[jira] [Commented] (HDFS-6500) Snapshot shouldn't be removed silently after renaming to an existing snapshot

[Yongjun Zhang (JIRA)]

    [ 
https://issues.apache.org/jira/browse/HDFS-6500?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14020842#comment-14020842
 ] 

Yongjun Zhang commented on HDFS-6500:
-------------------------------------

Hi [~djp], 

Thanks for finding and reporting the issue. I did a quick check at the source 
code level, it seems to be doing the checking for existing snapshot.
I wonder if you saw any exception from the following code. 

INodeDirectorySnapshottable.java:
{code}
  public void renameSnapshot(String path, String oldName, String newName)
      throws SnapshotException {
    if (newName.equals(oldName)) {
      return;
    }
    final int indexOfOld = searchSnapshot(DFSUtil.string2Bytes(oldName));
    if (indexOfOld < 0) {
      throw new SnapshotException("The snapshot " + oldName
          + " does not exist for directory " + path);
    } else {
      final byte[] newNameBytes = DFSUtil.string2Bytes(newName);
      int indexOfNew = searchSnapshot(newNameBytes);
      if (indexOfNew > 0) {
        throw new SnapshotException("The snapshot " + newName
            + " already exists for directory " + path);
      }
{code}

Thanks.


> Snapshot shouldn't be removed silently after renaming to an existing snapshot
> -----------------------------------------------------------------------------
>
>                 Key: HDFS-6500
>                 URL: https://issues.apache.org/jira/browse/HDFS-6500
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: snapshots
>    Affects Versions: 2.4.0
>            Reporter: Junping Du
>            Priority: Blocker
>
> Assume you have two snapshots for /dir: s1, s2, when you do "hdfs dfs 
> -renameSnapshot /dir s2 s1" which means you want to rename s2 to s1. It will 
> cause s2 been dropped silently and s1 still keep the previous one. This is 
> very confusing and easily cause wrong operation.
> The right behavior should be providing a warning to remind user that the 
> target name is already existed and do nothing. If user do want to overlap s1, 
> he should add some option (i.e. "-f") or delete s1 first.



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