Add concurrency throttle and flexible task callback to SyncTaskExecutor

Closes gh-35460

spring-context/src/main/java/org/springframework/resilience/annotation/ConcurrencyLimit.java

@@ -38,9 +38,11 @@ import org.springframework.core.annotation.AliasFor;
  *
  * <p>This is particularly useful with Virtual Threads where there is generally
  * no thread pool limit in place. For asynchronous tasks, this can be constrained
- * on {@link org.springframework.core.task.SimpleAsyncTaskExecutor}; for
+ * on {@link org.springframework.core.task.SimpleAsyncTaskExecutor}. For
  * synchronous invocations, this annotation provides equivalent behavior through
- * {@link org.springframework.aop.interceptor.ConcurrencyThrottleInterceptor}.
+ * {@link org.springframework.aop.interceptor.ConcurrencyThrottleInterceptor}
+ * Alternatively, consider {@link org.springframework.core.task.SyncTaskExecutor}
+ * and its inherited concurrency throttle (new as of 7.0) for programmatic use.
  *
  * @author Juergen Hoeller
  * @author Hyunsang Han
@@ -49,6 +51,7 @@ import org.springframework.core.annotation.AliasFor;
  * @see EnableResilientMethods
  * @see ConcurrencyLimitBeanPostProcessor
  * @see org.springframework.aop.interceptor.ConcurrencyThrottleInterceptor
+ * @see org.springframework.core.task.SyncTaskExecutor#setConcurrencyLimit
  * @see org.springframework.core.task.SimpleAsyncTaskExecutor#setConcurrencyLimit
  */
 @Target({ElementType.TYPE, ElementType.METHOD})

spring-context/src/test/java/org/springframework/resilience/ConcurrencyLimitTests.java

@@ -59,7 +59,8 @@ class ConcurrencyLimitTests {
 			futures.add(CompletableFuture.runAsync(proxy::concurrentOperation));
 		}
 		CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
-		assertThat(target.counter).hasValue(0);
+		assertThat(target.current).hasValue(0);
+		assertThat(target.counter).hasValue(10);
 	}
 
 	@Test
@@ -166,10 +167,12 @@ class ConcurrencyLimitTests {
 
 	static class NonAnnotatedBean {
 
+		final AtomicInteger current = new AtomicInteger();
+
 		final AtomicInteger counter = new AtomicInteger();
 
 		public void concurrentOperation() {
-			if (counter.incrementAndGet() > 2) {
+			if (current.incrementAndGet() > 2) {
 				throw new IllegalStateException();
 			}
 			try {
@@ -178,7 +181,8 @@ class ConcurrencyLimitTests {
 			catch (InterruptedException ex) {
 				throw new IllegalStateException(ex);
 			}
-			counter.decrementAndGet();
+			current.decrementAndGet();
+			counter.incrementAndGet();
 		}
 	}
 

spring-core/src/main/java/org/springframework/core/task/SyncTaskExecutor.java

@@ -19,12 +19,13 @@ package org.springframework.core.task;
 import java.io.Serializable;
 
 import org.springframework.util.Assert;
+import org.springframework.util.ConcurrencyThrottleSupport;
 
 /**
  * {@link TaskExecutor} implementation that executes each task <i>synchronously</i>
- * in the calling thread.
- *
- * <p>Mainly intended for testing scenarios.
+ * in the calling thread. This can be used for testing purposes but also for
+ * bounded execution in a Virtual Threads setup, relying on concurrency throttling
+ * as inherited from the base class: see {@link #setConcurrencyLimit} (as of 7.0).
  *
  * <p>Execution in the calling thread does have the advantage of participating
  * in its thread context, for example the thread context class loader or the
@@ -37,17 +38,52 @@ import org.springframework.util.Assert;
  * @see SimpleAsyncTaskExecutor
  */
 @SuppressWarnings("serial")
-public class SyncTaskExecutor implements TaskExecutor, Serializable {
+public class SyncTaskExecutor extends ConcurrencyThrottleSupport implements TaskExecutor, Serializable {
 
 	/**
-	 * Executes the given {@code task} synchronously, through direct
-	 * invocation of it's {@link Runnable#run() run()} method.
-	 * @throws IllegalArgumentException if the given {@code task} is {@code null}
+	 * Execute the given {@code task} synchronously, through direct
+	 * invocation of its {@link Runnable#run() run()} method.
+	 * @throws RuntimeException if propagated from the given {@code Runnable}
 	 */
 	@Override
 	public void execute(Runnable task) {
-		Assert.notNull(task, "Runnable must not be null");
-		task.run();
+		Assert.notNull(task, "Task must not be null");
+		if (isThrottleActive()) {
+			beforeAccess();
+			try {
+				task.run();
+			}
+			finally {
+				afterAccess();
+			}
+		}
+		else {
+			task.run();
+		}
+	}
+
+	/**
+	 * Execute the given {@code task} synchronously, through direct
+	 * invocation of its {@link TaskCallback#call() call()} method.
+	 * @param <V> the returned value type, if any
+	 * @param <E> the exception propagated, if any
+	 * @throws E if propagated from the given {@code TaskCallback}
+	 * @since 7.0
+	 */
+	public <V, E extends Exception> V execute(TaskCallback<V, E> task) throws E {
+		Assert.notNull(task, "Task must not be null");
+		if (isThrottleActive()) {
+			beforeAccess();
+			try {
+				return task.call();
+			}
+			finally {
+				afterAccess();
+			}
+		}
+		else {
+			return task.call();
+		}
 	}
 
 }

spring-core/src/main/java/org/springframework/core/task/TaskCallback.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2002-present the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.core.task;
+
+import java.util.concurrent.Callable;
+
+/**
+ * Variant of {@link Callable} with a flexible exception signature
+ * that can be adapted in the {@link SyncTaskExecutor#execute(TaskCallback)}
+ * method signature for propagating specific exception types only.
+ *
+ * <p>An implementation of this interface can also be passed into any
+ * {@code Callback}-based method such as {@link AsyncTaskExecutor#submit(Callable)}
+ * or {@link AsyncTaskExecutor#submitCompletable(Callable)}. It is just capable
+ * of adapting to flexible exception propagation in caller signatures as well.
+ *
+ * @author Juergen Hoeller
+ * @since 7.0
+ * @param <V> the returned value type, if any
+ * @param <E> the exception propagated, if any
+ * @see SyncTaskExecutor#execute(TaskCallback)
+ */
+public interface TaskCallback<V, E extends Exception> extends Callable<V> {
+
+	@Override
+	V call() throws E;
+
+}

spring-core/src/test/java/org/springframework/core/task/SyncTaskExecutorTests.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright 2002-present the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.core.task;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIOException;
+import static org.assertj.core.api.Assertions.assertThatNoException;
+
+/**
+ * @author Juergen Hoeller
+ * @since 7.0
+ */
+class SyncTaskExecutorTests {
+
+	@Test
+	void plainExecution() {
+		SyncTaskExecutor taskExecutor = new SyncTaskExecutor();
+
+		ConcurrentClass target = new ConcurrentClass();
+		assertThatNoException().isThrownBy(() -> taskExecutor.execute(target::concurrentOperation));
+		assertThat(taskExecutor.execute(target::concurrentOperationWithResult)).isEqualTo("result");
+		assertThatIOException().isThrownBy(() -> taskExecutor.execute(target::concurrentOperationWithException));
+	}
+
+	@Test
+	void withConcurrencyLimit() {
+		SyncTaskExecutor taskExecutor = new SyncTaskExecutor();
+		taskExecutor.setConcurrencyLimit(2);
+
+		ConcurrentClass target = new ConcurrentClass();
+		List<CompletableFuture<?>> futures = new ArrayList<>(10);
+		for (int i = 0; i < 10; i++) {
+			futures.add(CompletableFuture.runAsync(() -> taskExecutor.execute(target::concurrentOperation)));
+		}
+		CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
+		assertThat(target.current).hasValue(0);
+		assertThat(target.counter).hasValue(10);
+	}
+
+	@Test
+	void withConcurrencyLimitAndResult() {
+		SyncTaskExecutor taskExecutor = new SyncTaskExecutor();
+		taskExecutor.setConcurrencyLimit(2);
+
+		ConcurrentClass target = new ConcurrentClass();
+		List<CompletableFuture<?>> futures = new ArrayList<>(10);
+		for (int i = 0; i < 10; i++) {
+			futures.add(CompletableFuture.runAsync(() ->
+					assertThat(taskExecutor.execute(target::concurrentOperationWithResult)).isEqualTo("result")));
+		}
+		CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
+		assertThat(target.current).hasValue(0);
+		assertThat(target.counter).hasValue(10);
+	}
+
+	@Test
+	void withConcurrencyLimitAndException() {
+		SyncTaskExecutor taskExecutor = new SyncTaskExecutor();
+		taskExecutor.setConcurrencyLimit(2);
+
+		ConcurrentClass target = new ConcurrentClass();
+		List<CompletableFuture<?>> futures = new ArrayList<>(10);
+		for (int i = 0; i < 10; i++) {
+			futures.add(CompletableFuture.runAsync(() ->
+					assertThatIOException().isThrownBy(() -> taskExecutor.execute(target::concurrentOperationWithException))));
+		}
+		CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
+		assertThat(target.current).hasValue(0);
+		assertThat(target.counter).hasValue(10);
+	}
+
+
+	static class ConcurrentClass {
+
+		final AtomicInteger current = new AtomicInteger();
+
+		final AtomicInteger counter = new AtomicInteger();
+
+		public void concurrentOperation() {
+			if (current.incrementAndGet() > 2) {
+				throw new IllegalStateException();
+			}
+			try {
+				Thread.sleep(10);
+			}
+			catch (InterruptedException ex) {
+				throw new IllegalStateException(ex);
+			}
+			current.decrementAndGet();
+			counter.incrementAndGet();
+		}
+
+		public String concurrentOperationWithResult() {
+			concurrentOperation();
+			return "result";
+		}
+
+		public String concurrentOperationWithException() throws IOException {
+			concurrentOperation();
+			throw new IOException();
+		}
+	}
+
+}