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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