What's the meaning of 'processor' you defined here? A user defined function?
When talking about share state, I'm afraid it's not so easy to implement in Flink. As no matter keyed state or operator state, they're both instantiated, used and only thread-safe in operator scope. The only way to read read-only state during runtime is via
For the question of keyBy, the message would only sent to one of task in downstream according to the hashcode .