From ba1f9d66d94ed0b85084d7c40c09a87478b3a05a Mon Sep 17 00:00:00 2001
From: Jason Lowe <jlowe@apache.org>
Date: Tue, 6 Nov 2018 17:55:51 -0600
Subject: [PATCH] MAPREDUCE-7156. NullPointerException when reaching max
 shuffle connections. Contributed by Peter Bacsko

---
 .../main/java/org/apache/hadoop/mapred/ShuffleHandler.java    | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
index aeda9cc688..c2226855fd 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
@@ -910,6 +910,8 @@ private List<String> splitMaps(List<String> mapq) {
     @Override
     public void channelOpen(ChannelHandlerContext ctx, ChannelStateEvent evt) 
         throws Exception {
+      super.channelOpen(ctx, evt);
+
       if ((maxShuffleConnections > 0) && (accepted.size() >= maxShuffleConnections)) {
         LOG.info(String.format("Current number of shuffle connections (%d) is " + 
             "greater than or equal to the max allowed shuffle connections (%d)", 
@@ -925,8 +927,6 @@ public void channelOpen(ChannelHandlerContext ctx, ChannelStateEvent evt)
         return;
       }
       accepted.add(evt.getChannel());
-      super.channelOpen(ctx, evt);
-     
     }
 
     @Override