HDFS-4650. When passing two non-existing snapshot names to snapshotDiff, it returns success if the names are the same. Contributed by Jing Zhao

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2802@1476408 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt

@@ -312,3 +312,6 @@ Branch-2802 Snapshot (Unreleased)
   HDFS-4650. Fix a bug in FSDirectory and add more unit tests for rename with
   existence of snapshottable directories and snapshots.  (Jing Zhao via
   szetszwo)
+
+  HDFS-4650. When passing two non-existing snapshot names to snapshotDiff, it
+  returns success if the names are the same.  (Jing Zhao via szetszwo)

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

@@ -372,6 +372,10 @@ public class INodeDirectorySnapshottable extends INodeDirectoryWithSnapshot {
       throws SnapshotException {
     Snapshot fromSnapshot = getSnapshotByName(from);
     Snapshot toSnapshot = getSnapshotByName(to);
+    // if the start point is equal to the end point, return null
+    if (from.equals(to)) {
+      return null;
+    }
     SnapshotDiffInfo diffs = new SnapshotDiffInfo(this, fromSnapshot,
         toSnapshot);
     computeDiffRecursively(this, new ArrayList<byte[]>(), diffs);

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

@@ -289,10 +289,6 @@ public class SnapshotManager implements SnapshotStats {
       // both fromSnapshot and toSnapshot indicate the current tree
       return null;
     }
-    // if the start point is equal to the end point, return null
-    if (from.equals(to)) {
-      return null;
-    }
 
     // Find the source root directory path where the snapshots were taken.
     // All the check for path has been included in the valueOf method.

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

@@ -186,6 +186,16 @@ public class TestSnapshotDiffReport {
           "Directory is not a snapshottable directory: " + subsub1, e);
     }
     
+    final String invalidName = "invalid";
+    try {
+      hdfs.getSnapshotDiffReport(sub1, invalidName, invalidName);
+      fail("Expect exception when providing invalid snapshot name for diff report");
+    } catch (IOException e) {
+      GenericTestUtils.assertExceptionContains(
+          "Cannot find the snapshot of directory " + sub1 + " with name "
+              + invalidName, e);
+    }
+    
     // diff between the same snapshot
     SnapshotDiffReport report = hdfs.getSnapshotDiffReport(sub1, "s0", "s0");
     System.out.println(report);