SPARK-1999: StorageLevel in storage tab and RDD Storage Info never changes

StorageLevel in 'storage tab' and 'RDD Storage Info' never changes even if you call rdd.unpersist() and then you give the rdd another different storage level.

Author: CrazyJvm <crazyjvm@gmail.com>

Closes #968 from CrazyJvm/ui-storagelevel and squashes the following commits:

62555fa [CrazyJvm] change RDDInfo constructor param 'storageLevel' to var, so there's need to add another variable _storageLevel。
9f1571e [CrazyJvm] JIRA https://issues.apache.org/jira/browse/SPARK-1999 UI : StorageLevel in storage tab and RDD Storage Info never changes

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

@@ -26,7 +26,7 @@ class RDDInfo(
     val id: Int,
     val name: String,
     val numPartitions: Int,
-    val storageLevel: StorageLevel)
+    var storageLevel: StorageLevel)
   extends Ordered[RDDInfo] {
 
   var numCachedPartitions = 0
@@ -36,8 +36,8 @@ class RDDInfo(
 
   override def toString = {
     import Utils.bytesToString
-    ("RDD \"%s\" (%d) Storage: %s; CachedPartitions: %d; TotalPartitions: %d; MemorySize: %s; " +
-      "TachyonSize: %s; DiskSize: %s").format(
+    ("RDD \"%s\" (%d) StorageLevel: %s; CachedPartitions: %d; TotalPartitions: %d; " +
+      "MemorySize: %s; TachyonSize: %s; DiskSize: %s").format(
         name, id, storageLevel.toString, numCachedPartitions, numPartitions,
         bytesToString(memSize), bytesToString(tachyonSize), bytesToString(diskSize))
   }

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

@@ -89,10 +89,13 @@ private[spark] object StorageUtils {
       // Add up memory, disk and Tachyon sizes
       val persistedBlocks =
         blocks.filter { status => status.memSize + status.diskSize + status.tachyonSize > 0 }
+      val _storageLevel =
+        if (persistedBlocks.length > 0) persistedBlocks(0).storageLevel else StorageLevel.NONE
       val memSize = persistedBlocks.map(_.memSize).reduceOption(_ + _).getOrElse(0L)
       val diskSize = persistedBlocks.map(_.diskSize).reduceOption(_ + _).getOrElse(0L)
       val tachyonSize = persistedBlocks.map(_.tachyonSize).reduceOption(_ + _).getOrElse(0L)
       rddInfoMap.get(rddId).map { rddInfo =>
+        rddInfo.storageLevel = _storageLevel
         rddInfo.numCachedPartitions = persistedBlocks.length
         rddInfo.memSize = memSize
         rddInfo.diskSize = diskSize