content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.activemq.thread;
  
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.apache.activemq.annotation.Experimental;
  import org.slf4j.Logger;
  
  /**
   * [AMQ-9394] Virtual Thread support
   *
   * JDK 21 introduces experimental virtual thread support which allow detaching of OS threads
   * from JVM threads. This allows the Java VM to continue working on other tasks while waiting
   * for OS operations (specifically I/O) to complete.
   *
   * JDK 25 provides improvements to Virtual Threads to prevent thread pinning in code blocks
   * that use synchronized.
   *
   * ActiveMQ support for Virtual Threads is currently experimental and profiling of various
   * scenarios and end-user feedback is needed to identify hotspots in order to realize
   * the full performance benefit.
   *
   * Additionally, usage to ThreadLocal needs to be removed/refactored to use ScopedValue
   * or another approach altogether. ActiveMQ has only a few ThreadLocal usages, but a key
   * area is SSLContext support. JIRA [AMQ-9753] will SSL Context ThreadLocal usage.
   *
   * Status:
   * v6.2.0 - Experimental Virtual Thread support introduced.
   *
   */
  @Experimental("Tech Preview for Virtual Thread support")
  public class VirtualThreadExecutor {
  
      private VirtualThreadExecutor() {}
  
      public static ExecutorService createVirtualThreadExecutorService(final String name, final AtomicLong id, final Logger LOG) {
  
          // [AMQ-9394] NOTE: Submitted JDK feature enhancement id: 9076243 to allow AtomicLong thread id param
          // https://bugs.java.com/bugdatabase/view_bug?bug_id=JDK-8320377
          Thread.Builder.OfVirtual threadBuilderOfVirtual = Thread.ofVirtual()
                  .name(name)
                  .uncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
                  @Override
                      public void uncaughtException(final Thread t, final Throwable e) {
                          LOG.error("Error in thread '{}'", t.getName(), e);
                      }
                  });
  
          // [AMQ-9394] Work around to have global thread id increment across ThreadFactories
          ThreadFactory virtualThreadFactory = threadBuilderOfVirtual.factory();
          ThreadFactory atomicThreadFactory = new ThreadFactory() {
              @Override
              public Thread newThread(Runnable r) {
                  Thread tmpThread = virtualThreadFactory.newThread(r);
                  tmpThread.setName(tmpThread.getName() + id.incrementAndGet());
                  return tmpThread;
              }
          };
  
          return Executors.newThreadPerTaskExecutor(atomicThreadFactory); // [AMQ-9394] Same as newVirtualThreadPerTaskExecutor
      }
  }
  