Fix SPARK-4471: blockManagerIdFromJson function throws exception while B...

Fix [SPARK-4471](https://issues.apache.org/jira/browse/SPARK-4471): blockManagerIdFromJson function throws exception while BlockManagerId be null in MetadataFetchFailedException

Author: hushan[胡珊] <hushan@xiaomi.com>

Closes #3340 from suyanNone/fix-blockmanagerId-jnothing-2 and squashes the following commits:

159f9a3 [hushan[胡珊]] Refine test code for blockmanager is null
4380d73 [hushan[胡珊]] remove useless blank line
3ccf651 [hushan[胡珊]] Fix SPARK-4471: blockManagerIdFromJson function throws exception while metadata fetch failed

2 files changed, 16 insertions, 3 deletions

diff --git a/core/src/main/scala/org/apache/spark/util/JsonProtocol.scala b/core/src/main/scala/org/apache/spark/util/JsonProtocol.scala
index 7b5db1ed76..e7b80e8774 100644
--- a/core/src/main/scala/org/apache/spark/util/JsonProtocol.scala
+++ b/core/src/main/scala/org/apache/spark/util/JsonProtocol.scala
@@ -688,6 +688,10 @@ private[spark] object JsonProtocol {
   }
 
   def blockManagerIdFromJson(json: JValue): BlockManagerId = {
+    // On metadata fetch fail, block manager ID can be null (SPARK-4471)
+    if (json == JNothing) {
+      return null
+    }
     val executorId = (json \ "Executor ID").extract[String]
     val host = (json \ "Host").extract[String]
     val port = (json \ "Port").extract[Int]
diff --git a/core/src/test/scala/org/apache/spark/util/JsonProtocolSuite.scala b/core/src/test/scala/org/apache/spark/util/JsonProtocolSuite.scala
index 0bc9492675..593d6dd8c3 100644
--- a/core/src/test/scala/org/apache/spark/util/JsonProtocolSuite.scala
+++ b/core/src/test/scala/org/apache/spark/util/JsonProtocolSuite.scala
@@ -19,6 +19,8 @@ package org.apache.spark.util
 
 import java.util.Properties
 
+import org.apache.spark.shuffle.MetadataFetchFailedException
+
 import scala.collection.Map
 
 import org.json4s.jackson.JsonMethods._
@@ -116,10 +118,13 @@ class JsonProtocolSuite extends FunSuite {
     // TaskEndReason
     val fetchFailed = FetchFailed(BlockManagerId("With or", "without you", 15), 17, 18, 19,
       "Some exception")
+    val fetchMetadataFailed = new MetadataFetchFailedException(17,
+      19, "metadata Fetch failed exception").toTaskEndReason
     val exceptionFailure = new ExceptionFailure(exception, None)
     testTaskEndReason(Success)
     testTaskEndReason(Resubmitted)
     testTaskEndReason(fetchFailed)
+    testTaskEndReason(fetchMetadataFailed)
     testTaskEndReason(exceptionFailure)
     testTaskEndReason(TaskResultLost)
     testTaskEndReason(TaskKilled)
@@ -431,9 +436,13 @@ class JsonProtocolSuite extends FunSuite {
   }
 
   private def assertEquals(bm1: BlockManagerId, bm2: BlockManagerId) {
-    assert(bm1.executorId === bm2.executorId)
-    assert(bm1.host === bm2.host)
-    assert(bm1.port === bm2.port)
+    if (bm1 == null || bm2 == null) {
+      assert(bm1 === bm2)
+    } else {
+      assert(bm1.executorId === bm2.executorId)
+      assert(bm1.host === bm2.host)
+      assert(bm1.port === bm2.port)
+    }
   }
 
   private def assertEquals(result1: JobResult, result2: JobResult) {