Uploaded image for project: 'Hadoop Common'
  1. Hadoop Common
  2. HADOOP-12780

During WASB atomic rename handle crash when one directory has been renamed but not file under it.

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Critical
    • Resolution: Fixed
    • Affects Version/s: 2.8.0
    • Fix Version/s: 2.8.0, 3.0.0-alpha1
    • Component/s: fs/azure
    • Labels:
      None
    • Hadoop Flags:
      Reviewed

      Description

      During atomic folder rename process preperaion we record the proposed change to a metadata file (-renamePending.json).
      Say we are renaming parent/folderToRename to parent/renamedFolder.
      folderToRename has an inner folder innerFolder and innerFolder has a file innerFile
      Content of the –renamePending.json file will be

      { OldFolderName: parent/ folderToRename", NewFolderName: "parent/renamedFolder", FileList: [ "innerFolder", "innerFolder/innerFile" ] }

      Atfirst we rename all files within the source directory and then rename the source directory at the last step
      The steps are
      1. Atfirst we will rename innerFolder,
      2. Then rename innerFolder/innerFile
      3. Then rename source directory folderToRename
      Say the process crashes after step 1.
      So innerFolder has been renamed.
      Note that Azure storage does not natively support folder. So if a directory created by mkdir command, we create an empty placeholder blob with metadata for the directory.
      So after step 1, the empty blob corresponding to the directory innerFolder has been renamed.
      When the process comes up, in redo path it will go through the –renamePending.json file try to redo the renames.
      For each file in file list of renamePending file it checks if the source file exists, if source file exists then it renames the file. When it gets innerFolder, it calls filesystem.exists(innerFolder). Now filesystem.exists(innerFolder) will return true, because file under that folder exists even though the empty blob corresponding th that folder does not exist. So it will try to rename this folder, and as the empty blob has already been deleted so this fails with exception that “source blob does not exist”.

        Attachments

        1. HADOOP-12780.001.patch
          8 kB
          madhumita chakraborty

          Issue Links

            Activity

              People

              • Assignee:
                madhuch-ms madhumita chakraborty
                Reporter:
                madhuch-ms madhumita chakraborty
              • Votes:
                0 Vote for this issue
                Watchers:
                6 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved: