Github user joewitt commented on the issue:
https://github.com/apache/nifi/pull/2363
We should avoid the use of ThreadLocal storage completely. NiFi will not
give the same thread back to the same processor with any guarantees at all. So
we'd be caching/caching/caching and perhaps even leaking information across
threads like that. I think we should work the root cause angle with jolt---
