HeartSaVioR edited a comment on issue #23782: [SPARK-26875][SS] Add an option 
on FileStreamSource to include modified files
URL: https://github.com/apache/spark/pull/23782#issuecomment-463866912
 
 
   Maybe @gaborgsomogyi is considering more than what it is as of now. 
Currently #22952 is implemented as synchronous approach, but @gaborgsomogyi had 
his voice to make archiving/deletion being async in #22952 (we talked about 
dealing with it in next TODO), and it's based on the assumption that we never 
process the file again even same file is added as new.
   
   When the option is turned on, it breaks assumption and things will get 
changed very differently - including race condition what @gaborgsomogyi is 
stated. When we hit by race condition It would produce unintended result (maybe 
worse scenario would be archive/delete a new file before processing).
   
   Not sure race condition occurs even archiving/deleting is synchronous. Race 
condition still occurs between Spark and FileSystem, but that's not Spark can 
control and Spark just should make its best to archive/delete faster before 
others overwrite/delete them.

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