[jira] [Created] (HDFS-15059) Cache finalized replica info during datanode shutdown for fast restarting

["Yang Yun (Jira)" <ji...@apache.org>]

Yang Yun created HDFS-15059:
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             Summary: Cache finalized replica info during datanode shutdown for fast restarting
                 Key: HDFS-15059
                 URL: https://issues.apache.org/jira/browse/HDFS-15059
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: datanode
            Reporter: Yang Yun
            Assignee: Yang Yun


HDFS-7928 persist the whole volume map on the disk and let the datanode read that file and create the volume map during startup. This significantly improve the datanode startup time.
But it not works for any cases. For example, if datanode is killed, it's no chance to save the volume map.
Add a shutdown hook to make sure the volume map is saved during shutdown.
If the datanode is terminated by kill or other methods, we only reload the finalized replca from cache. It's is safe because the DirectoryScanner will run soon to correct possible missmatch.



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