_TOOL_OPTIONS="-javaagent:/path/to/opentelemetry-javaagent.jar"; the JVM picks it up on start.

Logs#

The agent captures java.util.logging, Logback and Log4j 2 records and sends them as OpenTelemetry log records with the active trace id and span id; your appenders keep writing as before. Belvador's run uses java.util.logging; Logback and Log4j 2 go through the same agent mechanism but are not part of what is marked tested.

Turning instrumentations off#

Each instrumentation has a switch, for example:

export OTEL_INSTRUMENTATION_JDBC_ENABLED=false

With Sentry's Java SDK#

Keep the Sentry SDK for errors with its tracing off, so the agent is the only tracing owner. The sentry-opentelemetry-otlp event processor puts the agent's span ids on those errors — see With Sentry SDKs; that link is not marked tested yet.