Enable Virtual Thread when running on JVM 21 (#7261)

#### What type of PR is this?

/kind improvement
/area core
/milestone 2.20.x

#### What this PR does / why we need it:

This PR enables Virtual Thread for instances running on JVM 21. This won't affect instances running on JVM 17.

References:
- https://spring.io/blog/2023/10/31/what-new-is-coming-in-reactor-core-3-6-0
- https://spring.io/blog/2022/10/11/embracing-virtual-threads
- https://docs.spring.io/spring-boot/3.4/reference/features/task-execution-and-scheduling.html

#### Does this PR introduce a user-facing change?

```release-note
None
```

Dockerfile

@@ -25,4 +25,4 @@ RUN ln -sf /usr/share/zoneinfo/$TZ /etc/localtime \
 
 Expose 8090
 
-ENTRYPOINT ["sh", "-c", "java ${JVM_OPTS} org.springframework.boot.loader.launch.JarLauncher ${0} ${@}"]
+ENTRYPOINT ["sh", "-c", "java -Dreactor.schedulers.defaultBoundedElasticOnVirtualThreads=true ${JVM_OPTS} org.springframework.boot.loader.launch.JarLauncher ${0} ${@}"]

api/src/main/java/run/halo/app/extension/controller/DefaultController.java

@@ -2,15 +2,16 @@ package run.halo.app.extension.controller;
 
 import java.time.Duration;
 import java.time.Instant;
+import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Supplier;
 import java.util.stream.IntStream;
 import lombok.extern.slf4j.Slf4j;
-import org.apache.commons.lang3.concurrent.BasicThreadFactory;
+import org.springframework.boot.system.JavaVersion;
+import org.springframework.boot.task.SimpleAsyncTaskExecutorBuilder;
+import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.dao.OptimisticLockingFailureException;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -32,7 +33,7 @@ public class DefaultController<R> implements Controller {
 
     private volatile boolean started = false;
 
-    private final ExecutorService executor;
+    private final Executor executor;
 
     @Nullable
     private final Synchronizer<R> synchronizer;
@@ -53,6 +54,18 @@ public class DefaultController<R> implements Controller {
         Duration minDelay,
         Duration maxDelay,
         ExecutorService executor, int workerCount) {
+        this(name, reconciler, queue, synchronizer, nowSupplier, minDelay, maxDelay,
+            (Executor) executor, workerCount);
+    }
+
+    public DefaultController(String name,
+        Reconciler<R> reconciler,
+        RequestQueue<R> queue,
+        Synchronizer<R> synchronizer,
+        Supplier<Instant> nowSupplier,
+        Duration minDelay,
+        Duration maxDelay,
+        Executor executor, int workerCount) {
         Assert.isTrue(workerCount > 0, "Worker count must not be less than 1");
         this.name = name;
         this.reconciler = reconciler;
@@ -92,15 +105,17 @@ public class DefaultController<R> implements Controller {
         Duration minDelay,
         Duration maxDelay, int workerCount) {
         this(name, reconciler, queue, synchronizer, nowSupplier, minDelay, maxDelay,
-            Executors.newFixedThreadPool(workerCount, threadFactory(name)), workerCount);
+            executor(workerCount, name), workerCount);
     }
 
-    private static ThreadFactory threadFactory(String name) {
-        return new BasicThreadFactory.Builder()
-            .namingPattern(name + "-t-%d")
-            .daemon(false)
-            .uncaughtExceptionHandler((t, e) ->
-                log.error("Controller " + t.getName() + " encountered an error unexpectedly", e))
+    private static SimpleAsyncTaskExecutor executor(int workerCount, String name) {
+        boolean virtualThreads =
+            JavaVersion.getJavaVersion().isEqualOrNewerThan(JavaVersion.TWENTY_ONE);
+        return new SimpleAsyncTaskExecutorBuilder()
+            .virtualThreads(virtualThreads)
+            .concurrencyLimit(workerCount)
+            .taskTerminationTimeout(Duration.ofSeconds(10))
+            .threadNamePrefix(name + "-")
             .build();
     }
 
@@ -123,7 +138,7 @@ public class DefaultController<R> implements Controller {
         log.info("Starting controller {}", name);
         IntStream.range(0, getWorkerCount())
             .mapToObj(i -> new Worker())
-            .forEach(executor::submit);
+            .forEach(executor::execute);
     }
 
     /**
@@ -226,14 +241,18 @@ public class DefaultController<R> implements Controller {
             synchronizer.dispose();
         }
 
-        executor.shutdownNow();
         try {
-            if (!executor.awaitTermination(10, TimeUnit.SECONDS)) {
+            if (executor instanceof AutoCloseable closeable) {
+                closeable.close();
+                if (Thread.currentThread().isInterrupted()) {
                     log.warn("Wait timeout for controller {} shutdown", name);
                 } else {
                     log.info("Controller {} is disposed", name);
                 }
-        } catch (InterruptedException e) {
+            } else if (executor instanceof ExecutorService executorService) {
+                closeExecutorService(executorService);
+            }
+        } catch (Exception e) {
             log.warn("Interrupted while waiting for controller {} shutdown", name);
         } finally {
             queue.dispose();
@@ -248,4 +267,35 @@ public class DefaultController<R> implements Controller {
     public boolean isStarted() {
         return started;
     }
+
+    /**
+     * Close executor service.
+     * <br>
+     * This method copied from
+     * <a href="https://github.com/openjdk/jdk/blob/890adb6410dab4606a4f26a942aed02fb2f55387/src/java.base/share/classes/java/util/concurrent/ExecutorService.java#L410-L429">ExecutorService#close implemented in JDK 21</a>
+     *
+     * @param executorService executor service to be closed
+     */
+    // TODO Remove this method and use ExecutorService#close instead after using JDK 21 as the
+    // minimum version
+    private static void closeExecutorService(ExecutorService executorService) {
+        boolean terminated = executorService.isTerminated();
+        if (!terminated) {
+            executorService.shutdown();
+            boolean interrupted = false;
+            while (!terminated) {
+                try {
+                    terminated = executorService.awaitTermination(1L, TimeUnit.MINUTES);
+                } catch (InterruptedException e) {
+                    if (!interrupted) {
+                        executorService.shutdownNow();
+                        interrupted = true;
+                    }
+                }
+            }
+            if (interrupted) {
+                Thread.currentThread().interrupt();
+            }
+        }
+    }
 }

api/src/test/java/run/halo/app/extension/controller/DefaultControllerTest.java

@@ -8,8 +8,6 @@ import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyLong;
 import static org.mockito.ArgumentMatchers.argThat;
 import static org.mockito.ArgumentMatchers.eq;
-import static org.mockito.Mockito.doNothing;
-import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
@@ -18,7 +16,7 @@ import static org.mockito.Mockito.when;
 import java.time.Duration;
 import java.time.Instant;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
@@ -235,13 +233,16 @@ class DefaultControllerTest {
 
         verify(synchronizer, times(1)).dispose();
         verify(queue, times(1)).dispose();
-        verify(executor, times(1)).shutdownNow();
+        verify(executor).shutdown();
+        verify(executor, never()).shutdownNow();
         verify(executor, times(1)).awaitTermination(anyLong(), any());
     }
 
     @Test
     void shouldDisposeCorrectlyEvenIfTimeoutAwaitTermination() throws InterruptedException {
-        when(executor.awaitTermination(anyLong(), any())).thenThrow(InterruptedException.class);
+        when(executor.awaitTermination(anyLong(), any()))
+            .thenThrow(InterruptedException.class)
+            .thenReturn(true);
 
         controller.dispose();
 
@@ -250,46 +251,36 @@ class DefaultControllerTest {
 
         verify(synchronizer, times(1)).dispose();
         verify(queue, times(1)).dispose();
+        verify(executor).shutdown();
         verify(executor, times(1)).shutdownNow();
-        verify(executor, times(1)).awaitTermination(anyLong(), any());
+        verify(executor, times(2)).awaitTermination(anyLong(), any());
     }
 
     @Test
-    void shouldStartCorrectly() throws InterruptedException {
-        when(executor.submit(any(Runnable.class))).thenAnswer(invocation -> {
-            doNothing().when(synchronizer).start();
-            when(queue.take()).thenThrow(InterruptedException.class);
-
-            // invoke the task really
-            ((Runnable) invocation.getArgument(0)).run();
-            return mock(Future.class);
-        });
+    void shouldStartCorrectly() {
         controller.start();
-
         assertTrue(controller.isStarted());
         assertFalse(controller.isDisposed());
 
-        verify(executor, times(1)).submit(any(Runnable.class));
-        verify(synchronizer, times(1)).start();
-        verify(queue, times(1)).take();
-        verify(reconciler, times(0)).reconcile(any());
+        verify(executor).execute(any(Runnable.class));
     }
 
     @Test
-    void shouldNotStartWhenDisposed() {
+    void shouldNotStartWhenDisposed() throws InterruptedException {
+        when(executor.awaitTermination(1, TimeUnit.MINUTES)).thenReturn(true);
         controller.dispose();
         controller.start();
         assertFalse(controller.isStarted());
         assertTrue(controller.isDisposed());
 
-        verify(executor, times(0)).submit(any(Runnable.class));
+        verify(executor, times(0)).execute(any(Runnable.class));
     }
 
     @Test
     void shouldCreateMultiWorkers() {
         controller = createController(5);
         controller.start();
-        verify(executor, times(5)).submit(any(DefaultController.Worker.class));
+        verify(executor, times(5)).execute(any(DefaultController.Worker.class));
     }
 
     @Test

application/src/main/resources/application.yaml

@@ -34,6 +34,9 @@ spring:
     type: caffeine
     caffeine:
       spec: expireAfterAccess=1h, maximumSize=10000
+  threads:
+    virtual:
+      enabled: true
 
 halo:
   work-dir: ${user.home}/.halo2