WIP - Show the worst possible workaround for QCL leak in tests

core/runtime/src/main/java/io/quarkus/runtime/ExecutorRecorder.java

@@ -1,5 +1,7 @@
 package io.quarkus.runtime;
 
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
 import java.time.Duration;
 import java.util.List;
 import java.util.Optional;
@@ -33,6 +35,7 @@ public ExecutorRecorder() {
     static volatile CleanableExecutor devModeExecutor;
 
     private static volatile Executor current;
+    private static volatile JBossThreadFactory threadFactory;
 
     public ExecutorService setupRunTime(ShutdownContext shutdownContext, ThreadPoolConfig threadPoolConfig,
             LaunchMode launchMode) {
@@ -84,6 +87,27 @@ private static Runnable createShutdownTask(ThreadPoolConfig threadPoolConfig, En
             @Override
             public void run() {
                 executor.shutdown();
+                try {
+                    //we need to get rid of AccessControlContext from the Executor and the Factory
+
+                    Field modifiersField = Field.class.getDeclaredField("modifiers");
+                    modifiersField.setAccessible(true);
+
+                    Field executorAccField = EnhancedQueueExecutor.class.getDeclaredField("acc");
+                    executorAccField.setAccessible(true);
+                    Field factoryAccField = JBossThreadFactory.class.getDeclaredField("creatingContext");
+                    factoryAccField.setAccessible(true);
+
+                    modifiersField.setInt(executorAccField, executorAccField.getModifiers() & ~Modifier.FINAL);
+                    modifiersField.setInt(factoryAccField, factoryAccField.getModifiers() & ~Modifier.FINAL);
+                    executorAccField.set(executor, null);
+                    factoryAccField.set(threadFactory, null);
+                } catch (NoSuchFieldException | IllegalAccessException ignored) {
+
+                }
+                current = null;
+                threadFactory = null;
+
                 final Duration shutdownTimeout = threadPoolConfig.shutdownTimeout;
                 final Optional<Duration> optionalInterval = threadPoolConfig.shutdownCheckInterval;
                 long remaining = shutdownTimeout.toNanos();
@@ -155,7 +179,7 @@ public void run() {
     }
 
     private static EnhancedQueueExecutor createExecutor(ThreadPoolConfig threadPoolConfig) {
-        final JBossThreadFactory threadFactory = new JBossThreadFactory(new ThreadGroup("executor"), Boolean.TRUE, null,
+        threadFactory = new JBossThreadFactory(new ThreadGroup("executor"), Boolean.TRUE, null,
                 "executor-thread-%t", JBossExecutors.loggingExceptionHandler("org.jboss.executor.uncaught"), null);
         final EnhancedQueueExecutor.Builder builder = new EnhancedQueueExecutor.Builder()
                 .setRegisterMBean(false)

extensions/vertx-core/runtime/src/main/java/io/quarkus/vertx/core/runtime/VertxCoreRecorder.java

@@ -8,6 +8,8 @@
 import static io.vertx.core.file.impl.FileResolver.CACHE_DIR_BASE_PROP_NAME;
 
 import java.io.File;
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -24,8 +26,10 @@
 import org.wildfly.common.cpu.ProcessorInfo;
 
 import io.netty.channel.EventLoopGroup;
+import io.netty.util.concurrent.DefaultPromise;
 import io.netty.util.concurrent.EventExecutor;
 import io.netty.util.concurrent.FastThreadLocal;
+import io.netty.util.concurrent.GlobalEventExecutor;
 import io.quarkus.runtime.IOThreadDetector;
 import io.quarkus.runtime.LaunchMode;
 import io.quarkus.runtime.ShutdownContext;
@@ -293,6 +297,28 @@ void destroy() {
                 throw new IllegalStateException("Exception when closing Vert.x instance", e);
             }
             vertx = null;
+
+            try {
+                // we need to get rid of all Netty fields that use Exceptions to control the flow
+                // because these fields can leak the QCL due to the backtrace field of Throwable
+
+                Field modifiersField = Field.class.getDeclaredField("modifiers");
+                modifiersField.setAccessible(true);
+
+                Field cancellationCauseHolderField = DefaultPromise.class.getDeclaredField("CANCELLATION_CAUSE_HOLDER");
+                cancellationCauseHolderField.setAccessible(true);
+                Field terminationFutureField = GlobalEventExecutor.class.getDeclaredField("terminationFuture");
+                terminationFutureField.setAccessible(true);
+
+                modifiersField.setInt(cancellationCauseHolderField,
+                        cancellationCauseHolderField.getModifiers() & ~Modifier.FINAL);
+                modifiersField.setInt(terminationFutureField,
+                        terminationFutureField.getModifiers() & ~Modifier.FINAL);
+                cancellationCauseHolderField.set(null, null);
+                terminationFutureField.set(GlobalEventExecutor.INSTANCE, null);
+            } catch (NoSuchFieldException | IllegalAccessException ignored) {
+
+            }
         }
     }
 

extensions/vertx-core/runtime/src/main/java/io/quarkus/vertx/core/runtime/config/VertxConfiguration.java

@@ -18,8 +18,11 @@ public class VertxConfiguration {
 
     /**
      * Enables or disabled the Vert.x classpath resource resolver.
+     *
+     * This is set to false because it spawns a thread which then holds on to the QCL
+     * and leads to leaks in tests
      */
-    @ConfigItem(defaultValue = "true")
+    @ConfigItem(defaultValue = "false")
     public boolean classpathResolving;
 
     /**