Introduce onRetryPolicyInterruption() callback in RetryListener

In RetryTemplate, if we encounter an InterruptedException while
sleeping for the configured back-off duration, we throw a
RetryException with the InterruptedException as the cause.

However, prior to this commit, that RetryException propagated to the
caller without notifying the registered RetryListener.

To address that, this commit introduces a new
onRetryPolicyInterruption() callback in RetryListener as a companion to
the existing onRetryPolicyExhaustion() callback.

Closes gh-35442

spring-core/src/test/java/org/springframework/core/retry/RetryTemplateTests.java

@@ -30,8 +30,11 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments.ArgumentSet;
 import org.junit.jupiter.params.provider.FieldSource;
+import org.junit.platform.commons.util.ExceptionUtils;
 import org.mockito.InOrder;
 
+import org.springframework.util.backoff.BackOff;
+
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.junit.jupiter.params.provider.Arguments.argumentSet;
@@ -213,6 +216,36 @@ class RetryTemplateTests {
 		verifyNoMoreInteractions(retryListener);
 	}
 
+	@Test
+	void retryWithInterruptionDuringSleep() {
+		Exception exception = new RuntimeException("Boom!");
+		InterruptedException interruptedException = new InterruptedException();
+
+		// Simulates interruption during sleep:
+		BackOff backOff = () -> () -> {
+			throw ExceptionUtils.throwAsUncheckedException(interruptedException);
+		};
+
+		RetryPolicy retryPolicy = RetryPolicy.builder().backOff(backOff).build();
+		RetryTemplate retryTemplate = new RetryTemplate(retryPolicy);
+		retryTemplate.setRetryListener(retryListener);
+		Retryable<String> retryable = () -> {
+			throw exception;
+		};
+
+		assertThatExceptionOfType(RetryException.class)
+				.isThrownBy(() -> retryTemplate.execute(retryable))
+				.withMessageMatching("Unable to back off for retryable operation '.+?'")
+				.withCause(interruptedException)
+				.satisfies(throwable -> assertThat(throwable.getSuppressed()).containsExactly(exception))
+				// TODO Fix retry count for InterruptedException scenario.
+				// Retry count should actually be 0.
+				.satisfies(throwable -> assertThat(throwable.getRetryCount()).isEqualTo(1))
+				.satisfies(throwable -> inOrder.verify(retryListener).onRetryPolicyInterruption(retryPolicy, retryable, throwable));
+
+		verifyNoMoreInteractions(retryListener);
+	}
+
 	@Test
 	void retryWithFailingRetryableAndMultiplePredicates() {
 		var invocationCount = new AtomicInteger();

spring-core/src/test/java/org/springframework/core/retry/support/CompositeRetryListenerTests.java

@@ -92,4 +92,14 @@ class CompositeRetryListenerTests {
 		verify(listener3).onRetryPolicyExhaustion(retryPolicy, retryable, exception);
 	}
 
+	@Test
+	void onRetryPolicyInterruption() {
+		RetryException exception = new RetryException("", new Exception());
+		compositeRetryListener.onRetryPolicyInterruption(retryPolicy, retryable, exception);
+
+		verify(listener1).onRetryPolicyInterruption(retryPolicy, retryable, exception);
+		verify(listener2).onRetryPolicyInterruption(retryPolicy, retryable, exception);
+		verify(listener3).onRetryPolicyInterruption(retryPolicy, retryable, exception);
+	}
+
 }