Since Flink-1.5 you have the ability to set the part suffix.
As you said, you only want the .gzip to be the suffix of the final (or “completed”) part files, which is exactly what is currently supported.
If you want also intermediate files to have this suffix, then you can always set all the suffixes (in-progress, pending and final) to “.gzip”
but then you have to also set the appropriate preffixes so that Flink can distinguish completed from non-completed files (filenames
must not collide).
Also I would recommend to use the most recent stable version 1.5.3 which also includes this bug fix:https://issues.apache.org/jira/browse/FLINK-9603
I hope this helps,