Github user jtstorck commented on the issue:
https://github.com/apache/nifi/pull/3174
Thanks for taking a look at the PR, @joewitt. That warning is due to
accessing, via reflection, the `pid` method on the Process API, which was added
in Java 9. The code that does this was added by NIFI-5175, to allow NiFI built
on Java 1.8 to run on Java 9. There's a comment in the code detailing why the
use of reflection is necessary. Please see
https://github.com/apache/nifi/blob/master/nifi-bootstrap/src/main/java/org/apache/nifi/bootstrap/util/OSUtils.java#L111.
The warning is expected, and when we have a minimum requirement of Java 11,
we can refactor OSUtils, or probably remove the class entirely, since the
Process API (as of Java 9) provides a platform independent way to get a PID. I
don't think we'll need to have the methods in OSUtils for getting the PID based
on which platform on which NiFi is running.
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