Accept zero for RetryPolicy.Builder.delay()

This aligns the programmatic RetryPolicy configuration option with the
delay support in @⁠Retryable.

See gh-35110

Author: sbrannen

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

@@ -111,7 +111,7 @@
 	 * this serves as the initial delay to multiply from.
 	 * <p>The time unit is milliseconds by default but can be overridden via
 	 * {@link #timeUnit}.
-	 * <p>The default is 1000.
+	 * <p>Must be greater than or equal to zero. The default is 1000.
 	 * @see #jitter()
 	 * @see #multiplier()
 	 * @see #maxDelay()

spring-core/src/main/java/org/springframework/core/retry/RetryPolicy.java

@@ -209,14 +209,15 @@ public Builder maxAttempts(long maxAttempts) {
 		 * <p>You should not specify this configuration option if you have
 		 * configured a custom {@link #backOff(BackOff) BackOff} strategy.
 		 * @param delay the base delay, typically in milliseconds or seconds;
-		 * must be positive
+		 * must be greater than or equal to zero
 		 * @return this {@code Builder} instance for chained method invocations
 		 * @see #jitter(Duration)
 		 * @see #multiplier(double)
 		 * @see #maxDelay(Duration)
 		 */
 		public Builder delay(Duration delay) {
-			assertIsPositive("delay", delay);
+			Assert.isTrue(!delay.isNegative(),
+					() -> "Invalid delay (%dms): must be >= 0.".formatted(delay.toMillis()));
 			this.delay = delay;
 			return this;
 		}
@@ -233,7 +234,8 @@ public Builder delay(Duration delay) {
 		 * <p>The supplied value will override any previously configured value.
 		 * <p>You should not specify this configuration option if you have
 		 * configured a custom {@link #backOff(BackOff) BackOff} strategy.
-		 * @param jitter the jitter value, typically in milliseconds; must be positive
+		 * @param jitter the jitter value, typically in milliseconds; must be
+		 * greater than or equal to zero
 		 * @return this {@code Builder} instance for chained method invocations
 		 * @see #delay(Duration)
 		 * @see #multiplier(double)

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

@@ -25,6 +25,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
+import static org.springframework.core.retry.RetryPolicy.Builder.DEFAULT_DELAY;
 import static org.springframework.util.backoff.BackOffExecution.STOP;
 
 /**
@@ -38,14 +39,14 @@ class MaxAttemptsRetryPolicyTests {
 
 	@Test
 	void maxAttempts() {
-		var retryPolicy = RetryPolicy.builder().maxAttempts(2).delay(Duration.ofMillis(1)).build();
+		var retryPolicy = RetryPolicy.builder().maxAttempts(2).delay(Duration.ofMillis(0)).build();
 		var backOffExecution = retryPolicy.getBackOff().start();
 		var throwable = mock(Throwable.class);
 
 		assertThat(retryPolicy.shouldRetry(throwable)).isTrue();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isZero();
 		assertThat(retryPolicy.shouldRetry(throwable)).isTrue();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isZero();
 
 		assertThat(retryPolicy.shouldRetry(throwable)).isTrue();
 		assertThat(backOffExecution.nextBackOff()).isEqualTo(STOP);
@@ -65,13 +66,13 @@ void maxAttemptsAndPredicate() {
 
 		// 4 retries
 		assertThat(retryPolicy.shouldRetry(new NumberFormatException())).isTrue();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(1);
 		assertThat(retryPolicy.shouldRetry(new IllegalStateException())).isFalse();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(1);
 		assertThat(retryPolicy.shouldRetry(new IllegalStateException())).isFalse();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(1);
 		assertThat(retryPolicy.shouldRetry(new CustomNumberFormatException())).isTrue();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(1);
 
 		// After policy exhaustion
 		assertThat(retryPolicy.shouldRetry(new NumberFormatException())).isTrue();
@@ -92,17 +93,17 @@ void maxAttemptsWithIncludesAndExcludes() {
 
 		// 6 retries
 		assertThat(retryPolicy.shouldRetry(new IOException())).isTrue();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(DEFAULT_DELAY);
 		assertThat(retryPolicy.shouldRetry(new RuntimeException())).isTrue();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(DEFAULT_DELAY);
 		assertThat(retryPolicy.shouldRetry(new FileNotFoundException())).isFalse();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(DEFAULT_DELAY);
 		assertThat(retryPolicy.shouldRetry(new FileSystemException("file"))).isTrue();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(DEFAULT_DELAY);
 		assertThat(retryPolicy.shouldRetry(new CustomFileSystemException("file"))).isFalse();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(DEFAULT_DELAY);
 		assertThat(retryPolicy.shouldRetry(new IOException())).isTrue();
-		assertThat(backOffExecution.nextBackOff()).isGreaterThan(0);
+		assertThat(backOffExecution.nextBackOff()).isEqualTo(DEFAULT_DELAY);
 
 		// After policy exhaustion
 		assertThat(retryPolicy.shouldRetry(new IOException())).isTrue();

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

@@ -162,12 +162,9 @@ void maxAttempts() {
 
 		@Test
 		void delayPreconditions() {
-			assertThatIllegalArgumentException()
-					.isThrownBy(() -> RetryPolicy.builder().delay(Duration.ofMillis(0)))
-					.withMessage("Invalid duration (0ms): delay must be positive.");
 			assertThatIllegalArgumentException()
 					.isThrownBy(() -> RetryPolicy.builder().delay(Duration.ofMillis(-1)))
-					.withMessage("Invalid duration (-1ms): delay must be positive.");
+					.withMessage("Invalid delay (-1ms): must be >= 0.");
 		}
 
 		@Test

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

@@ -51,7 +51,7 @@ class RetryTemplateTests {
 	void configureRetryTemplate() {
 		var retryPolicy = RetryPolicy.builder()
 				.maxAttempts(3)
-				.delay(Duration.ofMillis(1))
+				.delay(Duration.ofMillis(0))
 				.build();
 
 		retryTemplate.setRetryPolicy(retryPolicy);
@@ -171,7 +171,7 @@ public String getName() {
 
 		var retryPolicy = RetryPolicy.builder()
 				.maxAttempts(Integer.MAX_VALUE)
-				.delay(Duration.ofMillis(1))
+				.delay(Duration.ofMillis(0))
 				.includes(IOException.class)
 				.build();
 
@@ -194,13 +194,13 @@ public String getName() {
 			argumentSet("Excludes",
 						RetryPolicy.builder()
 							.maxAttempts(Integer.MAX_VALUE)
-							.delay(Duration.ofMillis(1))
+							.delay(Duration.ofMillis(0))
 							.excludes(FileNotFoundException.class)
 							.build()),
 			argumentSet("Includes & Excludes",
 						RetryPolicy.builder()
 							.maxAttempts(Integer.MAX_VALUE)
-							.delay(Duration.ofMillis(1))
+							.delay(Duration.ofMillis(0))
 							.includes(IOException.class)
 							.excludes(FileNotFoundException.class)
 							.build())