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From t...@apache.org
Subject svn commit: r1338492 - in /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs: ./ src/main/java/org/apache/hadoop/hdfs/server/namenode/ src/main/java/org/apache/hadoop/hdfs/tools/offlineEditsViewer/ src/test/java/org/apache/hadoop/hdfs/server/namenode/
Date Tue, 15 May 2012 00:41:38 GMT
Author: todd
Date: Tue May 15 00:41:37 2012
New Revision: 1338492

URL: http://svn.apache.org/viewvc?rev=1338492&view=rev
Log:
HDFS-3335. check for edit log corruption at the end of the log. Contributed by Colin Patrick
McCabe.

Modified:
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineEditsViewer/OfflineEditsLoader.java
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLog.java
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLogFileOutputStream.java
    hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNameNodeRecovery.java

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt (original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt Tue May 15 00:41:37 2012
@@ -459,6 +459,9 @@ Release 2.0.0 - UNRELEASED 
     HDFS-3404. Make putImage in GetImageServlet infer remote address to fetch
     from request. (atm)
 
+    HDFS-3335. check for edit log corruption at the end of the log
+    (Colin Patrick McCabe via todd)
+
   OPTIMIZATIONS
 
     HDFS-3024. Improve performance of stringification in addStoredBlock (todd)

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java
Tue May 15 00:41:37 2012
@@ -106,7 +106,35 @@ public class EditLogFileInputStream exte
 
   @Override
   protected FSEditLogOp nextOp() throws IOException {
-    return reader.readOp(false);
+    FSEditLogOp op = reader.readOp(false);
+    if ((op != null) && (op.hasTransactionId())) {
+      long txId = op.getTransactionId();
+      if ((txId >= lastTxId) &&
+          (lastTxId != HdfsConstants.INVALID_TXID)) {
+        //
+        // Sometimes, the NameNode crashes while it's writing to the
+        // edit log.  In that case, you can end up with an unfinalized edit log
+        // which has some garbage at the end.
+        // JournalManager#recoverUnfinalizedSegments will finalize these
+        // unfinished edit logs, giving them a defined final transaction 
+        // ID.  Then they will be renamed, so that any subsequent
+        // readers will have this information.
+        //
+        // Since there may be garbage at the end of these "cleaned up"
+        // logs, we want to be sure to skip it here if we've read everything
+        // we were supposed to read out of the stream.
+        // So we force an EOF on all subsequent reads.
+        //
+        long skipAmt = file.length() - tracker.getPos();
+        if (skipAmt > 0) {
+          FSImage.LOG.warn("skipping " + skipAmt + " bytes at the end " +
+              "of edit log  '" + getName() + "': reached txid " + txId +
+              " out of " + lastTxId);
+          tracker.skip(skipAmt);
+        }
+      }
+    }
+    return op;
   }
   
   @Override

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java
Tue May 15 00:41:37 2012
@@ -41,12 +41,13 @@ import com.google.common.annotations.Vis
 @InterfaceAudience.Private
 public class EditLogFileOutputStream extends EditLogOutputStream {
   private static Log LOG = LogFactory.getLog(EditLogFileOutputStream.class);
+  public static final int PREALLOCATION_LENGTH = 1024 * 1024;
 
   private File file;
   private FileOutputStream fp; // file stream for storing edit logs
   private FileChannel fc; // channel of the file stream for sync
   private EditsDoubleBuffer doubleBuf;
-  static ByteBuffer fill = ByteBuffer.allocateDirect(1024 * 1024); // preallocation, 1MB
+  static ByteBuffer fill = ByteBuffer.allocateDirect(PREALLOCATION_LENGTH);
 
   static {
     fill.position(0);

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
Tue May 15 00:41:37 2012
@@ -144,7 +144,7 @@ public class FSEditLogLoader {
             check203UpgradeFailure(logVersion, e);
             String errorMessage =
               formatEditLogReplayError(in, recentOpcodeOffsets, expectedTxId);
-            FSImage.LOG.error(errorMessage);
+            FSImage.LOG.error(errorMessage, e);
             if (recovery == null) {
                // We will only try to skip over problematic opcodes when in
                // recovery mode.
@@ -730,29 +730,34 @@ public class FSEditLogLoader {
       super(is);
     }
 
+    @Override
     public int read() throws IOException {
       int ret = super.read();
       if (ret != -1) curPos++;
       return ret;
     }
 
+    @Override
     public int read(byte[] data) throws IOException {
       int ret = super.read(data);
       if (ret > 0) curPos += ret;
       return ret;
     }
 
+    @Override
     public int read(byte[] data, int offset, int length) throws IOException {
       int ret = super.read(data, offset, length);
       if (ret > 0) curPos += ret;
       return ret;
     }
 
+    @Override
     public void mark(int limit) {
       super.mark(limit);
       markPos = curPos;
     }
 
+    @Override
     public void reset() throws IOException {
       if (markPos == -1) {
         throw new IOException("Not marked!");
@@ -765,6 +770,13 @@ public class FSEditLogLoader {
     public long getPos() {
       return curPos;
     }
+    
+    @Override
+    public long skip(long amt) throws IOException {
+      long ret = super.skip(amt);
+      curPos += ret;
+      return ret;
+    }
   }
 
   public long getLastAppliedTxId() {

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
Tue May 15 00:41:37 2012
@@ -75,6 +75,7 @@ import java.io.EOFException;
 public abstract class FSEditLogOp {
   public final FSEditLogOpCodes opCode;
   long txid;
+  private static final int MAX_OP_SIZE = 100 * 1024 * 1024;
 
 
   @SuppressWarnings("deprecation")
@@ -2263,30 +2264,75 @@ public abstract class FSEditLogOp {
      * 
      * @param skipBrokenEdits    If true, attempt to skip over damaged parts of
      * the input stream, rather than throwing an IOException
-     * @return the operation read from the stream, or null at the end of the file
-     * @throws IOException on error.
+     * @return the operation read from the stream, or null at the end of the 
+     *         file
+     * @throws IOException on error.  This function should only throw an
+     *         exception when skipBrokenEdits is false.
      */
     public FSEditLogOp readOp(boolean skipBrokenEdits) throws IOException {
-      FSEditLogOp op = null;
       while (true) {
         try {
-          in.mark(in.available());
-          try {
-            op = decodeOp();
-          } finally {
-            // If we encountered an exception or an end-of-file condition,
-            // do not advance the input stream.
-            if (op == null) {
-              in.reset();
-            }
+          in.mark(MAX_OP_SIZE);
+          return decodeOp();
+        } catch (GarbageAfterTerminatorException e) {
+          in.reset();
+          if (!skipBrokenEdits) {
+            throw e;
+          }
+          // If we saw a terminator opcode followed by a long region of 0x00 or
+          // 0xff, we want to skip over that region, because there's nothing
+          // interesting there.
+          long numSkip = e.getNumAfterTerminator();
+          if (in.skip(numSkip) < numSkip) {
+            FSImage.LOG.error("Failed to skip " + numSkip + " bytes of " +
+              "garbage after an OP_INVALID.  Unexpected early EOF.");
+            return null;
           }
-          return op;
         } catch (IOException e) {
+          in.reset();
           if (!skipBrokenEdits) {
             throw e;
           }
-          if (in.skip(1) < 1) {
-            return null;
+        } catch (RuntimeException e) {
+          // FSEditLogOp#decodeOp is not supposed to throw RuntimeException.
+          // However, we handle it here for recovery mode, just to be more
+          // robust.
+          in.reset();
+          if (!skipBrokenEdits) {
+            throw e;
+          }
+        } catch (Throwable e) {
+          in.reset();
+          if (!skipBrokenEdits) {
+            throw new IOException("got unexpected exception " +
+                e.getMessage(), e);
+          }
+        }
+        // Move ahead one byte and re-try the decode process.
+        if (in.skip(1) < 1) {
+          return null;
+        }
+      }
+    }
+
+    private void verifyTerminator() throws IOException {
+      long off = 0;
+      /** The end of the edit log should contain only 0x00 or 0xff bytes.
+       * If it contains other bytes, the log itself may be corrupt.
+       * It is important to check this; if we don't, a stray OP_INVALID byte 
+       * could make us stop reading the edit log halfway through, and we'd never
+       * know that we had lost data.
+       */
+      byte[] buf = new byte[4096];
+      while (true) {
+        int numRead = in.read(buf);
+        if (numRead == -1) {
+          return;
+        }
+        for (int i = 0; i < numRead; i++, off++) {
+          if ((buf[i] != (byte)0) && (buf[i] != (byte)-1)) {
+            throw new GarbageAfterTerminatorException("Read garbage after " +
+            		"the terminator!", off);
           }
         }
       }
@@ -2306,8 +2352,10 @@ public abstract class FSEditLogOp {
       }
 
       FSEditLogOpCodes opCode = FSEditLogOpCodes.fromByte(opCodeByte);
-      if (opCode == OP_INVALID)
+      if (opCode == OP_INVALID) {
+        verifyTerminator();
         return null;
+      }
 
       FSEditLogOp op = cache.get(opCode);
       if (op == null) {
@@ -2477,4 +2525,35 @@ public abstract class FSEditLogOp {
     short mode = Short.valueOf(st.getValue("MODE"));
     return new PermissionStatus(username, groupname, new FsPermission(mode));
   }
-		}
+
+  /**
+   * Exception indicating that we found an OP_INVALID followed by some 
+   * garbage.  An OP_INVALID should signify the end of the file... if there 
+   * is additional content after that, then the edit log is corrupt. 
+   */
+  static class GarbageAfterTerminatorException extends IOException {
+    private static final long serialVersionUID = 1L;
+    private final long numAfterTerminator;
+
+    public GarbageAfterTerminatorException(String str,
+        long numAfterTerminator) {
+      super(str);
+      this.numAfterTerminator = numAfterTerminator;
+    }
+
+    /**
+     * Get the number of bytes after the terminator at which the garbage
+     * appeared.
+     *
+     * So if you had an OP_INVALID followed immediately by another valid opcode,
+     * this would be 0.
+     * If you had an OP_INVALID followed by some padding bytes, followed by a
+     * stray byte at the end, this would be the number of padding bytes.
+     * 
+     * @return numAfterTerminator
+     */
+    public long getNumAfterTerminator() {
+      return numAfterTerminator;
+    }
+  }
+}

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java
Tue May 15 00:41:37 2012
@@ -60,6 +60,7 @@ import org.apache.hadoop.hdfs.DFSConfigK
 import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.HAUtil;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Joiner;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
@@ -536,6 +537,11 @@ public class FSImage implements Closeabl
     return editLog;
   }
 
+  @VisibleForTesting
+  void setEditLogForTesting(FSEditLog newLog) {
+    editLog = newLog;
+  }
+
   void openEditLogForWrite() throws IOException {
     assert editLog != null : "editLog must be initialized";
     editLog.openForWrite();

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineEditsViewer/OfflineEditsLoader.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineEditsViewer/OfflineEditsLoader.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineEditsViewer/OfflineEditsLoader.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineEditsViewer/OfflineEditsLoader.java
Tue May 15 00:41:37 2012
@@ -22,6 +22,7 @@ import java.io.IOException;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 
+import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.server.namenode.EditLogFileInputStream;
 
 import org.apache.hadoop.hdfs.server.namenode.EditLogInputStream;
@@ -48,7 +49,8 @@ interface OfflineEditsLoader {
         OfflineEditsLoader loader = null;
         try {
           file = new File(inputFileName);
-          elis = new EditLogFileInputStream(file, -1, -1, false);
+          elis = new EditLogFileInputStream(file, HdfsConstants.INVALID_TXID,
+              HdfsConstants.INVALID_TXID, false);
           loader = new OfflineEditsBinaryLoader(visitor, elis);
         } finally {
           if ((loader == null) && (elis != null)) {

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLog.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLog.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLog.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLog.java
Tue May 15 00:41:37 2012
@@ -527,7 +527,7 @@ public class TestEditLog extends TestCas
     } catch (IOException e) {
       // expected
       assertEquals("Cause of exception should be ChecksumException",
-          e.getCause().getClass(), ChecksumException.class);
+          ChecksumException.class, e.getCause().getClass());
     }
   }
 

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLogFileOutputStream.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLogFileOutputStream.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLogFileOutputStream.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLogFileOutputStream.java
Tue May 15 00:41:37 2012
@@ -68,7 +68,7 @@ public class TestEditLogFileOutputStream
     assertEquals(1, validation.getNumTransactions());
     assertEquals("Edit log should have 1MB pre-allocated, plus 4 bytes " +
         "for the version number",
-        PREALLOCATION_LENGTH, editLog.length());
+        EditLogFileOutputStream.PREALLOCATION_LENGTH + 4, editLog.length());
     
 
     cluster.getFileSystem().mkdirs(new Path("/tmp"),
@@ -82,7 +82,7 @@ public class TestEditLogFileOutputStream
     assertEquals(2, validation.getNumTransactions());
 
     assertEquals("Edit log should be 1MB long, plus 4 bytes for the version number",
-        PREALLOCATION_LENGTH, editLog.length());
+        EditLogFileOutputStream.PREALLOCATION_LENGTH + 4, editLog.length());
     // 256 blocks for the 1MB of preallocation space
     assertTrue("Edit log disk space used should be at least 257 blocks",
         256 * 4096 <= new DU(editLog, conf).getUsed());

Modified: hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNameNodeRecovery.java
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNameNodeRecovery.java?rev=1338492&r1=1338491&r2=1338492&view=diff
==============================================================================
--- hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNameNodeRecovery.java
(original)
+++ hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNameNodeRecovery.java
Tue May 15 00:41:37 2012
@@ -25,6 +25,8 @@ import java.util.HashSet;
 import java.util.Set;
 
 import static org.junit.Assert.*;
+import static org.mockito.Mockito.doNothing;
+import static org.mockito.Mockito.spy;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -37,7 +39,6 @@ import org.apache.hadoop.hdfs.server.com
 import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.OpInstanceCache;
 import org.apache.hadoop.hdfs.server.namenode.FSImage;
-import org.apache.hadoop.hdfs.server.namenode.FSImageTestUtil;
 import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.DeleteOp;
 import org.apache.hadoop.hdfs.server.namenode.NNStorage.NameNodeDirType;
@@ -213,15 +214,129 @@ public class TestNameNodeRecovery {
   public void testSkipEdit() throws IOException {
     runEditLogTest(new EltsTestGarbageInEditLog());
   }
-  
-  /** Test that we can successfully recover from a situation where the last
-   * entry in the edit log has been truncated. */
-  @Test(timeout=180000)
-  public void testRecoverTruncatedEditLog() throws IOException {
+
+  /**
+   * An algorithm for corrupting an edit log.
+   */
+  static interface Corruptor {
+    /*
+     * Corrupt an edit log file.
+     *
+     * @param editFile   The edit log file
+     */
+    public void corrupt(File editFile) throws IOException;
+
+    /*
+     * Explain whether we need to read the log in recovery mode
+     *
+     * @param finalized  True if the edit log in question is finalized.
+     *                   We're a little more lax about reading unfinalized
+     *                   logs.  We will allow a small amount of garbage at
+     *                   the end.  In a finalized log, every byte must be
+     *                   perfect.
+     *
+     * @return           Whether we need to read the log in recovery mode
+     */
+    public boolean needRecovery(boolean finalized);
+
+    /*
+     * Get the name of this corruptor
+     *
+     * @return           The Corruptor name
+     */
+    public String getName();
+  }
+
+  static class TruncatingCorruptor implements Corruptor {
+    @Override
+    public void corrupt(File editFile) throws IOException {
+      // Corrupt the last edit
+      long fileLen = editFile.length();
+      RandomAccessFile rwf = new RandomAccessFile(editFile, "rw");
+      rwf.setLength(fileLen - 1);
+      rwf.close();
+    }
+
+    @Override
+    public boolean needRecovery(boolean finalized) {
+      return finalized;
+    }
+
+    @Override
+    public String getName() {
+      return "truncated";
+    }
+  }
+
+  static class PaddingCorruptor implements Corruptor {
+    @Override
+    public void corrupt(File editFile) throws IOException {
+      // Add junk to the end of the file
+      RandomAccessFile rwf = new RandomAccessFile(editFile, "rw");
+      rwf.seek(editFile.length());
+      for (int i = 0; i < 129; i++) {
+        rwf.write((byte)0);
+      }
+      rwf.write(0xd);
+      rwf.write(0xe);
+      rwf.write(0xa);
+      rwf.write(0xd);
+      rwf.close();
+    }
+
+    @Override
+    public boolean needRecovery(boolean finalized) {
+      // With finalized edit logs, we ignore what's at the end as long as we
+      // can make it to the correct transaction ID.
+      // With unfinalized edit logs, the finalization process ignores garbage
+      // at the end.
+      return false;
+    }
+
+    @Override
+    public String getName() {
+      return "padFatal";
+    }
+  }
+
+  static class SafePaddingCorruptor implements Corruptor {
+    private byte padByte;
+
+    public SafePaddingCorruptor(byte padByte) {
+      this.padByte = padByte;
+      assert ((this.padByte == 0) || (this.padByte == -1));
+    }
+
+    @Override
+    public void corrupt(File editFile) throws IOException {
+      // Add junk to the end of the file
+      RandomAccessFile rwf = new RandomAccessFile(editFile, "rw");
+      rwf.seek(editFile.length());
+      rwf.write((byte)-1);
+      for (int i = 0; i < 1024; i++) {
+        rwf.write(padByte);
+      }
+      rwf.close();
+    }
+
+    @Override
+    public boolean needRecovery(boolean finalized) {
+      return false;
+    }
+
+    @Override
+    public String getName() {
+      return "pad" + ((int)padByte);
+    }
+  }
+
+  static void testNameNodeRecoveryImpl(Corruptor corruptor, boolean finalize)
+      throws IOException {
     final String TEST_PATH = "/test/path/dir";
     final int NUM_TEST_MKDIRS = 10;
-    
-    // start a cluster 
+    final boolean needRecovery = corruptor.needRecovery(finalize);
+
+    // start a cluster
     Configuration conf = new HdfsConfiguration();
     MiniDFSCluster cluster = null;
     FileSystem fileSys = null;
@@ -230,6 +345,15 @@ public class TestNameNodeRecovery {
       cluster = new MiniDFSCluster.Builder(conf).numDataNodes(0)
           .build();
       cluster.waitActive();
+      if (!finalize) {
+        // Normally, the in-progress edit log would be finalized by
+        // FSEditLog#endCurrentLogSegment.  For testing purposes, we
+        // disable that here.
+        FSEditLog spyLog =
+            spy(cluster.getNameNode().getFSImage().getEditLog());
+        doNothing().when(spyLog).endCurrentLogSegment(true);
+        cluster.getNameNode().getFSImage().setEditLogForTesting(spyLog);
+      }
       fileSys = cluster.getFileSystem();
       final FSNamesystem namesystem = cluster.getNamesystem();
       FSImage fsimage = namesystem.getFSImage();
@@ -246,13 +370,11 @@ public class TestNameNodeRecovery {
     File editFile = FSImageTestUtil.findLatestEditsLog(sd).getFile();
     assertTrue("Should exist: " + editFile, editFile.exists());
 
-    // Corrupt the last edit
-    long fileLen = editFile.length();
-    RandomAccessFile rwf = new RandomAccessFile(editFile, "rw");
-    rwf.setLength(fileLen - 1);
-    rwf.close();
-    
-    // Make sure that we can't start the cluster normally before recovery
+    // Corrupt the edit log
+    corruptor.corrupt(editFile);
+
+    // If needRecovery == true, make sure that we can't start the
+    // cluster normally before recovery
     cluster = null;
     try {
       LOG.debug("trying to start normally (this should fail)...");
@@ -260,16 +382,24 @@ public class TestNameNodeRecovery {
           .format(false).build();
       cluster.waitActive();
       cluster.shutdown();
-      fail("expected the truncated edit log to prevent normal startup");
+      if (needRecovery) {
+        fail("expected the corrupted edit log to prevent normal startup");
+      }
     } catch (IOException e) {
-      // success
+      if (!needRecovery) {
+        LOG.error("Got unexpected failure with " + corruptor.getName() +
+            corruptor, e);
+        fail("got unexpected exception " + e.getMessage());
+      }
     } finally {
       if (cluster != null) {
         cluster.shutdown();
       }
     }
-    
-    // Perform recovery
+
+    // Perform NameNode recovery.
+    // Even if there was nothing wrong previously (needRecovery == false),
+    // this should still work fine.
     cluster = null;
     try {
       LOG.debug("running recovery...");
@@ -277,22 +407,22 @@ public class TestNameNodeRecovery {
           .format(false).startupOption(recoverStartOpt).build();
     } catch (IOException e) {
       fail("caught IOException while trying to recover. " +
-          "message was " + e.getMessage() + 
+          "message was " + e.getMessage() +
           "\nstack trace\n" + StringUtils.stringifyException(e));
     } finally {
       if (cluster != null) {
         cluster.shutdown();
       }
     }
-    
+
     // Make sure that we can start the cluster normally after recovery
     cluster = null;
     try {
       LOG.debug("starting cluster normally after recovery...");
       cluster = new MiniDFSCluster.Builder(conf).numDataNodes(0)
           .format(false).build();
-      LOG.debug("testRecoverTruncatedEditLog: successfully recovered the " +
-          "truncated edit log");
+      LOG.debug("successfully recovered the " + corruptor.getName() +
+          " corrupted edit log");
       assertTrue(cluster.getFileSystem().exists(new Path(TEST_PATH)));
     } catch (IOException e) {
       fail("failed to recover.  Error message: " + e.getMessage());
@@ -302,4 +432,36 @@ public class TestNameNodeRecovery {
       }
     }
   }
+
+  /** Test that we can successfully recover from a situation where the last
+   * entry in the edit log has been truncated. */
+  @Test(timeout=180000)
+  public void testRecoverTruncatedEditLog() throws IOException {
+    testNameNodeRecoveryImpl(new TruncatingCorruptor(), true);
+    testNameNodeRecoveryImpl(new TruncatingCorruptor(), false);
+  }
+
+  /** Test that we can successfully recover from a situation where the last
+   * entry in the edit log has been padded with garbage. */
+  @Test(timeout=180000)
+  public void testRecoverPaddedEditLog() throws IOException {
+    testNameNodeRecoveryImpl(new PaddingCorruptor(), true);
+    testNameNodeRecoveryImpl(new PaddingCorruptor(), false);
+  }
+
+  /** Test that don't need to recover from a situation where the last
+   * entry in the edit log has been padded with 0. */
+  @Test(timeout=180000)
+  public void testRecoverZeroPaddedEditLog() throws IOException {
+    testNameNodeRecoveryImpl(new SafePaddingCorruptor((byte)0), true);
+    testNameNodeRecoveryImpl(new SafePaddingCorruptor((byte)0), false);
+  }
+
+  /** Test that don't need to recover from a situation where the last
+   * entry in the edit log has been padded with 0xff bytes. */
+  @Test(timeout=180000)
+  public void testRecoverNegativeOnePaddedEditLog() throws IOException {
+    testNameNodeRecoveryImpl(new SafePaddingCorruptor((byte)-1), true);
+    testNameNodeRecoveryImpl(new SafePaddingCorruptor((byte)-1), false);
+  }
 }



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