[spark] branch branch-2.4 updated: [SPARK-31422][CORE] Fix NPE when BlockManagerSource is used after BlockManagerMaster stops

[do...@apache.org]

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dongjoon pushed a commit to branch branch-2.4
in repository https://gitbox.apache.org/repos/asf/spark.git


The following commit(s) were added to refs/heads/branch-2.4 by this push:
     new 26d5e8f  [SPARK-31422][CORE] Fix NPE when BlockManagerSource is used after BlockManagerMaster stops
26d5e8f is described below

commit 26d5e8fb57e7bcf1ae862508ab5806b0aa9a1c3c
Author: Dongjoon Hyun <do...@apache.org>
AuthorDate: Sat Apr 11 08:27:30 2020 -0700

    [SPARK-31422][CORE] Fix NPE when BlockManagerSource is used after BlockManagerMaster stops
    
    ### What changes were proposed in this pull request?
    
    This PR (SPARK-31422) aims to return empty result in order to avoid `NullPointerException` at `getStorageStatus` and `getMemoryStatus` which happens after `BlockManagerMaster` stops. The empty result is consistent with the current status of `SparkContext` because `BlockManager` and `BlockManagerMaster` is already stopped.
    
    ### Why are the changes needed?
    
    In `SparkEnv.stop`, the following stop sequence is used and `metricsSystem.stop` invokes `sink.stop`.
    ```
    blockManager.master.stop()
    metricsSystem.stop() --> sinks.foreach(_.stop)
    ```
    
    However, some sink can invoke `BlockManagerSource` and ends up with `NullPointerException` because `BlockManagerMaster` is already stopped and `driverEndpoint` became `null`.
    ```
    java.lang.NullPointerException
    at org.apache.spark.storage.BlockManagerMaster.getStorageStatus(BlockManagerMaster.scala:170)
    at org.apache.spark.storage.BlockManagerSource$$anonfun$10.apply(BlockManagerSource.scala:63)
    at org.apache.spark.storage.BlockManagerSource$$anonfun$10.apply(BlockManagerSource.scala:63)
    at org.apache.spark.storage.BlockManagerSource$$anon$1.getValue(BlockManagerSource.scala:31)
    at org.apache.spark.storage.BlockManagerSource$$anon$1.getValue(BlockManagerSource.scala:30)
    ```
    
    Since `SparkContext` registers and forgets `BlockManagerSource` without deregistering, we had better avoid `NullPointerException` inside `BlockManagerMaster` preventively.
    ```scala
    _env.metricsSystem.registerSource(new BlockManagerSource(_env.blockManager))
    ```
    
    ### Does this PR introduce any user-facing change?
    
    Yes. This will remove NPE for the users who uses `BlockManagerSource`.
    
    ### How was this patch tested?
    
    Pass the Jenkins with the newly added test cases.
    
    Closes #28187 from dongjoon-hyun/SPARK-31422.
    
    Authored-by: Dongjoon Hyun <do...@apache.org>
    Signed-off-by: Dongjoon Hyun <do...@apache.org>
    (cherry picked from commit a6e6fbf2ca23e51d43f175907ce6f29c946e1acf)
    Signed-off-by: Dongjoon Hyun <do...@apache.org>
---
 .../apache/spark/storage/BlockManagerMaster.scala  |  2 ++
 .../spark/storage/BlockManagerMasterSuite.scala    | 35 ++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala b/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala
index d24421b..9883d54 100644
--- a/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala
+++ b/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala
@@ -163,10 +163,12 @@ class BlockManagerMaster(
    * amount of remaining memory.
    */
   def getMemoryStatus: Map[BlockManagerId, (Long, Long)] = {
+    if (driverEndpoint == null) return Map.empty
     driverEndpoint.askSync[Map[BlockManagerId, (Long, Long)]](GetMemoryStatus)
   }
 
   def getStorageStatus: Array[StorageStatus] = {
+    if (driverEndpoint == null) return Array.empty
     driverEndpoint.askSync[Array[StorageStatus]](GetStorageStatus)
   }
 
diff --git a/core/src/test/scala/org/apache/spark/storage/BlockManagerMasterSuite.scala b/core/src/test/scala/org/apache/spark/storage/BlockManagerMasterSuite.scala
new file mode 100644
index 0000000..0d54726
--- /dev/null
+++ b/core/src/test/scala/org/apache/spark/storage/BlockManagerMasterSuite.scala
@@ -0,0 +1,35 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.storage
+
+import org.junit.Assert.assertTrue
+
+import org.apache.spark.{SparkConf, SparkFunSuite}
+
+class BlockManagerMasterSuite extends SparkFunSuite {
+
+  test("SPARK-31422: getMemoryStatus should not fail after BlockManagerMaster stops") {
+    val bmm = new BlockManagerMaster(null, null, new SparkConf, true)
+    assertTrue(bmm.getMemoryStatus.isEmpty)
+  }
+
+  test("SPARK-31422: getStorageStatus should not fail after BlockManagerMaster stops") {
+    val bmm = new BlockManagerMaster(null, null, new SparkConf, true)
+    assertTrue(bmm.getStorageStatus.isEmpty)
+  }
+}


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