MAPREDUCE-6554. MRAppMaster servicestart failing with NPE in MRAppMaster#parsePreviousJobHistory. Contributed by Bibin A Chundatt

(cherry picked from commit 296ecbd5ec9f7d2eed84217a3318b4a3bcd7bd99)

Conflicts:

	hadoop-mapreduce-project/CHANGES.txt

hadoop-mapreduce-project/CHANGES.txt

@@ -27,6 +27,9 @@ Release 2.6.4 - UNRELEASED
     MAPREDUCE-6363. [NNBench] Lease mismatch error when running with multiple
     mappers. (Vlad Sharanhovich and Bibin A Chundatt via aajisaka)
 
+    MAPREDUCE-6554. MRAppMaster servicestart failing with NPE in
+    MRAppMaster#parsePreviousJobHistory (Bibin A Chundatt via jlowe)
+
 Release 2.6.3 - 2015-12-17
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/jobhistory/EventReader.java

@@ -20,9 +20,16 @@ package org.apache.hadoop.mapreduce.jobhistory;
 
 import java.io.Closeable;
 import java.io.DataInputStream;
-import java.io.IOException;
 import java.io.EOFException;
+import java.io.IOException;
 
+import org.apache.avro.AvroRuntimeException;
+import org.apache.avro.Schema;
+import org.apache.avro.io.DatumReader;
+import org.apache.avro.io.Decoder;
+import org.apache.avro.io.DecoderFactory;
+import org.apache.avro.specific.SpecificData;
+import org.apache.avro.specific.SpecificDatumReader;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.fs.FileSystem;
@@ -31,13 +38,6 @@ import org.apache.hadoop.mapreduce.CounterGroup;
 import org.apache.hadoop.mapreduce.Counters;
 import org.apache.hadoop.util.StringInterner;
 
-import org.apache.avro.Schema;
-import org.apache.avro.io.Decoder;
-import org.apache.avro.io.DecoderFactory;
-import org.apache.avro.io.DatumReader;
-import org.apache.avro.specific.SpecificData;
-import org.apache.avro.specific.SpecificDatumReader;
-
 @InterfaceAudience.Private
 @InterfaceStability.Unstable
 public class EventReader implements Closeable {
@@ -72,9 +72,18 @@ public class EventReader implements Closeable {
     }
 
     Schema myschema = new SpecificData(Event.class.getClassLoader()).getSchema(Event.class);
-    this.schema = Schema.parse(in.readLine());
-    this.reader = new SpecificDatumReader(schema, myschema);
-    this.decoder = DecoderFactory.get().jsonDecoder(schema, in);
+    String eventschema = in.readLine();
+    if (null != eventschema) {
+      try {
+        this.schema = Schema.parse(eventschema);
+        this.reader = new SpecificDatumReader(schema, myschema);
+        this.decoder = DecoderFactory.get().jsonDecoder(schema, in);
+      } catch (AvroRuntimeException e) {
+        throw new IOException(e);
+      }
+    } else {
+      throw new IOException("Event schema string not parsed since its null");
+    }
   }
   
   /**