fixing autooffset.reset behavior when set to 'largest'

streaming/src/main/scala/spark/streaming/dstream/KafkaInputDStream.scala

@@ -75,9 +75,9 @@ class KafkaReceiver(kafkaParams: Map[String, String],
     consumerConnector = Consumer.create(consumerConfig)
     logInfo("Connected to " + kafkaParams("zk.connect"))
 
-    // When autooffset.reset is 'smallest', it is our responsibility to try and whack the
+    // When autooffset.reset is defined, it is our responsibility to try and whack the
     // consumer group zk node.
-    if (kafkaParams.get("autooffset.reset").exists(_ == "smallest")) {
+    if (kafkaParams.contains("autooffset.reset")) {
       tryZookeeperConsumerGroupCleanup(kafkaParams("zk.connect"), kafkaParams("groupid"))
     }
 
@@ -100,9 +100,11 @@ class KafkaReceiver(kafkaParams: Map[String, String],
     }
   }
 
-  // Delete consumer group from zookeeper. This effectivly resets the group so we can consume from the beginning again.
+  // It is our responsibility to delete the consumer group when specifying autooffset.reset. This is because
+  // Kafka 0.7.2 only honors this param when the group is not in zookeeper.
+  //
   // The kafka high level consumer doesn't expose setting offsets currently, this is a trick copied from Kafkas'
-  // ConsoleConsumer. See code related to 'autooffset.reset' when it is set to 'smallest':
+  // ConsoleConsumer. See code related to 'autooffset.reset' when it is set to 'smallest'/'largest':
   // https://github.com/apache/kafka/blob/0.7.2/core/src/main/scala/kafka/consumer/ConsoleConsumer.scala
   private def tryZookeeperConsumerGroupCleanup(zkUrl: String, groupId: String) {
     try {