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Instrumentation of Java libraries using OpenTelemetry.

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/*
 * Copyright The OpenTelemetry Authors
 * SPDX-License-Identifier: Apache-2.0
 */

package io.opentelemetry.javaagent.instrumentation.undertow;

import static io.opentelemetry.javaagent.extension.matcher.AgentElementMatchers.hasClassesNamed;
import static io.opentelemetry.javaagent.extension.matcher.AgentElementMatchers.implementsInterface;
import static io.opentelemetry.javaagent.instrumentation.undertow.UndertowSingletons.helper;
import static net.bytebuddy.matcher.ElementMatchers.isPublic;
import static net.bytebuddy.matcher.ElementMatchers.named;
import static net.bytebuddy.matcher.ElementMatchers.takesArgument;

import io.opentelemetry.context.Context;
import io.opentelemetry.context.Scope;
import io.opentelemetry.javaagent.bootstrap.Java8BytecodeBridge;
import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
import io.undertow.server.HttpServerExchange;
import net.bytebuddy.asm.Advice;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.matcher.ElementMatcher;

public class HandlerInstrumentation implements TypeInstrumentation {

  @Override
  public ElementMatcher.Junction classLoaderOptimization() {
    return hasClassesNamed("io.undertow.server.HttpHandler");
  }

  @Override
  public ElementMatcher typeMatcher() {
    return implementsInterface(named("io.undertow.server.HttpHandler"));
  }

  @Override
  public void transform(TypeTransformer transformer) {
    transformer.applyAdviceToMethod(
        named("handleRequest")
            .and(takesArgument(0, named("io.undertow.server.HttpServerExchange")))
            .and(isPublic()),
        this.getClass().getName() + "$HandleRequestAdvice");
  }

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

    @Advice.OnMethodEnter(suppress = Throwable.class)
    public static void onEnter(
        @Advice.Argument(0) HttpServerExchange exchange,
        @Advice.Local("otelContext") Context context,
        @Advice.Local("otelScope") Scope scope) {
      Context attachedContext = helper().getServerContext(exchange);
      if (attachedContext != null) {
        if (!Java8BytecodeBridge.currentContext().equals(attachedContext)) {
          // request processing is dispatched to another thread
          scope = attachedContext.makeCurrent();
          context = attachedContext;
          helper().handlerStarted(attachedContext);
        }
        return;
      }

      Context parentContext = Java8BytecodeBridge.currentContext();
      if (!helper().shouldStart(parentContext, exchange)) {
        return;
      }

      context = helper().start(parentContext, exchange);
      scope = context.makeCurrent();

      exchange.addExchangeCompleteListener(new EndSpanListener(context));
    }

    @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
    public static void onExit(
        @Advice.Argument(0) HttpServerExchange exchange,
        @Advice.Thrown Throwable throwable,
        @Advice.Local("otelContext") Context context,
        @Advice.Local("otelScope") Scope scope) {
      if (scope == null) {
        return;
      }
      scope.close();

      helper().handlerCompleted(context, throwable, exchange);
    }
  }
}