Message order is important. I am running a Nifi cluster that reads from a JMS queue. Then passes it along a flow that does more stuff.
So what happens during a fail-over? Node #1 reads messages 1-3, Node #2 has 4-6, Node #3 has 7-10. Node #1 goes down. Do Messages 1-3 get then get passed over to another node? What is the timing of this, etc?
Is there ever a case these messages would get processed out of order?
Regardless of a node going down, the nodes process data independently of each other. The data on the nodes is processed as quickly as possible and the nodes are unaware of data on other nodes.
There is no way currently to force a ordered processing of data across multiple nodes.