From 4ba0febd580da7c17b2d3dc82439be41e67af2c8 Mon Sep 17 00:00:00 2001
From: Zhihai Xu <zxu@apache.org>
Date: Thu, 24 Sep 2015 11:48:11 -0700
Subject: [PATCH] HADOOP-12252. LocalDirAllocator should not throw NPE with
 empty string configuration. Contributed by Zhihai Xu

(cherry picked from commit 52c1f272ecb6c29c81898a1ff50d03a1296df1f7)

Conflicts:
	hadoop-common-project/hadoop-common/CHANGES.txt
---
 .../hadoop-common/CHANGES.txt                 |  3 +++
 .../apache/hadoop/fs/LocalDirAllocator.java   |  4 +--
 .../hadoop/fs/TestLocalDirAllocator.java      | 26 ++++++++++++++++++-
 3 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index 53311b9adaf..513d377835c 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -579,6 +579,9 @@ Release 2.8.0 - UNRELEASED
     required context item is not configured
     (Brahma Reddy Battula via harsh)
 
+    HADOOP-12252. LocalDirAllocator should not throw NPE with empty string
+    configuration. (Zhihai Xu)
+
   OPTIMIZATIONS
 
     HADOOP-12051. ProtobufRpcEngine.invoke() should use Exception.toString()
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/LocalDirAllocator.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/LocalDirAllocator.java
index 8f011ce409f..ccea6e5a2be 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/LocalDirAllocator.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/LocalDirAllocator.java
@@ -250,9 +250,9 @@ private static class AllocatorPerContext {
     private int dirNumLastAccessed;
     private Random dirIndexRandomizer = new Random();
     private FileSystem localFS;
-    private DF[] dirDF;
+    private DF[] dirDF = new DF[0];
     private String contextCfgItemName;
-    private String[] localDirs;
+    private String[] localDirs = new String[0];
     private String savedLocalDirs = "";
 
     public AllocatorPerContext(String contextCfgItemName) {
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestLocalDirAllocator.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestLocalDirAllocator.java
index 624fa14497e..5f56f9a0fb6 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestLocalDirAllocator.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestLocalDirAllocator.java
@@ -26,6 +26,7 @@
 import java.util.NoSuchElementException;
 
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.util.DiskChecker.DiskErrorException;
 import org.apache.hadoop.util.Shell;
 
 import org.junit.runner.RunWith;
@@ -312,7 +313,30 @@ public void testShouldNotthrowNPE() throws Exception {
     } catch (IOException e) {
       assertEquals(CONTEXT + " not configured", e.getMessage());
     } catch (NullPointerException e) {
-      fail("Lack of configuration should not have thrown an NPE.");
+      fail("Lack of configuration should not have thrown a NPE.");
+    }
+
+    String  NEW_CONTEXT = CONTEXT + ".new";
+    conf1.set(NEW_CONTEXT, "");
+    LocalDirAllocator newDirAllocator = new LocalDirAllocator(NEW_CONTEXT);
+    try {
+      newDirAllocator.getLocalPathForWrite("/test", conf1);
+      fail("Exception not thrown when " + NEW_CONTEXT +
+          " is set to empty string");
+    } catch (IOException e) {
+      assertTrue(e instanceof DiskErrorException);
+    } catch (NullPointerException e) {
+      fail("Wrong configuration should not have thrown a NPE.");
+    }
+
+    try {
+      newDirAllocator.getLocalPathToRead("/test", conf1);
+      fail("Exception not thrown when " + NEW_CONTEXT +
+          " is set to empty string");
+    } catch (IOException e) {
+      assertTrue(e instanceof DiskErrorException);
+    } catch (NullPointerException e) {
+      fail("Wrong configuration should not have thrown a NPE.");
     }
   }