I'm currently working on
PIG-3015 and am having trouble passing the UDFContextSignature to the store func. It looks like the store func on the head end is being set to a non-null value, but a null value is being passed to setStoreFuncUDFContextSignature on the back end. I'm opening this ticket to track this issue; I'll follow up with a reproducible test case when I have a clean one.
I suspect this problem occurs when running on a real cluster, but may not occur in the standard unit tests.