Addressed PR comments

src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/ShutdownTask.java

@@ -15,6 +15,7 @@
 package com.amazonaws.services.kinesis.clientlibrary.lib.worker;
 
 import com.amazonaws.services.kinesis.clientlibrary.proxies.ShardClosureVerificationResponse;
+import com.amazonaws.services.kinesis.clientlibrary.proxies.ShardListWrappingShardClosureVerificationResponse;
 import com.amazonaws.services.kinesis.model.Shard;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -105,12 +106,13 @@ class ShutdownTask implements ITask {
              */
             if(localReason == ShutdownReason.TERMINATE) {
                 ShardClosureVerificationResponse shardClosureVerificationResponse = kinesisProxy.verifyShardClosure(shardInfo.getShardId());
-                latestShards = shardClosureVerificationResponse.getLatestShards();
+                if (shardClosureVerificationResponse instanceof ShardListWrappingShardClosureVerificationResponse) {
+                    latestShards = ((ShardListWrappingShardClosureVerificationResponse)shardClosureVerificationResponse).getLatestShards();
+                }
 
-                // If latestShards is null or empty, it means shard in context is not closed yet.
+                // If shard in context is not closed yet we should shut down the ShardConsumer with Zombie state
-                // We should shut down the ShardConsumer with Zombie state which avoids checkpoint-ing
+                // which avoids checkpoint-ing with SHARD_END sequence number.
-                // with SHARD_END sequence number.
+                if(!shardClosureVerificationResponse.isShardClosed()) {
-                if(!shardClosureVerificationResponse.isVerifiedShardWasClosed()) {
                     localReason = ShutdownReason.ZOMBIE;
                     dropLease();
                     LOG.info("Forcing the lease to be lost before shutting down the consumer for Shard: " + shardInfo.getShardId());

src/main/java/com/amazonaws/services/kinesis/clientlibrary/proxies/IKinesisProxy.java

@@ -17,7 +17,6 @@ package com.amazonaws.services.kinesis.clientlibrary.proxies;
 import java.nio.ByteBuffer;
 import java.util.Date;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
 
 import com.amazonaws.services.kinesis.model.DescribeStreamResult;
@@ -81,15 +80,10 @@ public interface IKinesisProxy {
 
     /**
      * Used to verify during ShardConsumer shutdown if the provided shardId is for a shard that has been closed.
-     * Returns the list of shards so it can be used for lease creation (instead of calling getShardList() again)
-     * along with the result of verification.
-     * Note that DynamoDBStreamsProxy does not implement this check and hence resorts to the default response.
      * @param shardId Id of the shard that needs to be verified.
      * @return an Object of type ShardClosureVerificationResponse.
      */
-    default ShardClosureVerificationResponse verifyShardClosure(String shardId) {
+    ShardClosureVerificationResponse verifyShardClosure(String shardId);
-        return new ShardClosureVerificationResponse(true /*isVerifiedShardWasClosed*/, null /*latestShards*/);
-    }
 
     /**
      * Fetch a shard iterator from the specified position in the shard.

src/main/java/com/amazonaws/services/kinesis/clientlibrary/proxies/KinesisProxy.java

@@ -479,29 +479,29 @@ public class KinesisProxy implements IKinesisProxyExtended {
 
     /**
      * Used to verify during ShardConsumer shutdown if the provided shardId is for a shard that has been closed.
-     * Returns the list of shards so it can be used for lease creation (instead of calling getShardList() again)
+     * Also returns the list of shards wrapped in the response so that it can be used for lease creation
-     * along with the result of verification.
+     * (instead of calling getShardList() again).
      * @param shardId Id of the shard that needs to be verified.
      * @return an Object of type ShardClosureVerificationResponse.
      */
     @Override public ShardClosureVerificationResponse verifyShardClosure(String shardId) {
         List<Shard> shards = this.getShardList();
         if (!CollectionUtils.isNullOrEmpty(shards) && isShardParentOfAny(shardId, shards)) {
-            return new ShardClosureVerificationResponse(true /*isVerifiedShardWasClosed*/, shards /*latestShards*/);
+            return new ShardListWrappingShardClosureVerificationResponse(true /*isVerifiedShardWasClosed*/, shards /*latestShards*/);
         }
-        return new ShardClosureVerificationResponse(false /*isVerifiedShardWasClosed*/, shards /*latestShards*/);
+        return new ShardListWrappingShardClosureVerificationResponse(false /*isVerifiedShardWasClosed*/, shards /*latestShards*/);
     }
 
     private boolean isShardParentOfAny(String shardId, List<Shard> shards) {
         for(Shard shard : shards) {
-            if (isChildShardOfShard(shard, shardId)) {
+            if (isShardAParent(shard, shardId)) {
                 return true;
             }
         }
         return false;
     }
 
-    private boolean isChildShardOfShard(Shard shard, String shardId) {
+    private boolean isShardAParent(Shard shard, String shardId) {
         return (StringUtils.equals(shard.getParentShardId(), shardId)
                 || StringUtils.equals(shard.getAdjacentParentShardId(), shardId));
     }

src/main/java/com/amazonaws/services/kinesis/clientlibrary/proxies/MetricsCollectingKinesisProxyDecorator.java

@@ -180,8 +180,7 @@ public class MetricsCollectingKinesisProxyDecorator implements IKinesisProxy {
     }
 
     /**
-     * @param shardId Id of the shard that needs to be verified.
+     * {@inheritDoc}
-     * @return
      */
     @Override public ShardClosureVerificationResponse verifyShardClosure(String shardId) {
         return other.verifyShardClosure(shardId);

src/main/java/com/amazonaws/services/kinesis/clientlibrary/proxies/ShardClosureVerificationResponse.java

@@ -1,27 +1,13 @@
 package com.amazonaws.services.kinesis.clientlibrary.proxies;
 
-import com.amazonaws.services.kinesis.model.Shard;
-import lombok.Getter;
-
-import java.util.List;
-
 /**
  * ShutDown task verifies if the shard in context is necessarily closed before checkpointing the shard at SHARD_END.
- * The verification is done by IKinesisProxy and this class is used to wrap the verification results.
+ * The verification is done by IKinesisProxy and implementations of this interface are used to wrap the verification results.
  */
-@Getter
+public interface ShardClosureVerificationResponse {
-public class ShardClosureVerificationResponse {
-
-    private final boolean verifiedShardWasClosed;
-    private final List<Shard> latestShards;
 
     /**
-     * Used to capture response from KinesisProxy.verifyShardClosure method.
+     * @return A boolean value indicating whether or not the shard in context (for which the request was made) is closed.
-     * @param verifiedShardWasClosed If the provided shardId corresponds to a shard that was verified as closed.
-     * @param latestShards Result returned by KinesisProxy.getShardList() used for verification.
      */
-    public ShardClosureVerificationResponse(boolean verifiedShardWasClosed, List<Shard> latestShards) {
+    boolean isShardClosed();
-        this.verifiedShardWasClosed = verifiedShardWasClosed;
-        this.latestShards = latestShards;
-    }
 }

src/main/java/com/amazonaws/services/kinesis/clientlibrary/proxies/ShardListWrappingShardClosureVerificationResponse.java

@@ -0,0 +1,32 @@
+package com.amazonaws.services.kinesis.clientlibrary.proxies;
+
+import com.amazonaws.services.kinesis.model.Shard;
+import lombok.Getter;
+
+import java.util.List;
+
+/**
+ * Implementation of ShardClosureVerificationResponse that also wraps the latest results
+ * from IKinesisProxy.getShardList() in it.
+ */
+public class ShardListWrappingShardClosureVerificationResponse implements ShardClosureVerificationResponse {
+
+    private final boolean isShardClosed;
+
+    @Getter
+    private final List<Shard> latestShards;
+
+    /**
+     * Used to capture response from KinesisProxy.verifyShardClosure method.
+     * @param isShardClosed If the provided shardId corresponds to a shard that was verified as closed.
+     * @param latestShards Result returned by KinesisProxy.getShardList() used for verification.
+     */
+    public ShardListWrappingShardClosureVerificationResponse(boolean isShardClosed, List<Shard> latestShards) {
+        this.isShardClosed = isShardClosed;
+        this.latestShards = latestShards;
+    }
+
+    @Override public boolean isShardClosed() {
+        return isShardClosed;
+    }
+}

src/test/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/ShutdownTaskTest.java

@@ -28,7 +28,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 
-import com.amazonaws.services.kinesis.clientlibrary.proxies.ShardClosureVerificationResponse;
+import com.amazonaws.services.kinesis.clientlibrary.proxies.ShardListWrappingShardClosureVerificationResponse;
 import com.amazonaws.services.kinesis.model.HashKeyRange;
 import com.amazonaws.services.kinesis.model.SequenceNumberRange;
 import com.amazonaws.services.kinesis.model.Shard;
@@ -114,7 +114,7 @@ public class ShutdownTaskTest {
         IKinesisProxy kinesisProxy = mock(IKinesisProxy.class);
         List<Shard> shards = constructShardListForGraphA();
         when(kinesisProxy.getShardList()).thenReturn(shards);
-        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardClosureVerificationResponse(true, shards));
+        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardListWrappingShardClosureVerificationResponse(true, shards));
         KinesisClientLibLeaseCoordinator leaseCoordinator = mock(KinesisClientLibLeaseCoordinator.class);
         ILeaseManager<KinesisClientLease> leaseManager = mock(KinesisClientLeaseManager.class);
         when(leaseCoordinator.getLeaseManager()).thenReturn(leaseManager);
@@ -148,7 +148,7 @@ public class ShutdownTaskTest {
         List<Shard> shards = constructShardListForGraphA();
         IKinesisProxy kinesisProxy = mock(IKinesisProxy.class);
         when(kinesisProxy.getShardList()).thenReturn(shards);
-        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardClosureVerificationResponse(true, shards));
+        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardListWrappingShardClosureVerificationResponse(true, shards));
         KinesisClientLibLeaseCoordinator leaseCoordinator = mock(KinesisClientLibLeaseCoordinator.class);
         ILeaseManager<KinesisClientLease> leaseManager = mock(KinesisClientLeaseManager.class);
         when(leaseCoordinator.getLeaseManager()).thenReturn(leaseManager);
@@ -184,7 +184,7 @@ public class ShutdownTaskTest {
         List<Shard> shards = constructShardListForGraphA();
         IKinesisProxy kinesisProxy = mock(IKinesisProxy.class);
         when(kinesisProxy.getShardList()).thenReturn(shards);
-        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardClosureVerificationResponse(true, shards));
+        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardListWrappingShardClosureVerificationResponse(true, shards));
         KinesisClientLibLeaseCoordinator leaseCoordinator = mock(KinesisClientLibLeaseCoordinator.class);
         ILeaseManager<KinesisClientLease> leaseManager = mock(KinesisClientLeaseManager.class);
         when(leaseCoordinator.getLeaseManager()).thenReturn(leaseManager);
@@ -225,7 +225,7 @@ public class ShutdownTaskTest {
         List<Shard> shards = constructShardListForGraphA();
         IKinesisProxy kinesisProxy = mock(IKinesisProxy.class);
         when(kinesisProxy.getShardList()).thenReturn(shards);
-        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardClosureVerificationResponse(false, shards));
+        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardListWrappingShardClosureVerificationResponse(false, shards));
         KinesisClientLibLeaseCoordinator leaseCoordinator = mock(KinesisClientLibLeaseCoordinator.class);
         ILeaseManager<KinesisClientLease> leaseManager = mock(KinesisClientLeaseManager.class);
         when(leaseCoordinator.getLeaseManager()).thenReturn(leaseManager);
@@ -263,7 +263,7 @@ public class ShutdownTaskTest {
         List<Shard> shards = constructShardListForGraphA();
         IKinesisProxy kinesisProxy = mock(IKinesisProxy.class);
         when(kinesisProxy.getShardList()).thenReturn(shards);
-        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardClosureVerificationResponse(false, shards));
+        when(kinesisProxy.verifyShardClosure(anyString())).thenReturn(new ShardListWrappingShardClosureVerificationResponse(false, shards));
         KinesisClientLibLeaseCoordinator leaseCoordinator = mock(KinesisClientLibLeaseCoordinator.class);
         ILeaseManager<KinesisClientLease> leaseManager = mock(KinesisClientLeaseManager.class);
         when(leaseCoordinator.getLeaseManager()).thenReturn(leaseManager);

src/test/java/com/amazonaws/services/kinesis/clientlibrary/proxies/KinesisLocalFileProxy.java

@@ -428,24 +428,24 @@ public class KinesisLocalFileProxy implements IKinesisProxy {
     /**
      * {@inheritDoc}
      */
-    @Override public ShardClosureVerificationResponse verifyShardClosure(String shardId) {
+    @Override public ShardListWrappingShardClosureVerificationResponse verifyShardClosure(String shardId) {
         List<Shard> shards = this.getShardList();
         if (!CollectionUtils.isNullOrEmpty(shards) && isShardParentOfAny(shardId, shards)) {
-            return new ShardClosureVerificationResponse(true /*isVerifiedShardWasClosed*/, shards /*latestShards*/);
+            return new ShardListWrappingShardClosureVerificationResponse(true /*isVerifiedShardWasClosed*/, shards /*latestShards*/);
         }
-        return new ShardClosureVerificationResponse(false /*isVerifiedShardWasClosed*/, shards /*latestShards*/);
+        return new ShardListWrappingShardClosureVerificationResponse(false /*isVerifiedShardWasClosed*/, shards /*latestShards*/);
     }
 
     private boolean isShardParentOfAny(String shardId, List<Shard> shards) {
         for(Shard shard : shards) {
-            if (isChildShardOfShard(shard, shardId)) {
+            if (isShardAParent(shard, shardId)) {
                 return true;
             }
         }
         return false;
     }
 
-    private boolean isChildShardOfShard(Shard shard, String shardId) {
+    private boolean isShardAParent(Shard shard, String shardId) {
         return (StringUtils.equals(shard.getParentShardId(), shardId)
                 || StringUtils.equals(shard.getAdjacentParentShardId(), shardId));
     }