Hi!
A global shared variable is not something that is offered by Flink right now. It is not part of the system, because it is not really part of the stream or state derived from individual streams. It is also quite hard to do efficiently and general purpose.
I see that it is a useful tool in several use cases. You would currently have to add that yourself, you can try and use something like Redis to hold shared state, or you can use an embedded Akka and CRDTs to have replicated state that syncs up across all nodes.
Greetings,
Stephan