Hi all：
In the `mapWithState` method in spark streaming, you need to pass in an
anonymous function. This function maintains a state and should return a
result. It can be said that the final stateful result can be obtained from the
state object.
So, what is the significance of returning result?
I looked up the official API, and it did not specifically say that the
result is used for, just give a simple explanation, as follows:
// A mapping function that maintains an integer state and return a String
def mappingFunction(key: String, value: Option[Int], state: State[Int]):
Option[String] = {
// Use state.exists(), state.get(), state.update() and state.remove()
// to manage state, and return the necessary string
}
val spec = StateSpec.function(mappingFunction).numPartitions(10)
val mapWithStateDStream = keyValueDStream.mapWithState[StateType,
MappedType](spec)
Can anyone help me with this problem?Thanks!
shicheng31...@gmail.com
