Hash range hole confidence check

amazon-kinesis-client/src/main/java/software/amazon/kinesis/coordinator/PeriodicShardSyncManager.java

@@ -17,6 +17,7 @@ package software.amazon.kinesis.coordinator;
 import com.google.common.annotations.VisibleForTesting;
 import lombok.EqualsAndHashCode;
 import lombok.Getter;
+import lombok.NonNull;
 import lombok.Value;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang3.Validate;
@@ -61,6 +62,8 @@ class PeriodicShardSyncManager {
     private static final long PERIODIC_SHARD_SYNC_INTERVAL_MILLIS = 5 * 60 * 1000L;
     private static final BigInteger MIN_HASH_KEY = BigInteger.ZERO;
     private static final BigInteger MAX_HASH_KEY = new BigInteger("2").pow(128).subtract(BigInteger.ONE);
+    private static final int CONSECUTIVE_HOLES_FOR_TRIGGERING_RECOVERY = 3;
+    private Map<StreamIdentifier, HashRangeHoleTracker> hashRangeHoleTrackerMap = new HashMap<>();
 
     private final String workerId;
     private final LeaderDecider leaderDecider;
@@ -145,6 +148,7 @@ class PeriodicShardSyncManager {
             try {
                 final Map<StreamIdentifier, List<Lease>> streamToLeasesMap = getStreamToLeasesMap(currentStreamConfigMap.keySet());
                 for (Map.Entry<StreamIdentifier, StreamConfig> streamConfigEntry : currentStreamConfigMap.entrySet()) {
+
                     final ShardSyncTaskManager shardSyncTaskManager = shardSyncTaskManagerProvider.apply(streamConfigEntry.getValue());
                     if (!shardSyncTaskManager.syncShardAndLeaseInfo()) {
                         log.warn(
@@ -160,7 +164,8 @@ class PeriodicShardSyncManager {
         }
     }
 
-    private Map<StreamIdentifier, List<Lease>> getStreamToLeasesMap(final Set<StreamIdentifier> streamIdentifiersToFilter)
+    private Map<StreamIdentifier, List<Lease>> getStreamToLeasesMap(
+            final Set<StreamIdentifier> streamIdentifiersToFilter)
             throws DependencyException, ProvisionedThroughputException, InvalidStateException {
         final List<Lease> leases = leaseRefresher.listLeases();
         if (!isMultiStreamingMode) {
@@ -179,25 +184,37 @@ class PeriodicShardSyncManager {
         }
     }
 
-    /**
+    // TODO : Catch exception
-     * Checks if the entire hash range is covered
+    private boolean shouldDoShardSync(StreamIdentifier streamIdentifier, List<Lease> leases) {
-     * @return true if covered, false otherwise
-     */
-    private boolean isHashRangeCompleteForLeases(List<Lease> leases) {
         if (CollectionUtils.isNullOrEmpty(leases)) {
-            return false;
+            throw new IllegalArgumentException("No leases found to validate for the stream " + streamIdentifier);
+        }
+        // Check if there are any holes in the leases and return the first hole if present.
+        Optional<HashRangeHole> hashRangeHoleOpt = hasHoleInLeases(streamIdentifier, leases);
+        if (hashRangeHoleOpt.isPresent()) {
+            // If hole is present, check if the hole is detected consecutively in previous occurrences.
+            // If hole is determined with high confidence return true; return false otherwise
+            return hashRangeHoleTrackerMap.computeIfAbsent(streamIdentifier, s -> new HashRangeHoleTracker())
+                    .hasHighConfidenceOfHoleWith(hashRangeHoleOpt.get());
+
         } else {
-            List<HashKeyRangeForLease> hashRangesForActiveLeases = leases.stream()
+            // If hole is not present, clear any previous tracking for this stream and return false;
-                    .filter(lease -> lease.checkpoint() != null && !lease.checkpoint().isShardEnd())
+            hashRangeHoleTrackerMap.remove(streamIdentifier);
-                    .map(lease -> lease.hashKeyRangeForLease())
+            return false;
-                    .collect(Collectors.toList());
-            return !checkForHoleInHashKeyRanges(hashRangesForActiveLeases, MIN_HASH_KEY, MAX_HASH_KEY).isPresent();
         }
     }
 
+    private Optional<HashRangeHole> hasHoleInLeases(StreamIdentifier streamIdentifier, List<Lease> leases) {
+        // Filter the hashranges of leases which has any checkpoint other than shard end.
+        List<HashKeyRangeForLease> hashRangesForActiveLeases = leases.stream()
+                .filter(lease -> lease.checkpoint() != null && !lease.checkpoint().isShardEnd())
+                .map(lease -> lease.hashKeyRangeForLease()).collect(Collectors.toList());
+        return checkForHoleInHashKeyRanges(streamIdentifier, hashRangesForActiveLeases, MIN_HASH_KEY, MAX_HASH_KEY);
+    }
+
     @VisibleForTesting
-    static Optional<HashRangeHole> checkForHoleInHashKeyRanges(List<HashKeyRangeForLease> hashKeyRanges,
+    static Optional<HashRangeHole> checkForHoleInHashKeyRanges(StreamIdentifier streamIdentifier,
-            BigInteger minHashKey, BigInteger maxHashKey) {
+            List<HashKeyRangeForLease> hashKeyRanges, BigInteger minHashKey, BigInteger maxHashKey) {
         List<HashKeyRangeForLease> mergedHashKeyRanges = sortAndMergeOverlappingHashRanges(hashKeyRanges);
 
         if (!mergedHashKeyRanges.get(0).startingHashKey().equals(minHashKey) || !mergedHashKeyRanges
@@ -225,7 +242,8 @@ class PeriodicShardSyncManager {
     }
 
     @VisibleForTesting
-    static List<HashKeyRangeForLease> sortAndMergeOverlappingHashRanges(List<HashKeyRangeForLease> hashKeyRanges) {
+    static List<HashKeyRangeForLease> sortAndMergeOverlappingHashRanges(
+            List<HashKeyRangeForLease> hashKeyRanges) {
         if (hashKeyRanges.size() == 0 || hashKeyRanges.size() == 1)
             return hashKeyRanges;
 
@@ -257,6 +275,21 @@ class PeriodicShardSyncManager {
         private final HashKeyRangeForLease hashRangeAtEndOfPossibleHole;
     }
 
+    private static class HashRangeHoleTracker {
+        private HashRangeHole hashRangeHole;
+        private Integer numConsecutiveHoles;
+
+        public boolean hasHighConfidenceOfHoleWith(@NonNull HashRangeHole hashRangeHole) {
+            if (hashRangeHole.equals(this.hashRangeHole)) {
+                ++this.numConsecutiveHoles;
+            } else {
+                this.hashRangeHole = hashRangeHole;
+                this.numConsecutiveHoles = 1;
+            }
+            return numConsecutiveHoles >= CONSECUTIVE_HOLES_FOR_TRIGGERING_RECOVERY;
+        }
+    }
+
     /**
      * Helper class to compare leases based on their hash range.
      */
@@ -264,8 +297,7 @@ class PeriodicShardSyncManager {
 
         private static final long serialVersionUID = 1L;
 
-        @Override
+        @Override public int compare(HashKeyRangeForLease hashKeyRange, HashKeyRangeForLease otherHashKeyRange) {
-        public int compare(HashKeyRangeForLease hashKeyRange, HashKeyRangeForLease otherHashKeyRange) {
             return hashKeyRange.startingHashKey().compareTo(otherHashKeyRange.startingHashKey());
         }
     }