PR feedback

Author: nhachicha

driver-core/src/main/com/mongodb/internal/time/ExponentialBackoff.java

@@ -42,15 +42,15 @@ private ExponentialBackoff() {
     /**
      * Calculate the backoff in milliseconds for transaction retries.
      *
-     * @param attemptNumber The 0-based attempt number
+     * @param attemptNumber The attempt number
      * @return The calculated backoff in milliseconds.
      */
     public static long calculateTransactionBackoffMs(final int attemptNumber) {
         double jitter = testJitterSupplier != null
                 ? testJitterSupplier.getAsDouble()
                 : ThreadLocalRandom.current().nextDouble();
         return Math.round(jitter * Math.min(
-                TRANSACTION_BASE_MS * Math.pow(TRANSACTION_GROWTH, attemptNumber),
+                TRANSACTION_BASE_MS * Math.pow(TRANSACTION_GROWTH, attemptNumber - 1),
                 TRANSACTION_MAX_MS));
     }
 

…odb/internal/ExponentialBackoffTest.java …nternal/time/ExponentialBackoffTest.javadriver-core/src/test/unit/com/mongodb/internal/ExponentialBackoffTest.java renamed to driver-core/src/test/unit/com/mongodb/internal/time/ExponentialBackoffTest.java driver-core/src/test/unit/com/mongodb/internal/ExponentialBackoffTest.java renamed to driver-core/src/test/unit/com/mongodb/internal/time/ExponentialBackoffTest.java

@@ -14,9 +14,8 @@
  * limitations under the License.
  */
 
-package com.mongodb.internal;
+package com.mongodb.internal.time;
 
-import com.mongodb.internal.time.ExponentialBackoff;
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -31,17 +30,18 @@ void testTransactionRetryBackoff() {
         // With jitter, actual values will be between 0 and these maxima
         double[] expectedMaxValues = {5.0, 7.5, 11.25, 16.875, 25.3125, 37.96875, 56.953125, 85.4296875, 128.14453125, 192.21679688, 288.32519531, 432.48779297, 500.0};
 
-        for (int attemptNumber = 0; attemptNumber < expectedMaxValues.length; attemptNumber++) {
+        for (int attemptNumber = 1; attemptNumber <= expectedMaxValues.length; attemptNumber++) {
             long backoff = ExponentialBackoff.calculateTransactionBackoffMs(attemptNumber);
-            assertTrue(backoff >= 0 && backoff <= Math.round(expectedMaxValues[attemptNumber]),
-                String.format("Attempt %d: backoff should be 0-%d ms, got: %d", attemptNumber, Math.round(expectedMaxValues[attemptNumber]), backoff));
+            assertTrue(backoff >= 0 && backoff <= Math.round(expectedMaxValues[attemptNumber - 1]),
+                String.format("Attempt %d: backoff should be 0-%d ms, got: %d", attemptNumber,
+                        Math.round(expectedMaxValues[attemptNumber - 1]), backoff));
         }
     }
 
     @Test
     void testTransactionRetryBackoffRespectsMaximum() {
         // Even at high attempt numbers, backoff should never exceed 500ms
-        for (int attemptNumber = 0; attemptNumber < 25; attemptNumber++) {
+        for (int attemptNumber = 1; attemptNumber < 26; attemptNumber++) {
             long backoff = ExponentialBackoff.calculateTransactionBackoffMs(attemptNumber);
             assertTrue(backoff >= 0 && backoff <= 500,
                 String.format("Attempt %d: backoff should be capped at 500 ms, got: %d ms", attemptNumber, backoff));
@@ -56,9 +56,9 @@ void testCustomJitter() {
         // Test with jitter = 1.0
         ExponentialBackoff.setTestJitterSupplier(() -> 1.0);
         try {
-            for (int attemptNumber = 0; attemptNumber < expectedBackoffs.length; attemptNumber++) {
+            for (int attemptNumber = 1; attemptNumber <= expectedBackoffs.length; attemptNumber++) {
                 long backoff = ExponentialBackoff.calculateTransactionBackoffMs(attemptNumber);
-                long expected = Math.round(expectedBackoffs[attemptNumber]);
+                long expected = Math.round(expectedBackoffs[attemptNumber - 1]);
                 assertEquals(expected, backoff,
                     String.format("Attempt %d: with jitter=1.0, backoff should be %d ms", attemptNumber, expected));
             }

driver-sync/src/main/com/mongodb/client/internal/ClientSessionImpl.java

@@ -382,7 +382,7 @@ private TimeoutContext createTimeoutContext(final TransactionOptions transaction
 
     private static void backoff(final int transactionAttempt,
             final Timeout withTransactionTimeout, final MongoException lastError) {
-        long backoffMs = ExponentialBackoff.calculateTransactionBackoffMs(transactionAttempt - 1);
+        long backoffMs = ExponentialBackoff.calculateTransactionBackoffMs(transactionAttempt);
         withTransactionTimeout.shortenBy(backoffMs, TimeUnit.MILLISECONDS).onExpired(() -> {
             throw lastError;
         });