I have created an Open Telemetry instrument extension (following this) to trace all method call to any interfaces in a package. However the interface method is not traced by OTEL.

This is the InstrumentationModule class:

@AutoService(InstrumentationModule.class)
public class JMoquiInterfacesInstrumentationModule  extends InstrumentationModule {

    protected final static Logger logger = LoggerFactory.getLogger(JMoquiInterfacesInstrumentationModule.class);

    public JMoquiInterfacesInstrumentationModule() {
        super("jmoqui-demo", "jmoqui-99");
        logger.info("JMoquiInterfacesInstrumentationModule instantiated");
    }

    /*
    We want this instrumentation to be applied after the standard servlet instrumentation.
    The latter creates a server span around http request.
    This instrumentation needs access to that server span.
     */
    @Override
    public int order() {
        return 1;
    }

    @Override
    public ElementMatcher.Junction<ClassLoader> classLoaderMatcher() {
        return AgentElementMatchers.hasClassesNamed("org.moqui.Moqui");
    }

    @Override
    public List<TypeInstrumentation> typeInstrumentations() {
        return singletonList(new JMoquiInterfacesInstrumentation());
    }
}

And this is the custom TypeInstrumentation class:

public class JMoquiInterfacesInstrumentation implements TypeInstrumentation {

    protected final static Logger logger = LoggerFactory.getLogger(JMoquiInterfacesInstrumentation.class);

    @Override
    public ElementMatcher<TypeDescription> typeMatcher() {
        logger.info("typeMatcher");
        return AgentElementMatchers.implementsInterface(
                new NameMatcher<>(new StringMatcher("org.moqui", StringMatcher.Mode.STARTS_WITH) {
                    @Override
                    protected boolean doMatch(String target) {
                        boolean match = super.doMatch(target);
                        if (match) logger.info("doMatch, match: {}", target);
                        return match;
                    }
                })
        );
    }

    @Override
    public void transform(TypeTransformer typeTransformer) {
        logger.info("transform");
        typeTransformer.applyAdviceToMethod(
                any(),
                this.getClass().getName() + "$JMoquiItfAdvice");
    }

    @SuppressWarnings("unused")
    public static class JMoquiItfAdvice {

        protected final static Logger logger = LoggerFactory.getLogger(JMoquiItfAdvice.class);
        private static final Tracer tracer = GlobalOpenTelemetry.getTracer("method-call-tracer");

        @Advice.OnMethodEnter
        public static void onEnter(@Advice.Origin String method) {
            logger.info("onEnter: {}", method);
            Span span = tracer.spanBuilder(method).startSpan();
            span.makeCurrent();
        }

        @Advice.OnMethodExit(onThrowable = Throwable.class)
        public static void onExit(@Advice.Thrown Throwable throwable) {
            Span span = Span.current();
            if (throwable != null) {
                span.recordException(throwable);
            }
            logger.info("onExit");
            span.end();
        }
    }
}

However the onEnter and onExit never printed. After activating otel debug, this WARN showed:

00:35:03.651 [main] INFO com.example.javaagent.instrumentation.JMoquiInterfacesInstrumentation -- doMatch, match: org.moqui.context.L10nFacade
00:35:03.651 [main] INFO com.example.javaagent.instrumentation.JMoquiInterfacesInstrumentation -- doMatch, match: org.moqui.context.LogEventSubscriber
[otel.javaagent 2024-07-15 00:35:03:636 +0800] [main] WARN io.opentelemetry.javaagent.tooling.instrumentation.MuzzleMatcher - Instrumentation skipped, mismatched references were found: jmoqui-demo [class com.example.javaagent.instrumentation.JMoquiInterfacesInstrumentationModule] on jdk.internal.loader.ClassLoaders$AppClassLoader@76ed5528
[otel.javaagent 2024-07-15 00:35:03:636 +0800] [main] WARN io.opentelemetry.javaagent.tooling.instrumentation.MuzzleMatcher - -- com.example.javaagent.instrumentation.JMoquiInterfacesInstrumentation$JMoquiItfAdvice:0 Missing class com.example.javaagent.instrumentation.JMoquiInterfacesInstrumentation$JMoquiItfAdvice
00:35:03.667 [main] INFO com.example.javaagent.instrumentation.JMoquiInterfacesInstrumentation -- doMatch, match: org.moqui.context.LoggerFacade
00:35:03.667 [main] INFO com.example.javaagent.instrumentation.JMoquiInterfacesInstrumentation -- doMatch, match: org.moqui.context.MessageFacade

The logs from JMoquiInterfacesInstrumentation are correctly shown, however JMoquiInterfacesInstrumentation.JMoquiItfAdvice class is reported missing.

The questions are:

1. How to fix the missing class?
2. The “method-call-tracer” on JMoquiItfAdvice is copied over from the example. How does “method-call-tracer” suddenly exists, what does it signifies?

private static final Tracer tracer = GlobalOpenTelemetry.getTracer("method-call-tracer");