Add debug logging to flaky apache async client tests (#13460)

instrumentation/apache-httpclient/apache-httpclient-5.0/javaagent/build.gradle.kts

@@ -17,5 +17,6 @@ dependencies {
 tasks {
   withType<Test>().configureEach {
     systemProperty("testLatestDeps", findProperty("testLatestDeps") as Boolean)
+    systemProperty("otel.instrumentation.apache-httpclient-5.debug", "true")
   }
 }

instrumentation/apache-httpclient/apache-httpclient-5.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/apachehttpclient/v5_0/ApacheHttpClientInstrumentationModule.java

@@ -6,6 +6,7 @@
 package io.opentelemetry.javaagent.instrumentation.apachehttpclient.v5_0;
 
 import com.google.auto.service.AutoService;
+import io.opentelemetry.javaagent.bootstrap.internal.AgentInstrumentationConfig;
 import io.opentelemetry.javaagent.extension.instrumentation.InstrumentationModule;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
 import java.util.Arrays;
@@ -20,6 +21,15 @@ public class ApacheHttpClientInstrumentationModule extends InstrumentationModule
 
   @Override
   public List<TypeInstrumentation> typeInstrumentations() {
+    boolean debug =
+        AgentInstrumentationConfig.get()
+            .getBoolean("otel.instrumentation.apache-httpclient-5.debug", false);
+    if (debug) {
+      return Arrays.asList(
+          new ApacheHttpClientInstrumentation(),
+          new ApacheHttpAsyncClientInstrumentation(),
+          new IoReactorDebugInstrumentation());
+    }
     return Arrays.asList(
         new ApacheHttpClientInstrumentation(), new ApacheHttpAsyncClientInstrumentation());
   }

instrumentation/apache-httpclient/apache-httpclient-5.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/apachehttpclient/v5_0/IoReactorDebugInstrumentation.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.instrumentation.apachehttpclient.v5_0;
+
+import static io.opentelemetry.javaagent.extension.matcher.AgentElementMatchers.implementsInterface;
+import static net.bytebuddy.matcher.ElementMatchers.named;
+import static net.bytebuddy.matcher.ElementMatchers.namedOneOf;
+
+import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
+import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
+import net.bytebuddy.asm.Advice;
+import net.bytebuddy.description.type.TypeDescription;
+import net.bytebuddy.matcher.ElementMatcher;
+
+public class IoReactorDebugInstrumentation implements TypeInstrumentation {
+
+  @Override
+  public ElementMatcher<TypeDescription> typeMatcher() {
+    return implementsInterface(named("org.apache.hc.core5.reactor.IOReactor"));
+  }
+
+  @Override
+  public void transform(TypeTransformer transformer) {
+    transformer.applyAdviceToMethod(
+        namedOneOf("close", "initiateShutdown"), this.getClass().getName() + "$CloseAdvice");
+  }
+
+  @SuppressWarnings("unused")
+  public static class CloseAdvice {
+
+    @SuppressWarnings("SystemOut")
+    @Advice.OnMethodEnter(suppress = Throwable.class)
+    public static void methodEnter(@Advice.This Object instance) {
+      System.err.println("closing i/o reactor " + instance);
+      new Exception().printStackTrace();
+    }
+  }
+}