FullJitterBackoffStrategy zero check (#4809)

* Fix IllegalArgumentException in FullJitterBackoffStrategy when base delay and max backoff time are zero.

Author: debora-ito

.changes/next-release/bugfix-AWSSDKforJavav2-daafab1.json

@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Fix IllegalArgumentException in FullJitterBackoffStrategy when base delay and max backoff time are zero."
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/retry/backoff/FullJitterBackoffStrategy.java

@@ -61,8 +61,7 @@ private FullJitterBackoffStrategy(BuilderImpl builder) {
     @Override
     public Duration computeDelayBeforeNextRetry(RetryPolicyContext context) {
         int ceil = calculateExponentialDelay(context.retriesAttempted(), baseDelay, maxBackoffTime);
-        // Minimum of 1 ms (consistent with BackoffStrategy.none()'s behavior)
-        return Duration.ofMillis(random.nextInt(ceil) + 1L);
+        return ceil == 0 ? Duration.ofMillis(0L) : Duration.ofMillis(random.nextInt(ceil) + 1L);
     }
 
     @Override

core/sdk-core/src/test/java/software/amazon/awssdk/core/retry/RetryPolicyTest.java

@@ -185,4 +185,16 @@ public void fastFailRateLimitingConfigured_retryModeAdaptive_doesNotThrow() {
     public void hashCodeDoesNotThrow() {
         RetryPolicy.defaultRetryPolicy().hashCode();
     }
+
+    @Test
+    public void fullJitter_zeroBackoffTimeZeroDelayZeroRetries_delayShouldBeZero() {
+        RetryPolicyContext context = RetryPolicyContext.builder()
+                                                       .retriesAttempted(0)
+                                                       .build();
+        FullJitterBackoffStrategy strategy = FullJitterBackoffStrategy.builder()
+                                                            .baseDelay(Duration.ZERO)
+                                                            .maxBackoffTime(Duration.ZERO)
+                                                            .build();
+        assertThat(strategy.computeDelayBeforeNextRetry(context)).isEqualTo(Duration.ofMillis(0L));
+    }
 }

utils/src/main/java/software/amazon/awssdk/utils/Validate.java

@@ -757,11 +757,11 @@ public static Long isPositiveOrNull(Long num, String fieldName) {
     }
 
     /**
-     * Asserts that the given duration is positive (non-negative and non-zero).
+     * Asserts that the given duration is positive, including zero.
      *
      * @param duration Number to validate
      * @param fieldName Field name to display in exception message if not positive.
-     * @return Duration if positive.
+     * @return Duration if positive or zero.
      */
     public static Duration isNotNegative(Duration duration, String fieldName) {
         if (duration == null) {