Minor changes based on PR comments.

Author: tdas

streaming/src/main/scala/org/apache/spark/streaming/util/HdfsUtils.scala

@@ -17,12 +17,11 @@
 package org.apache.spark.streaming.util
 
 import org.apache.hadoop.conf.Configuration
-import org.apache.hadoop.fs.{LocalFileSystem, FSDataInputStream, FSDataOutputStream, Path}
+import org.apache.hadoop.fs._
 
 private[streaming] object HdfsUtils {
 
   def getOutputStream(path: String, conf: Configuration): FSDataOutputStream = {
-    // HDFS is not thread-safe when getFileSystem is called, so synchronize on that
     val dfsPath = new Path(path)
     val dfs = getFileSystemForPath(dfsPath, conf)
     // If the file exists and we have append support, append instead of creating a new file
@@ -61,7 +60,9 @@ private[streaming] object HdfsUtils {
     blockLocs.map(_.flatMap(_.getHosts))
   }
 
-  def getFileSystemForPath(path: Path, conf: Configuration) = synchronized {
+  def getFileSystemForPath(path: Path, conf: Configuration): FileSystem = synchronized {
+    // For local file systems, return the raw loca file system, such calls to flush()
+    // actually flushes the stream.
     val fs = path.getFileSystem(conf)
     fs match {
       case localFs: LocalFileSystem => localFs.getRawFileSystem

streaming/src/main/scala/org/apache/spark/streaming/util/WriteAheadLogManager.scala

@@ -37,7 +37,7 @@ import WriteAheadLogManager._
  * Uses [[org.apache.spark.streaming.util.WriteAheadLogWriter]] to write
  * and [[org.apache.spark.streaming.util.WriteAheadLogReader]] to read.
  *
- *@param logDirectory Directory when rotating log files will be created.
+ * @param logDirectory Directory when rotating log files will be created.
  * @param hadoopConf Hadoop configuration for reading/writing log files.
  * @param rollingIntervalSecs The interval in seconds with which logs will be rolled over.
  *                            Default is one minute.
@@ -57,7 +57,7 @@ private[streaming] class WriteAheadLogManager(
 
   private val pastLogs = new ArrayBuffer[LogInfo]
   private val callerNameTag =
-    if (callerName != null && callerName.nonEmpty) s" for $callerName" else ""
+    if (callerName.nonEmpty) s" for $callerName" else ""
   private val threadpoolName = s"WriteAheadLogManager $callerNameTag"
   implicit private val executionContext = ExecutionContext.fromExecutorService(
     Utils.newDaemonFixedThreadPool(1, threadpoolName))