Experiment with fully virtual VirtualThreadPool (#11501)

Virtual threads are used for all threading.

jetty-core/jetty-server/src/main/config/etc/jetty-threadpool-all-virtual.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0"?>
+<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN" "https://www.eclipse.org/jetty/configure_10_0.dtd">
+
+<Configure>
+  <New id="threadPool" class="org.eclipse.jetty.util.thread.VirtualThreadPool">
+    <Set name="name" property="jetty.threadPool.namePrefix" />
+  </New>
+
+  <Call class="org.slf4j.LoggerFactory" name="getLogger">
+    <Arg>org.eclipse.jetty</Arg>
+    <Call name="info">
+      <Arg>Virtual threads enabled. Using virtual threads for all tasks.</Arg>
+    </Call>
+  </Call>
+</Configure>

jetty-core/jetty-server/src/main/config/etc/jetty-threadpool-virtual.xml

@@ -37,7 +37,7 @@
   <Call class="org.slf4j.LoggerFactory" name="getLogger">
     <Arg>org.eclipse.jetty</Arg>
     <Call name="info">
-      <Arg>Virtual threads are enabled.</Arg>
+      <Arg>Virtual threads enabled. Using virtual threads for application tasks.</Arg>
     </Call>
   </Call>
 </Configure>

jetty-core/jetty-server/src/main/config/modules/threadpool-all-virtual.mod

@@ -0,0 +1,19 @@
+[description]
+Enables and configures the Server ThreadPool with support for virtual threads to be used for all threads.
+There is some risk of CPU pinning with this configuration.  Only supported in Java 21 or later.
+
+[depends]
+logging
+
+[provides]
+threadpool
+
+[xml]
+etc/jetty-threadpool-all-virtual.xml
+
+[ini-template]
+# tag::documentation[]
+## Platform threads name prefix.
+#jetty.threadPool.namePrefix=vtp<hashCode>
+
+# end::documentation[]

jetty-core/jetty-server/src/main/config/modules/threadpool-virtual.mod

@@ -1,5 +1,6 @@
 [description]
-Enables and configures the Server ThreadPool with support for virtual threads in Java 21 or later.
+Enables and configures the Server ThreadPool with support for virtual threads to be used for blocking tasks.
+Only supported in Java 21 or later.
 
 [depends]
 logging

jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/VirtualThreads.java

@@ -32,21 +32,9 @@
 public class VirtualThreads
 {
     private static final Logger LOG = LoggerFactory.getLogger(VirtualThreads.class);
-    private static final Executor executor = probeVirtualThreadExecutor();
+    private static final Executor executor = getNamedVirtualThreadsExecutor(null);
     private static final Method isVirtualThread = probeIsVirtualThread();
 
-    private static Executor probeVirtualThreadExecutor()
-    {
-        try
-        {
-            return (Executor)Executors.class.getMethod("newVirtualThreadPerTaskExecutor").invoke(null);
-        }
-        catch (Throwable x)
-        {
-            return null;
-        }
-    }
-
     private static Method probeIsVirtualThread()
     {
         try
@@ -131,7 +119,8 @@ public static Executor getNamedVirtualThreadsExecutor(String namePrefix)
         {
             Class<?> builderClass = Class.forName("java.lang.Thread$Builder");
             Object threadBuilder = Thread.class.getMethod("ofVirtual").invoke(null);
-            threadBuilder = builderClass.getMethod("name", String.class, long.class).invoke(threadBuilder, namePrefix, 0L);
+            if (StringUtil.isNotBlank(namePrefix))
+                threadBuilder = builderClass.getMethod("name", String.class, long.class).invoke(threadBuilder, namePrefix, 0L);
             ThreadFactory factory = (ThreadFactory)builderClass.getMethod("factory").invoke(threadBuilder);
             return (Executor)Executors.class.getMethod("newThreadPerTaskExecutor", ThreadFactory.class).invoke(null, factory);
         }

jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/thread/QueuedThreadPool.java

@@ -449,7 +449,7 @@ public void setReservedThreads(int reservedThreads)
     }
 
     /**
-     * @return the name of the this thread pool
+     * @return the name of this thread pool
      */
     @ManagedAttribute("name of the thread pool")
     public String getName()
@@ -460,7 +460,7 @@ public String getName()
     /**
      * <p>Sets the name of this thread pool, used as a prefix for the thread names.</p>
      *
-     * @param name the name of the this thread pool
+     * @param name the name of this thread pool
      */
     public void setName(String name)
     {
@@ -835,7 +835,7 @@ public void join() throws InterruptedException
 
         while (isStopping())
         {
-            Thread.sleep(1);
+            Thread.onSpinWait();
         }
     }
 

jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/thread/TrackingExecutor.java

@@ -0,0 +1,102 @@
+//
+// ========================================================================
+// Copyright (c) 1995 Mort Bay Consulting Pty Ltd and others.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Eclipse Public License v. 2.0 which is available at
+// https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+// which is available at https://www.apache.org/licenses/LICENSE-2.0.
+//
+// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+// ========================================================================
+//
+
+package org.eclipse.jetty.util.thread;
+
+import java.io.IOException;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.Executor;
+
+import org.eclipse.jetty.util.annotation.ManagedAttribute;
+import org.eclipse.jetty.util.annotation.ManagedObject;
+import org.eclipse.jetty.util.component.Dumpable;
+
+@ManagedObject("Tracking Executor wrapper")
+public class TrackingExecutor implements Executor, Dumpable
+{
+    private final Executor _threadFactoryExecutor;
+    private final Set<Thread> _threads = ConcurrentHashMap.newKeySet();
+    private boolean _detailed;
+
+    public TrackingExecutor(Executor executor, boolean detailed)
+    {
+        _threadFactoryExecutor = executor;
+        _detailed = detailed;
+    }
+
+    @Override
+    public void execute(Runnable task)
+    {
+        _threadFactoryExecutor.execute(() ->
+        {
+            Thread thread = Thread.currentThread();
+            try
+            {
+                _threads.add(thread);
+                task.run();
+            }
+            finally
+            {
+                _threads.remove(thread);
+            }
+        });
+    }
+
+    @Override
+    public void dump(Appendable out, String indent) throws IOException
+    {
+        Object[] threads = _threads.stream().map(DumpableThread::new).toArray();
+        Dumpable.dumpObjects(out, indent, _threadFactoryExecutor.toString() + " size=" + threads.length, threads);
+    }
+
+    public void setDetailedDump(boolean detailedDump)
+    {
+        _detailed = detailedDump;
+    }
+
+    @ManagedAttribute("reports additional details in the dump")
+    public boolean isDetailedDump()
+    {
+        return _detailed;
+    }
+
+    public int size()
+    {
+        return _threads.size();
+    }
+
+    private class DumpableThread implements Dumpable
+    {
+        private final Thread _thread;
+
+        private DumpableThread(Thread thread)
+        {
+            _thread = thread;
+        }
+
+        @Override
+        public void dump(Appendable out, String indent) throws IOException
+        {
+            if (_detailed)
+            {
+                Object[] stack = _thread.getStackTrace();
+                Dumpable.dumpObjects(out, indent, _thread.toString(), stack);
+            }
+            else
+            {
+                Dumpable.dumpObject(out, _thread);
+            }
+        }
+    }
+}