opamp-javaagent

opamp-javaagent

An extension for the upstream OpenTelemetry Java agent that puts the agent under an OpAMP server.

Quickstart

Build the extension jar from the repository root (until it is published), then start the application with the agent and the extension, with the server's address and enrollment key:

mvn -q -B -DskipTests install -f java/opamp/pom.xml
mvn -q -B -DskipTests package -f java/opamp-javaagent/pom.xml
OTEL_SERVICE_NAME=checkout \
OTEL_OPAMP_ENDPOINT=https://opamp.example.com/v1/opamp \
OTEL_OPAMP_HEADERS="Authorization=Bearer%20<enrollment key>" \
java -javaagent:opentelemetry-javaagent.jar \
     -Dotel.javaagent.extensions=java/opamp-javaagent/target/opamp-javaagent-extension-0.1.0-SNAPSHOT.jar \
     -jar checkout.jar

When it works, the logger dev.pydantic.opamp.javaagent.Extension says, at INFO (shown by default):

OpAMP: connected to https://opamp.example.com/v1/opamp; this SDK is managed as checkout, instance <uid>

When it can't connect, it warns once, with what to check. The instance keeps its UID across restarts with no configuration (default-state-dir.md).

The server can also send the application settings of its own (a feature flag, a limit). The application reads them with dev.pydantic.opamp.AppSettings, from the second jar the build makes, target/opamp-javaagent-extension-0.1.0-SNAPSHOT-app-settings.jar, which it compiles against and runs with; without the agent every read is its default. A release publishes it beside the extension, as dev.pydantic:opamp-javaagent-extension with the classifier app-settings:

if (AppSettings.get("checkout.new_flow", "off").equals("on")) { ... }
AutoCloseable subscription = AppSettings.onChange((settings, changed) -> queue.add(changed));

Everything else is in docs/javaagent.md, this in its own section.