HADOOP-610. Fix a problem when the DFS block size is configured to be smaller than the buffer size. Contributed by Milind.

git-svn-id: https://svn.apache.org/repos/asf/lucene/hadoop/trunk@475371 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -81,6 +81,10 @@ Trunk (unreleased changes)
     compression.  To build this, specify -Dcompile.native to Ant.
     (Arun C Murthy via cutting)
 
+25. HADOOP-610.  Fix an problem when the DFS block size is configured
+    to be smaller than the buffer size, typically only when debugging.
+    (Milind Bhandarkar via cutting)
+
 
 Release 0.8.0 - 2006-11-03
 

src/java/org/apache/hadoop/dfs/DFSClient.java

@@ -1080,7 +1080,8 @@ class DFSClient implements FSConstants {
                 throw new IOException("Stream closed");
             }
             while (len > 0) {
-              int remaining = BUFFER_SIZE - pos;
+              int remaining = Math.min(BUFFER_SIZE - pos,
+                  (int)((blockSize - bytesWrittenToBlock) - pos));
               int toWrite = Math.min(remaining, len);
               System.arraycopy(b, off, outBuf, pos, toWrite);
               pos += toWrite;

src/test/org/apache/hadoop/dfs/TestSmallBlock.java

@@ -0,0 +1,96 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.dfs;
+
+import junit.framework.TestCase;
+import java.io.*;
+import java.util.Random;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FSInputStream;
+import org.apache.hadoop.fs.FSOutputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+
+/**
+ * This class tests the creation of files with block-size
+ * smaller than the default buffer size of 4K.
+ * @author Milind Bhandarkar
+ */
+public class TestSmallBlock extends TestCase {
+  static final long seed = 0xDEADBEEFL;
+  static final int blockSize = 1;
+  static final int fileSize = 20;
+
+  private void writeFile(FileSystem fileSys, Path name) throws IOException {
+    // create and write a file that contains three blocks of data
+    FSOutputStream stm = fileSys.createRaw(name, true, (short)1,
+        (long)blockSize);
+    byte[] buffer = new byte[fileSize];
+    Random rand = new Random(seed);
+    rand.nextBytes(buffer);
+    stm.write(buffer);
+    stm.close();
+  }
+  
+  private void checkAndEraseData(byte[] actual, int from, byte[] expected, String message) {
+    for (int idx = 0; idx < actual.length; idx++) {
+      this.assertEquals(message+" byte "+(from+idx)+" differs. expected "+
+          expected[from+idx]+" actual "+actual[idx],
+          actual[idx], expected[from+idx]);
+      actual[idx] = 0;
+    }
+  }
+  
+  private void checkFile(FileSystem fileSys, Path name) throws IOException {
+    String[][] locations = fileSys.getFileCacheHints(name, 0, fileSize);
+    assertEquals("Number of blocks", fileSize, locations.length);
+    FSInputStream stm = fileSys.openRaw(name);
+    byte[] expected = new byte[fileSize];
+    Random rand = new Random(seed);
+    rand.nextBytes(expected);
+    // do a sanity check. Read the file
+    byte[] actual = new byte[fileSize];
+    stm.readFully(0, actual);
+    checkAndEraseData(actual, 0, expected, "Read Sanity Test");
+    stm.close();
+  }
+  
+  private void cleanupFile(FileSystem fileSys, Path name) throws IOException {
+    assertTrue(fileSys.exists(name));
+    fileSys.delete(name);
+    assertTrue(!fileSys.exists(name));
+  }
+  
+  /**
+   * Tests small block size in in DFS.
+   */
+  public void testSmallBlock() throws IOException {
+    Configuration conf = new Configuration();
+    MiniDFSCluster cluster = new MiniDFSCluster(65312, conf, 1, false);
+    FileSystem fileSys = cluster.getFileSystem();
+    try {
+      Path file1 = new Path("smallblocktest.dat");
+      writeFile(fileSys, file1);
+      checkFile(fileSys, file1);
+      cleanupFile(fileSys, file1);
+    } finally {
+      fileSys.close();
+      cluster.shutdown();
+    }
+  }
+}