Github user steveloughran commented on the issue:
https://github.com/apache/spark/pull/14731
Actually, I've just noticed that DStream behaviour isn't in sync with the
streaming programming guide, which says "files written in nested directories
not supported)". That is: SPARK-14796 didn't patch the docs.
it may as well be fixed in this patch. How about, in the bullet points
underneath
- Wildcards may be used to specify a set of directories to scan for new
files, for example `hdfs://nn1:8050/users/alice/logs/2016-*/*.gz`
-
-New directories and their contents will be discovered as they arrive
Special points for object stores
- Wildcard lookup may be very slow with some object stores.
- Directory rename is not atomic; if a directory is renamed into the
streaming source, then the files within may only be discovered and process
across a multiple streaming windows.
-
+ there's another optimisation; use the {{SparkHadoopUtils.isGlobPath()}}
predicate to recognise when the dir path isn't a wildcard, in which case just
do a simple listFiles()}}. Until that shortcutting is done automatically in the
Hadoop FS implementation, spark can do it on its side. As the {{listFiles()}}
call was what was used before SPARK-14796, it has to be compatible, else
SPARK-14796 has broken things
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