HDFS-6563. NameNode cannot save fsimage in certain circumstances when snapshots are in use. Contributed by Aaron T. Myers.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1603713 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -415,6 +415,9 @@ Release 2.5.0 - UNRELEASED
     HDFS-6553. Add missing DeprecationDeltas for NFS Kerberos configurations
     (Stephen Chu via brandonli)
 
+    HDFS-6563. NameNode cannot save fsimage in certain circumstances when
+    snapshots are in use. (atm)
+
   BREAKDOWN OF HDFS-2006 SUBTASKS AND RELATED JIRAS
 
     HDFS-6299. Protobuf for XAttr and client-side implementation. (Yi Liu via umamahesh)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatPBINode.java

@@ -530,9 +530,11 @@ public final class FSImageFormatPBINode {
       INodeSection.INodeFile.Builder b = buildINodeFile(n,
           parent.getSaverContext());
 
+      if (n.getBlocks() != null) {
         for (Block block : n.getBlocks()) {
           b.addBlocks(PBHelper.convert(block));
         }
+      }
 
       FileUnderConstructionFeature uc = n.getFileUnderConstructionFeature();
       if (uc != null) {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/FileWithSnapshotFeature.java

@@ -159,7 +159,7 @@ public class FileWithSnapshotFeature implements INode.Feature {
         // resize the array.  
         final BlockInfo[] newBlocks;
         if (n == 0) {
-          newBlocks = null;
+          newBlocks = BlockInfo.EMPTY_ARRAY;
         } else {
           newBlocks = new BlockInfo[n];
           System.arraycopy(oldBlocks, 0, newBlocks, 0, n);

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

@@ -28,12 +28,14 @@ import static org.junit.Assert.fail;
 import java.io.IOException;
 
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FSDataOutputStream;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
+import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockManager;
 import org.apache.hadoop.hdfs.server.namenode.FSDirectory;
@@ -396,4 +398,39 @@ public class TestSnapshotBlocksMap {
     assertEquals(1, blks.length);
     assertEquals(BLOCKSIZE, blks[0].getNumBytes());
   }
+  
+  /**
+   * Make sure that a delete of a non-zero-length file which results in a
+   * zero-length file in a snapshot works.
+   */
+  @Test
+  public void testDeletionOfLaterBlocksWithZeroSizeFirstBlock() throws Exception {
+    final Path foo = new Path("/foo");
+    final Path bar = new Path(foo, "bar");
+    final byte[] testData = "foo bar baz".getBytes();
+    
+    // Create a zero-length file.
+    DFSTestUtil.createFile(hdfs, bar, 0, REPLICATION, 0L);
+    assertEquals(0, fsdir.getINode4Write(bar.toString()).asFile().getBlocks().length);
+
+    // Create a snapshot that includes that file.
+    SnapshotTestHelper.createSnapshot(hdfs, foo, "s0");
+    
+    // Extend that file.
+    FSDataOutputStream out = hdfs.append(bar);
+    out.write(testData);
+    out.close();
+    INodeFile barNode = fsdir.getINode4Write(bar.toString()).asFile();
+    BlockInfo[] blks = barNode.getBlocks();
+    assertEquals(1, blks.length);
+    assertEquals(testData.length, blks[0].getNumBytes());
+    
+    // Delete the file.
+    hdfs.delete(bar, true);
+    
+    // Now make sure that the NN can still save an fsimage successfully.
+    cluster.getNameNode().getRpcServer().setSafeMode(
+        SafeModeAction.SAFEMODE_ENTER, false);
+    cluster.getNameNode().getRpcServer().saveNamespace();
+  }
 }