HDFS-5343. When cat command is issued on snapshot files, getting unexpected result. Contributed by Sathish.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1561325 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -1137,6 +1137,9 @@ Release 2.3.0 - UNRELEASED
 
     HDFS-5789. Some of snapshot APIs missing checkOperation double check in fsn. (umamahesh)
 
+    HDFS-5343. When cat command is issued on snapshot files getting unexpected result.
+    (Sathish via umamahesh)
+
 Release 2.2.0 - 2013-10-13
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java

@@ -792,6 +792,9 @@ private int readWithStrategy(ReaderStrategy strategy, int off, int len) throws I
             currentNode = blockSeekTo(pos);
           }
           int realLen = (int) Math.min(len, (blockEnd - pos + 1L));
+          if (locatedBlocks.isLastBlockComplete()) {
+            realLen = (int) Math.min(realLen, locatedBlocks.getFileLength());
+          }
           int result = readBuffer(strategy, off, realLen, corruptedBlockMap);
           
           if (result >= 0) {

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotFileLength.java

@@ -17,22 +17,26 @@
  */
 package org.apache.hadoop.hdfs.server.namenode.snapshot;
 
-import java.util.Random;
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+
 
 import org.apache.hadoop.fs.FileStatus;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import static org.hamcrest.CoreMatchers.is;
-import static org.junit.Assert.assertThat;
+import static org.junit.Assert.*;
-import static org.junit.Assert.assertTrue;
+
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.FsShell;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.util.ToolRunner;
 
 public class TestSnapshotFileLength {
 
@@ -112,4 +116,61 @@ public void testSnapshotfileLength() throws Exception {
     assertThat(bytesRead, is(BLOCKSIZE));
     fis.close();
   }
+
+  /**
+   * Adding as part of jira HDFS-5343
+   * Test for checking the cat command on snapshot path it
+   *  cannot read a file beyond snapshot file length
+   * @throws Exception
+   */
+  @Test (timeout = 600000)
+  public void testSnapshotFileLengthWithCatCommand() throws Exception {
+
+    FSDataInputStream fis = null;
+    FileStatus fileStatus = null;
+
+    int bytesRead;
+    byte[] buffer = new byte[BLOCKSIZE * 8];
+
+    hdfs.mkdirs(sub);
+    Path file1 = new Path(sub, file1Name);
+    DFSTestUtil.createFile(hdfs, file1, BLOCKSIZE, REPLICATION, SEED);
+
+    hdfs.allowSnapshot(sub);
+    hdfs.createSnapshot(sub, snapshot1);
+
+    DFSTestUtil.appendFile(hdfs, file1, BLOCKSIZE);
+
+    // Make sure we can read the entire file via its non-snapshot path.
+    fileStatus = hdfs.getFileStatus(file1);
+    assertEquals(fileStatus.getLen(), BLOCKSIZE * 2);
+    fis = hdfs.open(file1);
+    bytesRead = fis.read(buffer, 0, buffer.length);
+    assertEquals(bytesRead, BLOCKSIZE * 2);
+    fis.close();
+
+    Path file1snap1 =
+        SnapshotTestHelper.getSnapshotPath(sub, snapshot1, file1Name);
+    fis = hdfs.open(file1snap1);
+    fileStatus = hdfs.getFileStatus(file1snap1);
+    assertEquals(fileStatus.getLen(), BLOCKSIZE);
+    // Make sure we can only read up to the snapshot length.
+    bytesRead = fis.read(buffer, 0, buffer.length);
+    assertEquals(bytesRead, BLOCKSIZE);
+    fis.close();
+
+    PrintStream psBackup = System.out;
+    ByteArrayOutputStream bao = new ByteArrayOutputStream();
+    System.setOut(new PrintStream(bao));
+    System.setErr(new PrintStream(bao));
+    // Make sure we can cat the file upto to snapshot length
+    FsShell shell = new FsShell();
+    try{
+      ToolRunner.run(conf, shell, new String[] { "-cat",
+      "/TestSnapshotFileLength/sub1/.snapshot/snapshot1/file1" });
+      assertEquals(bao.size(), BLOCKSIZE);
+    }finally{
+      System.setOut(psBackup);
+    }
+  }
 }