Cap max RetryableAction wait time/timeout. (#74940) (#76152)

RetryableAction uses randomized and exponential back off. If unlucky,
the randomization would cause a series of very short waits, which would
double the bound every time, risking a subsequent very long wait. Now
randomize between [bound/2, bound[.

Closes #70996

server/src/main/java/org/elasticsearch/action/support/RetryableAction.java

@@ -103,12 +103,12 @@ public void onRejection(Exception e) {
 
     public abstract boolean shouldRetry(Exception e);
 
-    protected long calculateDelay(long previousDelay) {
-        return Math.min(previousDelay * 2, Integer.MAX_VALUE);
+    protected long calculateDelayBound(long previousDelayBound) {
+        return Math.min(previousDelayBound * 2, Integer.MAX_VALUE);
     }
 
     protected long minimumDelayMillis() {
-        return 1L;
+        return 0L;
     }
 
     public void onFinished() {
@@ -145,10 +145,12 @@ public void onFailure(Exception e) {
                 } else {
                     addException(e);
 
-                    final long nextDelayMillisBound = calculateDelay(delayMillisBound);
+                    final long nextDelayMillisBound = calculateDelayBound(delayMillisBound);
                     final RetryingListener retryingListener = new RetryingListener(nextDelayMillisBound, caughtExceptions);
                     final Runnable runnable = createRunnable(retryingListener);
-                    final long delayMillis = Randomness.get().nextInt(Math.toIntExact(delayMillisBound)) + minimumDelayMillis();
+                    int range = Math.toIntExact((delayMillisBound + 1) / 2);
+                    final long delayMillis = Randomness.get().nextInt(range) + delayMillisBound - range + 1L;
+                    assert delayMillis > 0;
                     if (isDone.get() == false) {
                         final TimeValue delay = TimeValue.timeValueMillis(delayMillis);
                         logger.debug(() -> new ParameterizedMessage("retrying action that failed in {}", delay), e);

server/src/test/java/org/elasticsearch/action/support/RetryableActionTests.java

@@ -102,7 +102,7 @@ public void testRetryableActionTimeout() {
         final AtomicInteger retryCount = new AtomicInteger();
         final PlainActionFuture<Boolean> future = PlainActionFuture.newFuture();
         final RetryableAction<Boolean> retryableAction = new RetryableAction<Boolean>(logger, taskQueue.getThreadPool(),
-            TimeValue.timeValueMillis(10), TimeValue.timeValueSeconds(1), future) {
+            TimeValue.timeValueMillis(randomFrom(1, 10, randomIntBetween(100, 2000))), TimeValue.timeValueSeconds(1), future) {
 
             @Override
             public void tryAction(ActionListener<Boolean> listener) {
@@ -119,6 +119,7 @@ public boolean shouldRetry(Exception e) {
                 return e instanceof EsRejectedExecutionException;
             }
         };
+        long begin = taskQueue.getCurrentTimeMillis();
         retryableAction.run();
         taskQueue.runAllRunnableTasks();
         long previousDeferredTime = 0;
@@ -133,6 +134,10 @@ public boolean shouldRetry(Exception e) {
         assertFalse(taskQueue.hasRunnableTasks());
 
         expectThrows(EsRejectedExecutionException.class, future::actionGet);
+
+        long end = taskQueue.getCurrentTimeMillis();
+        // max 3x timeout since we minimum wait half the bound for every retry.
+        assertThat(end - begin, lessThanOrEqualTo(3000L));
     }
 
     public void testTimeoutOfZeroMeansNoRetry() {

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/utils/persistence/ResultsPersisterService.java

@@ -390,7 +390,6 @@ private abstract class MlRetryableAction<Request, Response> extends RetryableAct
         final Consumer<String> msgHandler;
         final BiConsumer<Request, ActionListener<Response>> action;
         volatile int currentAttempt = 0;
-        volatile long currentMin = MIN_RETRY_SLEEP_MILLIS;
         volatile long currentMax = MIN_RETRY_SLEEP_MILLIS;
 
         MlRetryableAction(String jobId,
@@ -453,30 +452,21 @@ public boolean shouldRetry(Exception e) {
         }
 
         @Override
-        protected long calculateDelay(long previousDelay) {
-            // Since we exponentially increase, we don't want force randomness to have an excessively long sleep
-            if (currentMax < MAX_RETRY_SLEEP_MILLIS) {
-                currentMin = currentMax;
-            }
+        protected long calculateDelayBound(long previousDelayBound) {
             // Exponential backoff calculation taken from: https://en.wikipedia.org/wiki/Exponential_backoff
             int uncappedBackoff = ((1 << Math.min(currentAttempt, MAX_RETRY_EXPONENT)) - 1) * (50);
             currentMax = Math.min(uncappedBackoff, MAX_RETRY_SLEEP_MILLIS);
-            // Its good to have a random window along the exponentially increasing curve
-            // so that not all bulk requests rest for the same amount of time
-            int randBound = (int)(1 + (currentMax - currentMin));
             String msg = new ParameterizedMessage(
                 "failed to {} after [{}] attempts. Will attempt again.",
                 getName(),
                 currentAttempt)
                 .getFormattedMessage();
             LOGGER.warn(() -> new ParameterizedMessage("[{}] {}", jobId, msg));
             msgHandler.accept(msg);
-            return randBound;
-        }
-
-        @Override
-        protected long minimumDelayMillis() {
-            return currentMin;
+            // RetryableAction randomizes in the interval [currentMax/2 ; currentMax].
+            // Its good to have a random window along the exponentially increasing curve
+            // so that not all bulk requests rest for the same amount of time
+            return currentMax;
         }
 
         @Override