问题
I am trying to use addGlobalStore on a Kafka DSL where a need to store few values that I will need global access for all my threads/instances.
My problem is that I need periodically to update these values inside my topology and make all running threads aware of the new values.
I initialized the global store through builder.addGlobalStore and using the init() function of a Processor that was used as the last argument on this function, but I cannot find a way to update the values inside the global store.
The next step on my Topology is a Transformer where I can get a hook through ```init()`` on the global Store and read the stored values but unfortunately I cannot updated them globally. I mean I can update the local copy for the running thread but other threads/instances cannot see the change.
I read somewhere that this cannot be done on Transformer, but even I use a Processor instead the issue remains
So, Is there a way to update globalStateStore on a Kafka DSL topology, and if so how is this possible ? Or in order to use global store do I need to use the low level processor API ?
回答1:
I initialized the global store through builder.addGlobalStore and using the init() function of a Processor that was used as the last argument on this function, but I cannot find a way to update the values inside the global store.
You cannot update a global store directly. Instead, you must update (= write a message to) the underlying topic of that global store.
回答2:
In case it fits your needs you probably could use GlobalKTable instead of GlobalStore
来源：https://stackoverflow.com/questions/56239980/write-to-globalstatestore-on-kafka-streams