`SimpleAsyncTaskScheduler` does not apply its `TaskDecorator` to fixed-delay tasks

SimpleAsyncTaskScheduler、特に taskOnSchedulerThread と execute から始め、固定遅延タスクとその他のスケジュール済みタスクの扱いを比較してください。SimpleAsyncTaskSchedulerTests を実行し、issue に記載された固定遅延デコレーターのテストを確認してください。固定遅延タスクにデコレーターが適用され、テストが成功すれば完了です。

SimpleAsyncTaskScheduler runs fixed-delay tasks on its scheduler thread (#31334), wrapped by taskOnSchedulerThread, which adds the error handler but not the TaskDecorator. One-time, fixed-rate and trigger tasks go through execute, where the decorator is applied. ThreadPoolTaskScheduler decorates all of them, fixed-delay included (decorateTask).

So a @Scheduled(fixedDelay = …) method runs without whatever the decorator sets up (MDC, security or context propagation), and nothing warns about it. With Spring Boot it changes when virtual threads are enabled: Boot then creates a SimpleAsyncTaskScheduler instead of a ThreadPoolTaskScheduler, passing the application's TaskDecorator beans to either of them.

The Javadoc of setTaskDecorator says the decorator is "applied to any Runnable about to be executed". The class Javadoc says that fixed-delay tasks run on the single scheduler thread, but not that they skip the decorator.

Affects 7.0.10; the code is the same on main.

Reproducer

Spring Framework 7.0.10 on JDK 25: java -cp <spring-context and its dependencies> FixedDelayTaskDecorator.java

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.scheduling.concurrent.SimpleAsyncTaskScheduler;

public class FixedDelayTaskDecorator {

	// Set by the TaskDecorator around each task, as a context-propagating decorator would do
	static final ThreadLocal<Boolean> decorated = ThreadLocal.withInitial(() -> false);

	static final Map<String, Boolean> results = new ConcurrentHashMap<>();

	static final CountDownLatch latch = new CountDownLatch(2);


	public static void main(String[] args) throws InterruptedException {
		try (var context = new AnnotationConfigApplicationContext(Config.class)) {
			latch.await(5, TimeUnit.SECONDS);
			System.out.println("fixedRate  task decorated: " + results.get("fixedRate"));
			System.out.println("fixedDelay task decorated: " + results.get("fixedDelay"));
		}
	}


	@Configuration
	@EnableScheduling
	static class Config {

		@Bean
		SimpleAsyncTaskScheduler taskScheduler() {
			SimpleAsyncTaskScheduler scheduler = new SimpleAsyncTaskScheduler();
			scheduler.setVirtualThreads(true);
			scheduler.setTaskDecorator(task -> () -> {
				decorated.set(true);
				try {
					task.run();
				}
				finally {
					decorated.remove();
				}
			});
			return scheduler;
		}

		@Bean
		Tasks tasks() {
			return new Tasks();
		}
	}


	static class Tasks {

		@Scheduled(fixedRate = 100)
		void fixedRate() {
			record("fixedRate");
		}

		@Scheduled(fixedDelay = 100)
		void fixedDelay() {
			record("fixedDelay");
		}

		private static void record(String task) {
			if (results.putIfAbsent(task, decorated.get()) == null) {
				latch.countDown();
			}
		}
	}

}

Output:

fixedRate  task decorated: true
fixedDelay task decorated: false

With a ThreadPoolTaskScheduler instead (and no setVirtualThreads), both lines print true.

Possible fix

Keep a reference to the decorator and apply it in taskOnSchedulerThread, around the error handling, as execute does:

--- a/SimpleAsyncTaskScheduler.java
+++ b/SimpleAsyncTaskScheduler.java
@@ -37,6 +37,7 @@
 import org.springframework.context.SmartLifecycle;
 import org.springframework.context.event.ContextClosedEvent;
 import org.springframework.core.task.SimpleAsyncTaskExecutor;
+import org.springframework.core.task.TaskDecorator;
 import org.springframework.core.task.TaskRejectedException;
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.scheduling.Trigger;
@@ -124,6 +125,8 @@
 
 	private @Nullable ErrorHandler errorHandler;
 
+	private @Nullable TaskDecorator taskDecorator;
+
 	private Clock clock = Clock.systemDefaultZone();
 
 	private int phase = DEFAULT_PHASE;
@@ -142,6 +145,12 @@
 		this.errorHandler = errorHandler;
 	}
 
+	@Override
+	public void setTaskDecorator(TaskDecorator taskDecorator) {
+		super.setTaskDecorator(taskDecorator);
+		this.taskDecorator = taskDecorator;
+	}
+
 	/**
 	 * Set the clock to use for scheduling purposes.
 	 * <p>The default clock is the system clock for the default time zone.
@@ -230,8 +239,9 @@
 	}
 
 	private Runnable taskOnSchedulerThread(Runnable task) {
-		return new DelegatingErrorHandlingRunnable(task,
+		Runnable taskToUse = new DelegatingErrorHandlingRunnable(task,
 				(this.errorHandler != null ? this.errorHandler : TaskUtils.getDefaultErrorHandler(true)));
+		return (this.taskDecorator != null ? this.taskDecorator.decorate(taskToUse) : taskToUse);
 	}
 
 	private Runnable scheduledTask(Runnable task) {

With that change on top of 7.0.10, the reproducer prints true twice, and SimpleAsyncTaskSchedulerTests passes together with this test, which fails without it (its buildExecutor() already sets a decorator that flags taskRun):

	@Test
	void scheduleWithFixedDelay() {
		TestTask task = new TestTask(this.testName, 3);
		Future<?> future = scheduler.scheduleWithFixedDelay(task, Duration.ofMillis(10));
		await(task);
		future.cancel(true);
		assertThat(taskRun.get()).isTrue();
	}