1.You can use Process group variables introduced in NiFi.1.4 instead of adding flowfile attributes and use the defined process group variables in your flow.
We cannot configure dynamic configurations per Node but for process group we can, by using process group variables.
if you define process group variables in particular process group(like FetchAndSaveFromHDFS) then the scope of variables will be in this process group.
Please refer to this link for more details regarding process group variables.
2.You can use Control rate processor to release a flowfile per certain amount of time(like for 1 min..) but this won't care about if the flowfile processing already finished or not, we are going to release flowfile per 1 min(or) Take a look on Wait and Notify processors keep your logic to wait until processing is done then release another flowfile.
This link demonstrates how to use Wait and Notify processors.
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