Using derived attributes in same processor in Apache Nifi

Question

I am adding two attributes in update attribute in which one depends on the other.
For example: say I create an attribute a = "Hello" and another attribute b=${a}.
Then the value of "b" is set to an empty string.
Is there any way in Nifi to use the value of "a" in the same processor or do I always need to create a new processor to use it?

Answer 1

Currently each UpdateAttribute property is evaluated independently of every other configured property (on the same processor). So in order to use "a" to create another property "b", you'd need to add a second UpdateAttribute processor.