MAPREDUCE-4782. NLineInputFormat skips first line of last InputSplit (Mark Fuhs via bobby)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1407505 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -641,6 +641,9 @@ Release 0.23.5 - UNRELEASED
     MAPREDUCE-4772. Fetch failures can take way too long for a map to be 
     restarted (bobby)
 
+    MAPREDUCE-4782. NLineInputFormat skips first line of last InputSplit 
+    (Mark Fuhs via bobby)
+ 
 Release 0.23.4 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/lib/input/NLineInputFormat.java

@@ -107,25 +107,14 @@ public class NLineInputFormat extends FileInputFormat<LongWritable, Text> {
         numLines++;
         length += num;
         if (numLines == numLinesPerSplit) {
-          // NLineInputFormat uses LineRecordReader, which always reads
+          splits.add(createFileSplit(fileName, begin, length));
-          // (and consumes) at least one character out of its upper split
-          // boundary. So to make sure that each mapper gets N lines, we
-          // move back the upper split limits of each split 
-          // by one character here.
-          if (begin == 0) {
-            splits.add(new FileSplit(fileName, begin, length - 1,
-              new String[] {}));
-          } else {
-            splits.add(new FileSplit(fileName, begin - 1, length,
-              new String[] {}));
-          }
           begin += length;
           length = 0;
           numLines = 0;
         }
       }
       if (numLines != 0) {
-        splits.add(new FileSplit(fileName, begin, length, new String[]{}));
+        splits.add(createFileSplit(fileName, begin, length));
       }
     } finally {
       if (lr != null) {
@@ -135,6 +124,23 @@ public class NLineInputFormat extends FileInputFormat<LongWritable, Text> {
     return splits; 
   }
 
+  /**
+   * NLineInputFormat uses LineRecordReader, which always reads
+   * (and consumes) at least one character out of its upper split
+   * boundary. So to make sure that each mapper gets N lines, we
+   * move back the upper split limits of each split 
+   * by one character here.
+   * @param fileName  Path of file
+   * @param begin  the position of the first byte in the file to process
+   * @param length  number of bytes in InputSplit
+   * @return  FileSplit
+   */
+  protected static FileSplit createFileSplit(Path fileName, long begin, long length) {
+    return (begin == 0) 
+    ? new FileSplit(fileName, begin, length - 1, new String[] {})
+    : new FileSplit(fileName, begin - 1, length, new String[] {});
+  }
+  
   /**
    * Set the number of lines per split
    * @param job the job to modify

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/src/test/java/org/apache/hadoop/mapreduce/lib/input/TestNLineInputFormat.java

@@ -50,37 +50,40 @@ public class TestNLineInputFormat extends TestCase {
     Job job = Job.getInstance(conf);
     Path file = new Path(workDir, "test.txt");
 
-    int seed = new Random().nextInt();
-    Random random = new Random(seed);
-
     localFs.delete(workDir, true);
     FileInputFormat.setInputPaths(job, workDir);
     int numLinesPerMap = 5;
     NLineInputFormat.setNumLinesPerSplit(job, numLinesPerMap);
-    // for a variety of lengths
     for (int length = 0; length < MAX_LENGTH;
-         length += random.nextInt(MAX_LENGTH / 10) + 1) {
+         length += 1) {
+ 
       // create a file with length entries
       Writer writer = new OutputStreamWriter(localFs.create(file));
       try {
         for (int i = 0; i < length; i++) {
-          writer.write(Integer.toString(i));
+          writer.write(Integer.toString(i)+" some more text");
           writer.write("\n");
         }
       } finally {
         writer.close();
       }
-      checkFormat(job, numLinesPerMap);
+      int lastN = 0;
+      if (length != 0) {
+        lastN = length % 5;
+        if (lastN == 0) {
+          lastN = 5;
+        }
+      }
+      checkFormat(job, numLinesPerMap, lastN);
     }
   }
 
-  void checkFormat(Job job, int expectedN) 
+  void checkFormat(Job job, int expectedN, int lastN) 
       throws IOException, InterruptedException {
     NLineInputFormat format = new NLineInputFormat();
     List<InputSplit> splits = format.getSplits(job);
-    // check all splits except last one
     int count = 0;
-    for (int i = 0; i < splits.size() -1; i++) {
+    for (int i = 0; i < splits.size(); i++) {
       assertEquals("There are no split locations", 0,
                    splits.get(i).getLocations().length);
       TaskAttemptContext context = MapReduceTestUtil.
@@ -104,10 +107,15 @@ public class TestNLineInputFormat extends TestCase {
       } finally {
         reader.close();
       }
-      assertEquals("number of lines in split is " + expectedN ,
+      if ( i == splits.size() - 1) {
+        assertEquals("number of lines in split(" + i + ") is wrong" ,
+                     lastN, count);
+      } else {
+        assertEquals("number of lines in split(" + i + ") is wrong" ,
                      expectedN, count);
       }
     }
+  }
   
   public static void main(String[] args) throws Exception {
     new TestNLineInputFormat().testFormat();