[GitHub] spark pull request #14731: [SPARK-17159] [streaming]: optimise check for new...

[steveloughran <gi...@git.apache.org>]

Github user steveloughran commented on a diff in the pull request:

    https://github.com/apache/spark/pull/14731#discussion_r94407115
  
    --- Diff: docs/streaming-programming-guide.md ---
    @@ -644,17 +644,90 @@ methods for creating DStreams from files as input sources.
         </div>
         </div>
     
    -	Spark Streaming will monitor the directory `dataDirectory` and process any files created in that directory (files written in nested directories not supported). Note that
    +	Spark Streaming will monitor the directory `dataDirectory` and process any files created in that directory.
    +
    +     ++ The files must have the same data format.
    +     + A simple directory can be monitored, such as `hdfs://namenode:8040/logs/`.
    +       All files directly such a path will be processed as they are discovered.
    +     + A POSIX glob pattern can be supplied, such as
    +       `hdfs://namenode:8040/logs/2016-??-31`.
    +       Here, the DStream will consist of all files directly under those directories
    +       matching the regular expression.
    --- End diff --
    
    I added a link to the posix docs. If you follow them, you eventually end up on some coverage of regexps inside []; the Hadoop Glob code does actually convert the shell expression to a java regexp, then compile it in, so presumably should handle everything that the regexp engine (originally {{java.util.regexp}}, currently {{com.google.re2j}} can compile. That's too much detail and something that should really be covered in the Hadoop docs by someone.


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