From 28b6d90a93b4949a054a3b103fb7b34b027f0175 Mon Sep 17 00:00:00 2001
From: Jean-Daniel Cryans <jdcryans@apache.org>
Date: Mon, 7 Dec 2009 23:39:26 +0000
Subject: [PATCH] HBASE-2022  NPE in housekeeping kills RS

git-svn-id: https://svn.apache.org/repos/asf/hadoop/hbase/trunk@888193 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES.txt                                               | 1 +
 .../apache/hadoop/hbase/regionserver/HRegionServer.java   | 8 ++++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 646216120bc..ca7a7fc66f2 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -121,6 +121,7 @@ Release 0.21.0 - Unreleased
    HBASE-2018  Updates to .META. blocked under high MemStore load
    HBASE-1994  Master will lose hlog entries while splitting if region has
                empty oldlogfile.log (Lars George via Stack)
+   HBASE-2022  NPE in housekeeping kills RS
 
   IMPROVEMENTS
    HBASE-1760  Cleanup TODOs in HTable
diff --git a/src/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java b/src/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java
index d135a5d042a..26fc1881839 100644
--- a/src/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java
+++ b/src/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java
@@ -1122,9 +1122,13 @@ public class HRegionServer implements HConstants, HRegionInterface,
     if (this.toDo.isEmpty()) {
       return;
     }
-    // This iterator is 'safe'.  We are guaranteed a view on state of the
-    // queue at time iterator was taken out.  Apparently goes from oldest.
+    // This iterator isn't safe if elements are gone and HRS.Worker could
+    // remove them (it already checks for null there). Goes from oldest.
     for (ToDoEntry e: this.toDo) {
+      if(e == null) {
+        LOG.warn("toDo gave a null entry during iteration");
+        break;
+      }
       HMsg msg = e.msg;
       if (msg != null) {
         if (msg.isType(HMsg.Type.MSG_REGION_OPEN)) {