MAPREDUCE-2094. LineRecordReader should not seek into non-splittable, compressed streams.

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/pom.xml

@@ -93,6 +93,7 @@
             <exclude>.gitattributes</exclude>
             <exclude>src/test/resources/recordSpanningMultipleSplits.txt</exclude>
             <exclude>src/test/resources/testBOM.txt</exclude>
+            <exclude>src/test/resources/TestSafeguardSplittingUnsplittableFiles.txt.gz</exclude>
           </excludes>
         </configuration>
       </plugin>

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/FileInputFormat.java

@@ -57,9 +57,12 @@ import com.google.common.collect.Iterables;
  * <p><code>FileInputFormat</code> is the base class for all file-based 
  * <code>InputFormat</code>s. This provides a generic implementation of
  * {@link #getSplits(JobConf, int)}.
- * Subclasses of <code>FileInputFormat</code> can also override the 
+ *
- * {@link #isSplitable(FileSystem, Path)} method to ensure input-files are
+ * Implementations of <code>FileInputFormat</code> can also override the
- * not split-up and are processed as a whole by {@link Mapper}s.
+ * {@link #isSplitable(FileSystem, Path)} method to prevent input files
+ * from being split-up in certain situations. Implementations that may
+ * deal with non-splittable files <i>must</i> override this method, since
+ * the default implementation assumes splitting is always possible.
  */
 @InterfaceAudience.Public
 @InterfaceStability.Stable
@@ -116,9 +119,13 @@ public abstract class FileInputFormat<K, V> implements InputFormat<K, V> {
   }
 
   /**
-   * Is the given filename splitable? Usually, true, but if the file is
+   * Is the given filename splittable? Usually, true, but if the file is
    * stream compressed, it will not be.
    *
+   * The default implementation in <code>FileInputFormat</code> always returns
+   * true. Implementations that may deal with non-splittable files <i>must</i>
+   * override this method.
+   *
    * <code>FileInputFormat</code> implementations can override this and return
    * <code>false</code> to ensure that individual input files are never split-up
    * so that {@link Mapper}s process entire files.

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/LineRecordReader.java

@@ -118,6 +118,13 @@ public class LineRecordReader implements RecordReader<LongWritable, Text> {
         end = cIn.getAdjustedEnd();
         filePosition = cIn; // take pos from compressed stream
       } else {
+        if (start != 0) {
+          // So we have a split that is part of a file stored using
+          // a Compression codec that cannot be split.
+          throw new IOException("Cannot seek in " +
+              codec.getClass().getSimpleName() + " compressed stream");
+        }
+
         in = new SplitLineReader(codec.createInputStream(fileIn,
             decompressor), job, recordDelimiter);
         filePosition = fileIn;

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

@@ -55,9 +55,12 @@ import com.google.common.collect.Lists;
  * <p><code>FileInputFormat</code> is the base class for all file-based 
  * <code>InputFormat</code>s. This provides a generic implementation of
  * {@link #getSplits(JobContext)}.
- * Subclasses of <code>FileInputFormat</code> can also override the 
+ *
- * {@link #isSplitable(JobContext, Path)} method to ensure input-files are
+ * Implementations of <code>FileInputFormat</code> can also override the
- * not split-up and are processed as a whole by {@link Mapper}s.
+ * {@link #isSplitable(JobContext, Path)} method to prevent input files
+ * from being split-up in certain situations. Implementations that may
+ * deal with non-splittable files <i>must</i> override this method, since
+ * the default implementation assumes splitting is always possible.
  */
 @InterfaceAudience.Public
 @InterfaceStability.Stable
@@ -146,9 +149,13 @@ public abstract class FileInputFormat<K, V> extends InputFormat<K, V> {
   }
 
   /**
-   * Is the given filename splitable? Usually, true, but if the file is
+   * Is the given filename splittable? Usually, true, but if the file is
    * stream compressed, it will not be.
    *
+   * The default implementation in <code>FileInputFormat</code> always returns
+   * true. Implementations that may deal with non-splittable files <i>must</i>
+   * override this method.
+   *
    * <code>FileInputFormat</code> implementations can override this and return
    * <code>false</code> to ensure that individual input files are never split-up
    * so that {@link Mapper}s process entire files.

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

@@ -99,6 +99,13 @@ public class LineRecordReader extends RecordReader<LongWritable, Text> {
         end = cIn.getAdjustedEnd();
         filePosition = cIn;
       } else {
+        if (start != 0) {
+          // So we have a split that is only part of a file stored using
+          // a Compression codec that cannot be split.
+          throw new IOException("Cannot seek in " +
+              codec.getClass().getSimpleName() + " compressed stream");
+        }
+
         in = new SplitLineReader(codec.createInputStream(fileIn,
             decompressor), job, this.recordDelimiterBytes);
         filePosition = fileIn;

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapred/TestLineRecordReader.java

@@ -127,6 +127,13 @@ public class TestLineRecordReader {
     testSplitRecords("blockEndingInCR.txt.bz2", 136494);
   }
 
+  @Test(expected=IOException.class)
+  public void testSafeguardSplittingUnsplittableFiles() throws IOException {
+    // The LineRecordReader must fail when trying to read a file that
+    // was compressed using an unsplittable file format
+    testSplitRecords("TestSafeguardSplittingUnsplittableFiles.txt.gz", 2);
+  }
+
   // Use the LineRecordReader to read records from the file
   public ArrayList<String> readRecords(URL testFileUrl, int splitSize)
       throws IOException {

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/lib/input/TestLineRecordReader.java

@@ -110,6 +110,13 @@ public class TestLineRecordReader {
     testSplitRecords("blockEndingInCRThenLF.txt.bz2", 136498);
   }
 
+  @Test(expected=IOException.class)
+  public void testSafeguardSplittingUnsplittableFiles() throws IOException {
+    // The LineRecordReader must fail when trying to read a file that
+    // was compressed using an unsplittable file format
+    testSplitRecords("TestSafeguardSplittingUnsplittableFiles.txt.gz", 2);
+  }
+
   // Use the LineRecordReader to read records from the file
   public ArrayList<String> readRecords(URL testFileUrl, int splitSize)
       throws IOException {

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/resources/TestSafeguardSplittingUnsplittableFiles.txt.gz

@@ -0,0 +1 @@
+Hello World