From 1035f550b9019ed7fe6479dc37a4858aafa33d12 Mon Sep 17 00:00:00 2001
From: Tsuyoshi Ozawa <ozawa@apache.org>
Date: Mon, 4 May 2015 15:02:21 +0900
Subject: [PATCH] MAPREDUCE-5905. CountersStrings.toEscapedCompactStrings
 outputs unnecessary null strings. Contributed by Akira AJISAKA.

(cherry picked from commit 3ba18362f2a4b83635b89aa0adc5ebaf27d9ca83)
---
 hadoop-mapreduce-project/CHANGES.txt            |  3 +++
 .../hadoop/mapreduce/util/CountersStrings.java  | 17 ++---------------
 .../org/apache/hadoop/mapred/TestCounters.java  |  3 +++
 3 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index 963da70cd5c..84c5f854003 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -107,6 +107,9 @@ Release 2.8.0 - UNRELEASED
     MAPREDUCE-6345. Documentation fix for when CRLA is enabled for MRAppMaster
     logs. (Rohit Agarwal via gera)
 
+    MAPREDUCE-5905. CountersStrings.toEscapedCompactStrings outputs
+    unnecessary "null" strings. (Akira AJISAKA via ozawa)
+
 Release 2.7.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/util/CountersStrings.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/util/CountersStrings.java
index ce799f5f2b6..ac16c127c29 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/util/CountersStrings.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/util/CountersStrings.java
@@ -151,25 +151,12 @@ public class CountersStrings {
   public static <C extends Counter, G extends CounterGroupBase<C>,
                  T extends AbstractCounters<C, G>>
   String toEscapedCompactString(T counters) {
-    String[] groupsArray;
-    int length = 0;
+    StringBuilder builder = new StringBuilder();
     synchronized(counters) {
-      groupsArray = new String[counters.countCounters()];
-      int i = 0;
-      // First up, obtain the escaped string for each group so that we can
-      // determine the buffer length apriori.
       for (G group : counters) {
-        String escapedString = toEscapedCompactString(group);
-        groupsArray[i++] = escapedString;
-        length += escapedString.length();
+        builder.append(toEscapedCompactString(group));
       }
     }
-
-    // Now construct the buffer
-    StringBuilder builder = new StringBuilder(length);
-    for (String group : groupsArray) {
-      builder.append(group);
-    }
     return builder.toString();
   }
 
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapred/TestCounters.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapred/TestCounters.java
index 46e7221a83b..5e2763e0036 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapred/TestCounters.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapred/TestCounters.java
@@ -18,6 +18,7 @@
 package org.apache.hadoop.mapred;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import java.io.IOException;
@@ -84,6 +85,8 @@ public class TestCounters {
    */
   private void testCounter(Counters counter) throws ParseException {
     String compactEscapedString = counter.makeEscapedCompactString();
+    assertFalse("compactEscapedString should not contain null",
+                compactEscapedString.contains("null"));
     
     Counters recoveredCounter = 
       Counters.fromEscapedCompactString(compactEscapedString);