Github user zenfenan commented on the issue:
https://github.com/apache/nifi/pull/2436
@pvillard31 Actually I left `AtomicReference` on purpose. The reason was I
wanted to implement some features later that would need that but yeah it
doesn't concern or matter for the current commit/Jira so I took that off as
well as fixed to `@InputRequirement(Requirement.INPUT_REQUIRED)`---
