Adding option to force sync to the filesystem

core/src/main/scala/org/apache/spark/storage/DiskStore.scala

@@ -63,17 +63,20 @@ private class DiskStore(blockManager: BlockManager, rootDirs: String)
     }
 
     private val f: File = createFile(blockId /*, allowAppendExisting */)
+    private val syncWrites = System.getProperty("spark.shuffle.sync", "false").toBoolean
 
     // The file channel, used for repositioning / truncating the file.
     private var channel: FileChannel = null
     private var bs: OutputStream = null
+    private var fos: FileOutputStream = null
     private var ts: TimeTrackingOutputStream = null
     private var objOut: SerializationStream = null
     private var lastValidPosition = 0L
     private var initialized = false
+    private var syncTime = 0L
 
     override def open(): DiskBlockObjectWriter = {
-      val fos = new FileOutputStream(f, true)
+      fos = new FileOutputStream(f, true)
       ts = new TimeTrackingOutputStream(fos)
       channel = fos.getChannel()
       bs = blockManager.wrapForCompression(blockId, new FastBufferedOutputStream(ts, bufferSize))
@@ -84,9 +87,19 @@ private class DiskStore(blockManager: BlockManager, rootDirs: String)
 
     override def close() {
       if (initialized) {
+        if (syncWrites) {
+          val start = System.nanoTime()
+          objOut.flush()
+          fos.getFD.sync()
           objOut.close()
+          syncTime += System.nanoTime() - start
+        } else {
+          objOut.close()
+        }
+
         channel = null
         bs = null
+        fos = null
         ts = null
         objOut = null
       }
@@ -132,7 +145,8 @@ private class DiskStore(blockManager: BlockManager, rootDirs: String)
     override def size(): Long = lastValidPosition
 
     override def timeWriting: Long = {
-      Option(ts).map(t => t.timeWriting).getOrElse(0L) // ts could be null if never written to
+      // ts could be null if never written to
+      Option(ts).map(t => t.timeWriting).getOrElse(0L) + syncTime
     }
   }