[jira] [Created] (HADOOP-12046) Avoid creating "._COPYING_" temporary file when copying file to Swift file system

["Chen He (JIRA)" <ji...@apache.org>]

Chen He created HADOOP-12046:
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             Summary: Avoid creating "._COPYING_" temporary file when copying file to Swift file system
                 Key: HADOOP-12046
                 URL: https://issues.apache.org/jira/browse/HADOOP-12046
             Project: Hadoop Common
          Issue Type: New Feature
    Affects Versions: 2.7.0
            Reporter: Chen He
            Assignee: Chen He


When copy file from HDFS or local to another file system implementation, in CommandWithDestination.java, it creates a temp file by adding suffix "._COPYING_". Once file is successfully copied, it will remove the suffix by rename(). 

try {
      PathData tempTarget = target.suffix("._COPYING_");
      targetFs.setWriteChecksum(writeChecksum);
      targetFs.writeStreamToFile(in, tempTarget, lazyPersist);
      targetFs.rename(tempTarget, target);
    } finally {
      targetFs.close(); // last ditch effort to ensure temp file is removed
    }

It is not costly in HDFS. However, if copy to Swift file system, the rename process is to create a new file. It is not efficient if users copy a lot of files to swift file system. I did some tests, for a 1G file copying to swift, it will take 10% more time. We should only do the copy one time for Swift file system. Changes should be limited to the Swift driver level.



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