We're using a Wait/Notify pattern in one of our flows to overcome a race condition problem (object x is referencing object y, object x will wait until object y is created. Creation of object y will generate the notification).
This basically works for most of our flow files. Files are waiting in queue and are released when notified as expected. However, for some flow files the notify- signal for object y is sent but object x will still be stuck in waiting state, not reacting on it.
I have enabled persistence on the cache and verified that the notify- signals are really added to it. I have juggled the different parameters of the wait/notify- processors without any success (it should require minimal configuration though since we only have a 1 to 1 relation between wait and notify signals).
We're using NiFi 1.6.0.