From f44b599003bb79b1ec9b92e7546546523ec01676 Mon Sep 17 00:00:00 2001
From: Jing Zhao <jing9@apache.org>
Date: Wed, 26 Aug 2015 16:26:18 -0700
Subject: [PATCH] HDFS-8896. DataNode object isn't GCed when shutdown, because
 it has GC root in ShutdownHookManager. Contributed by Walter Su.

---
 .../java/org/apache/hadoop/util/ShutdownHookManager.java    | 6 ++++++
 hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt                 | 3 +++
 .../test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java    | 2 ++
 3 files changed, 11 insertions(+)

diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ShutdownHookManager.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ShutdownHookManager.java
index 989c96a8e37..85533dbffae 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ShutdownHookManager.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ShutdownHookManager.java
@@ -187,4 +187,10 @@ public class ShutdownHookManager {
     return shutdownInProgress.get();
   }
 
+  /**
+   * clear all registered shutdownHooks.
+   */
+  public void clearShutdownHooks() {
+    hooks.clear();
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 607de79d093..54c2d219bd3 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -841,6 +841,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8951. Move the shortcircuit package to hdfs-client.
     (Mingliang Liu via wheat9)
 
+    HDFS-8896. DataNode object isn't GCed when shutdown, because it has GC
+    root in ShutdownHookManager. (Walter Su via jing9)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java
index 70523216831..24e0965b5fb 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java
@@ -119,6 +119,7 @@ import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.authorize.ProxyUsers;
 import org.apache.hadoop.test.GenericTestUtils;
 import org.apache.hadoop.util.ExitUtil;
+import org.apache.hadoop.util.ShutdownHookManager;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.ToolRunner;
 
@@ -1867,6 +1868,7 @@ public class MiniDFSCluster {
         nameNode = null;
       }
     }
+    ShutdownHookManager.get().clearShutdownHooks();
     if (base_dir != null) {
       if (deleteDfsDir) {
         base_dir.delete();