Adding null condition to getRecords in the KinesisDataFetcher class. Changing the abstract class back to an interface.

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

@@ -1,13 +1,15 @@
 package com.amazonaws.services.kinesis.clientlibrary.lib.worker;
 
 import com.amazonaws.services.kinesis.model.GetRecordsResult;
+
 import lombok.extern.apachecommons.CommonsLog;
 
 /**
- *
+ * This is the BlockingGetRecordsCache class. This class blocks any calls to the getRecords on the
+ * GetRecordsRetrievalStrategy class.
  */
 @CommonsLog
-public class BlockingGetRecordsCache extends GetRecordsCache {
+public class BlockingGetRecordsCache implements GetRecordsCache {
     private final int maxRecordsPerCall;
     private final GetRecordsRetrievalStrategy getRecordsRetrievalStrategy;
 
@@ -18,7 +20,7 @@ public class BlockingGetRecordsCache extends GetRecordsCache {
     
     @Override
     public GetRecordsResult getNextResult() {
-        return validateGetRecordsResult(getRecordsRetrievalStrategy.getRecords(maxRecordsPerCall));
+        return getRecordsRetrievalStrategy.getRecords(maxRecordsPerCall);
     }
 
     @Override

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

@@ -7,21 +7,14 @@ import java.util.Collections;
 /**
  * This class is used as a cache for Prefetching data from Kinesis.
  */
-public abstract class GetRecordsCache {
+public interface GetRecordsCache {
     /**
      * This method returns the next set of records from the Cache if present, or blocks the request till it gets the
      * next set of records back from Kinesis.
      * 
      * @return The next set of records.
      */
-    public abstract GetRecordsResult getNextResult();
+    GetRecordsResult getNextResult();
     
-    public abstract void shutdown();
+    void shutdown();
-    
-    protected GetRecordsResult validateGetRecordsResult(final GetRecordsResult getRecordsResult) {
-        if (getRecordsResult == null) {
-            return new GetRecordsResult().withRecords(Collections.emptyList());
-        }
-        return getRecordsResult;
-    }
 }

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

@@ -14,18 +14,19 @@
  */
 package com.amazonaws.services.kinesis.clientlibrary.lib.worker;
 
+import java.util.Collections;
+import java.util.Date;
+
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
-import com.amazonaws.services.kinesis.model.GetRecordsResult;
-import com.amazonaws.services.kinesis.model.ResourceNotFoundException;
-import com.amazonaws.services.kinesis.model.ShardIteratorType;
 import com.amazonaws.services.kinesis.clientlibrary.lib.checkpoint.SentinelCheckpoint;
 import com.amazonaws.services.kinesis.clientlibrary.proxies.IKinesisProxy;
 import com.amazonaws.services.kinesis.clientlibrary.proxies.MetricsCollectingKinesisProxyDecorator;
 import com.amazonaws.services.kinesis.clientlibrary.types.ExtendedSequenceNumber;
-
+import com.amazonaws.services.kinesis.model.GetRecordsResult;
-import java.util.Date;
+import com.amazonaws.services.kinesis.model.ResourceNotFoundException;
+import com.amazonaws.services.kinesis.model.ShardIteratorType;
 
 /**
  * Used to get data from Amazon Kinesis. Tracks iterator state internally.
@@ -77,6 +78,10 @@ class KinesisDataFetcher {
         } else {
             isShardEndReached = true;
         }
+        
+        if (response == null) {
+            response = new GetRecordsResult().withRecords(Collections.emptyList());
+        }
 
         return response;
     }

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

@@ -1,8 +1,6 @@
 package com.amazonaws.services.kinesis.clientlibrary.lib.worker;
 
-import java.util.Collections;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
 import java.util.concurrent.LinkedBlockingQueue;
 
 import com.amazonaws.services.kinesis.model.GetRecordsResult;
@@ -16,11 +14,10 @@ import lombok.extern.apachecommons.CommonsLog;
  * number of GetRecordsResult that the cache can store, maxByteSize i.e. the byte size of the records stored in the
  * cache and maxRecordsCount i.e. the max number of records that should be present in the cache across multiple
  * GetRecordsResult object. If no data is available in the cache, the call from the record processor is blocked till
- * records are retrieved from Kinesis. If prefetching is not enabled, the cache is not used and every single call to the
+ * records are retrieved from Kinesis.
- * GetRecordsRetrievalStrategy is a blocking call.
  */
 @CommonsLog
-public class PrefetchGetRecordsCache extends GetRecordsCache {
+public class PrefetchGetRecordsCache implements GetRecordsCache {
     private LinkedBlockingQueue<GetRecordsResult> getRecordsResultQueue;
     private int maxSize;
     private int maxByteSize;
@@ -102,8 +99,7 @@ public class PrefetchGetRecordsCache extends GetRecordsCache {
             while (true) {
                 if (currentSizeInBytes < maxByteSize && currentRecordsCount < maxRecordsCount) {
                     try {
-                        GetRecordsResult getRecordsResult = validateGetRecordsResult(
+                        GetRecordsResult getRecordsResult = getRecordsRetrievalStrategy.getRecords(maxRecordsPerCall);
-                                getRecordsRetrievalStrategy.getRecords(maxRecordsPerCall));
                         getRecordsResultQueue.put(getRecordsResult);
                         if (getRecordsResultQueue.contains(getRecordsResult)) {
                             updateBytes(getRecordsResult, true);