HDFS-6908. Incorrect snapshot directory diff generated by snapshot deletion. Contributed by Juan Yu and Jing Zhao.

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

@@ -642,6 +642,9 @@ Release 2.6.0 - UNRELEASED
 
     HDFS-4852. libhdfs documentation is out of date. (cnauroth)
 
+    HDFS-6908. Incorrect snapshot directory diff generated by snapshot deletion.
+    (Juan Yu and jing9 via jing9)
+
 Release 2.5.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

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

@@ -722,6 +722,8 @@ public class DirectoryWithSnapshotFeature implements INode.Feature {
         counts.add(lastDiff.diff.destroyCreatedList(currentINode,
             collectedBlocks, removedINodes));
       }
+      counts.add(currentINode.cleanSubtreeRecursively(snapshot, prior,
+          collectedBlocks, removedINodes, priorDeleted, countDiffChange));
     } else {
       // update prior
       prior = getDiffs().updatePrior(snapshot, prior);
@@ -739,7 +741,9 @@ public class DirectoryWithSnapshotFeature implements INode.Feature {
       
       counts.add(getDiffs().deleteSnapshotDiff(snapshot, prior,
           currentINode, collectedBlocks, removedINodes, countDiffChange));
-      
+      counts.add(currentINode.cleanSubtreeRecursively(snapshot, prior,
+          collectedBlocks, removedINodes, priorDeleted, countDiffChange));
+
       // check priorDiff again since it may be created during the diff deletion
       if (prior != Snapshot.NO_SNAPSHOT_ID) {
         DirectoryDiff priorDiff = this.getDiffs().getDiffById(prior);
@@ -778,9 +782,7 @@ public class DirectoryWithSnapshotFeature implements INode.Feature {
         }
       }
     }
-    counts.add(currentINode.cleanSubtreeRecursively(snapshot, prior,
-        collectedBlocks, removedINodes, priorDeleted, countDiffChange));
-    
+
     if (currentINode.isQuotaSet()) {
       currentINode.getDirectoryWithQuotaFeature().addSpaceConsumed2Cache(
           -counts.get(Quota.NAMESPACE), -counts.get(Quota.DISKSPACE));

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

@@ -19,6 +19,7 @@ package org.apache.hadoop.hdfs.server.namenode.snapshot;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -558,7 +559,81 @@ public class TestSnapshotDeletion {
           + toDeleteFileInSnapshot.toString(), e);
     }
   }
-  
+
+  /**
+   * Delete a snapshot that is taken before a directory deletion,
+   * directory diff list should be combined correctly.
+   */
+  @Test (timeout=60000)
+  public void testDeleteSnapshot1() throws Exception {
+    final Path root = new Path("/");
+
+    Path dir = new Path("/dir1");
+    Path file1 = new Path(dir, "file1");
+    DFSTestUtil.createFile(hdfs, file1, BLOCKSIZE, REPLICATION, seed);
+
+    hdfs.allowSnapshot(root);
+    hdfs.createSnapshot(root, "s1");
+
+    Path file2 = new Path(dir, "file2");
+    DFSTestUtil.createFile(hdfs, file2, BLOCKSIZE, REPLICATION, seed);
+
+    hdfs.createSnapshot(root, "s2");
+
+    // delete file
+    hdfs.delete(file1, true);
+    hdfs.delete(file2, true);
+
+    // delete directory
+    assertTrue(hdfs.delete(dir, false));
+
+    // delete second snapshot
+    hdfs.deleteSnapshot(root, "s2");
+
+    NameNodeAdapter.enterSafeMode(cluster.getNameNode(), false);
+    NameNodeAdapter.saveNamespace(cluster.getNameNode());
+
+    // restart NN
+    cluster.restartNameNodes();
+  }
+
+  /**
+   * Delete a snapshot that is taken before a directory deletion (recursively),
+   * directory diff list should be combined correctly.
+   */
+  @Test (timeout=60000)
+  public void testDeleteSnapshot2() throws Exception {
+    final Path root = new Path("/");
+
+    Path dir = new Path("/dir1");
+    Path file1 = new Path(dir, "file1");
+    DFSTestUtil.createFile(hdfs, file1, BLOCKSIZE, REPLICATION, seed);
+
+    hdfs.allowSnapshot(root);
+    hdfs.createSnapshot(root, "s1");
+
+    Path file2 = new Path(dir, "file2");
+    DFSTestUtil.createFile(hdfs, file2, BLOCKSIZE, REPLICATION, seed);
+    INodeFile file2Node = fsdir.getINode(file2.toString()).asFile();
+    long file2NodeId = file2Node.getId();
+
+    hdfs.createSnapshot(root, "s2");
+
+    // delete directory recursively
+    assertTrue(hdfs.delete(dir, true));
+    assertNotNull(fsdir.getInode(file2NodeId));
+
+    // delete second snapshot
+    hdfs.deleteSnapshot(root, "s2");
+    assertTrue(fsdir.getInode(file2NodeId) == null);
+
+    NameNodeAdapter.enterSafeMode(cluster.getNameNode(), false);
+    NameNodeAdapter.saveNamespace(cluster.getNameNode());
+
+    // restart NN
+    cluster.restartNameNodes();
+  }
+
   /**
    * Test deleting snapshots in a more complicated scenario: need to combine
    * snapshot diffs, but no need to handle diffs distributed in a dir tree