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From "Ashu Pachauri (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-18399) Files in a snapshot can go missing even after the snapshot is taken successfully
Date Mon, 17 Jul 2017 21:43:00 GMT
Ashu Pachauri created HBASE-18399:

             Summary: Files in a snapshot can go missing even after the snapshot is taken
                 Key: HBASE-18399
                 URL: https://issues.apache.org/jira/browse/HBASE-18399
             Project: HBase
          Issue Type: Sub-task
            Reporter: Ashu Pachauri

Files missing after the snapshot is taken (only applicable when the TTL for the TimeToLiveHFileCleaner
is small, like the default 5 mins)
    * SnapshotManifest#addRegion visits store_file_A, but is yet to write it to the manifest.
    * store_file_A is marked as compacted away and HFileArchiver moves the file to archive.
    * HFileCleaner comes in and sees the store_file_A in archive. It adds the file to the
list of files that might need to be cleaned up.
    * HFileCleaner's SnapshotHFileCleaner plugin is kicked in.
    * SnapshotFileCache#getUnreferencedFiles also says that store_file_A is unreferenced and
should be cleaned up (It has not yet been written to the manifest).
    * SnapshotHFileCleaner is still going through rest of the files in archive.
    * store_file_A reference is created and written to snapshot manifest.
    * Snapshot verification runs and sees the store_file_A is present in archive, and thus
the verification passes.
    * Now, the SnapshotHFileCleaner finishes and TimeToLiveHFileCleaner is triggered. If TTL
has passed since the store_file_A was moved to archive (SnapshotHFileCleaner could take easily
several minutes to go through rest of the files), the TimeToLiveHFileCleaner also marks the
file as deletable.
    * Since all cleaner plugins marked file as deletable, the store_file_A is deleted.

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