[jira] [Created] (HADOOP-14137) Allow DistCp to take a file list within a src directory

["Zheng Shao (JIRA)" <ji...@apache.org>]

Zheng Shao created HADOOP-14137:
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             Summary: Allow DistCp to take a file list within a src directory
                 Key: HADOOP-14137
                 URL: https://issues.apache.org/jira/browse/HADOOP-14137
             Project: Hadoop Common
          Issue Type: New Feature
          Components: tools/distcp
            Reporter: Zheng Shao


DistCp is very slow to start when the src directory has a huge number of subdirectories.  In our case, we already have the directory listing (via "hdfs oiv -i fsimage" or via nightly "hdfs dfs -lr -r /" dumps), and we would like to use that instead of doing realtime listing on the NameNode.

The "-f" option doesn't help in this case because it would try to put everything into a single flat target directory.

We'd like to introduce a new option "-list <file>" for distcp.  The <file> contains the result of listing the src directory.


In order to achieve this, we plan to:
1. Add a new CopyListing class PregeneratedCopyListing similar to SimpleCopyListing which doesn't "-ls -r" into the directory, but takes the listing via "-list"
2. Add an option "-list <file>" which will automatically make distcp use the new PregeneratedCopyListing class.




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