Adding Metrics to StreamingFileSink

[Kailash Dayanand-3]

Hello,

I was looking to add metrics to the streaming file sink. Currently the only
details available is the generic information about for any operator like
the number of records in, number of records out etc. I was looking at
adding some metrics and contributing back as well as enabling the metrics
which are already getting published by the aws-hadoop. Is that something
which is of value for the community?

Another change I am proposing is to make the constructor of
StreamingFileSink protected instead of private here:
https://tinyurl.com/y5vh4jn6. If we can make this as protected, then it is
possible to extend this class and have custom metrics for anyone to add in
the 'open' method.

Thanks
Kailash