Address some comments

external/kafka/src/main/scala/org/apache/spark/streaming/kafka/ReliableKafkaReceiver.scala

@@ -83,7 +83,7 @@ class ReliableKafkaReceiver[
    */
   private var blockGenerator: BlockGenerator = null
 
-  /** Threadpool running the handlers for receiving message from multiple topics and partitions. */
+  /** Thread pool running the handlers for receiving message from multiple topics and partitions. */
   private var messageHandlerThreadPool: ThreadPoolExecutor = null
 
   override def onStart(): Unit = {
@@ -142,7 +142,6 @@ class ReliableKafkaReceiver[
         messageHandlerThreadPool.submit(new MessageHandler(stream))
       }
     }
-    println("Starting")
   }
 
   override def onStop(): Unit = {
@@ -177,25 +176,28 @@ class ReliableKafkaReceiver[
     }
   }
 
-  /** Store a Kafka message and the associated metadata as a tuple */
+  /** Store a Kafka message and the associated metadata as a tuple. */
   private def storeMessageAndMetadata(
       msgAndMetadata: MessageAndMetadata[K, V]): Unit = synchronized {
     val topicAndPartition = TopicAndPartition(msgAndMetadata.topic, msgAndMetadata.partition)
     blockGenerator += ((msgAndMetadata.key, msgAndMetadata.message))
     topicPartitionOffsetMap.put(topicAndPartition, msgAndMetadata.offset)
   }
 
-  /** Remember the current offsets for each topic and partition. This is called when a block is generated */
+  /**
+   * Remember the current offsets for each topic and partition. This is called when a block is
+   * generated.
+   */
   private def rememberBlockOffsets(blockId: StreamBlockId): Unit = synchronized {
-    // Get a snapshot of current offset map and store with related block id. Since this hook
-    // function is called in synchronized block, so we can get the snapshot without explicit lock.
+    // Get a snapshot of current offset map and store with related block id.
     val offsetSnapshot = topicPartitionOffsetMap.toMap
     blockOffsetMap.put(blockId, offsetSnapshot)
     topicPartitionOffsetMap.clear()
   }
 
-  /** Store the ready-to-be-stored block and commit the related offsets to zookeeper */
-  private def storeBlockAndCommitOffset(blockId: StreamBlockId, arrayBuffer: mutable.ArrayBuffer[_]): Unit = {
+  /** Store the ready-to-be-stored block and commit the related offsets to zookeeper. */
+  private def storeBlockAndCommitOffset(
+      blockId: StreamBlockId, arrayBuffer: mutable.ArrayBuffer[_]): Unit = {
     store(arrayBuffer.asInstanceOf[mutable.ArrayBuffer[(K, V)]])
     Option(blockOffsetMap.get(blockId)).foreach(commitOffset)
     blockOffsetMap.remove(blockId)
@@ -232,7 +234,6 @@ class ReliableKafkaReceiver[
   private final class MessageHandler(stream: KafkaStream[K, V]) extends Runnable {
     override def run(): Unit = {
       while (!isStopped) {
-        println(s"Starting message process thread ${Thread.currentThread().getId}.")
         try {
           val streamIterator = stream.iterator()
           while (streamIterator.hasNext) {

external/kafka/src/test/java/org/apache/spark/streaming/kafka/JavaKafkaStreamSuite.java

@@ -33,8 +33,6 @@
 import org.apache.spark.api.java.JavaPairRDD;
 import org.apache.spark.api.java.function.Function;
 import org.apache.spark.storage.StorageLevel;
-import org.apache.spark.streaming.Duration;
-import org.apache.spark.streaming.LocalJavaStreamingContext;
 import org.apache.spark.streaming.api.java.JavaDStream;
 import org.apache.spark.streaming.api.java.JavaPairDStream;
 import org.apache.spark.streaming.api.java.JavaStreamingContext;
@@ -43,23 +41,25 @@
 import org.junit.After;
 import org.junit.Before;
 
-public class JavaKafkaStreamSuite extends KafkaStreamSuiteBase implements Serializable {
-    private transient JavaStreamingContext ssc = null;
-    private Random random = new Random();
+public class JavaKafkaStreamSuite implements Serializable {
+  private transient JavaStreamingContext ssc = null;
+  private Random random = new Random();
+  private transient KafkaStreamSuiteBase suiteBase = null;
 
   @Before
   public void setUp() {
-    beforeFunction();
+    suiteBase = new KafkaStreamSuiteBase() { };
+    suiteBase.beforeFunction();
     System.clearProperty("spark.driver.port");
-    ssc = new JavaStreamingContext(sparkConf(), batchDuration());
+    ssc = new JavaStreamingContext(suiteBase.sparkConf(), suiteBase.batchDuration());
   }
 
   @After
   public void tearDown() {
     ssc.stop();
     ssc = null;
     System.clearProperty("spark.driver.port");
-    afterFunction();
+    suiteBase.afterFunction();
   }
 
   @Test
@@ -73,14 +73,14 @@ public void testKafkaStream() throws InterruptedException {
     sent.put("b", 3);
     sent.put("c", 10);
 
-    createTopic(topic);
+    suiteBase.createTopic(topic);
     HashMap<String, Object> tmp = new HashMap<String, Object>(sent);
-    produceAndSendMessage(topic,
+    suiteBase.produceAndSendMessage(topic,
       JavaConverters.mapAsScalaMapConverter(tmp).asScala().toMap(
         Predef.<Tuple2<String, Object>>conforms()));
 
     HashMap<String, String> kafkaParams = new HashMap<String, String>();
-    kafkaParams.put("zookeeper.connect", zkAddress());
+    kafkaParams.put("zookeeper.connect", suiteBase.zkAddress());
     kafkaParams.put("group.id", "test-consumer-" + random.nextInt(10000));
     kafkaParams.put("auto.offset.reset", "smallest");
 

external/kafka/src/test/scala/org/apache/spark/streaming/kafka/KafkaStreamSuite.scala

@@ -42,7 +42,7 @@ import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.{Milliseconds, StreamingContext}
 import org.apache.spark.util.Utils
 
-abstract class KafkaStreamSuiteBase extends FunSuite with BeforeAndAfter with Logging {
+abstract class KafkaStreamSuiteBase extends FunSuite with Logging {
   import KafkaTestUtils._
 
   val sparkConf = new SparkConf()
@@ -154,7 +154,7 @@ abstract class KafkaStreamSuiteBase extends FunSuite with BeforeAndAfter with Lo
   }
 }
 
-class KafkaStreamSuite extends KafkaStreamSuiteBase with Eventually {
+class KafkaStreamSuite extends KafkaStreamSuiteBase with BeforeAndAfter with Eventually {
 
   before { beforeFunction() }
   after { afterFunction() }

external/kafka/src/test/scala/org/apache/spark/streaming/kafka/ReliableKafkaStreamSuite.scala

@@ -26,13 +26,14 @@ import scala.util.Random
 
 import kafka.serializer.StringDecoder
 import kafka.utils.{ZKGroupTopicDirs, ZkUtils}
+import org.scalatest.BeforeAndAfter
 import org.scalatest.concurrent.Eventually
 
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.StreamingContext
 import org.apache.spark.util.Utils
 
-class ReliableKafkaStreamSuite extends KafkaStreamSuiteBase with Eventually {
+class ReliableKafkaStreamSuite extends KafkaStreamSuiteBase with BeforeAndAfter with Eventually {
   val topic = "topic"
   val data = Map("a" -> 10, "b" -> 10, "c" -> 10)
   var groupId: String = _
@@ -85,7 +86,6 @@ class ReliableKafkaStreamSuite extends KafkaStreamSuiteBase with Eventually {
     }
     ssc.stop()
   }
-/*
   test("Verify the offset commit") {
     // Verify the correctness of offset commit mechanism.
     sparkConf.set("spark.streaming.receiver.writeAheadLog.enable", "true")
@@ -147,7 +147,7 @@ class ReliableKafkaStreamSuite extends KafkaStreamSuiteBase with Eventually {
     }
     ssc.stop()
   }
-*/
+
   /** Getting partition offset from Zookeeper. */
   private def getCommitOffset(groupId: String, topic: String, partition: Int): Long = {
     assert(zkClient != null, "Zookeeper client is not initialized")