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Update Network State Service

An implementation of the UpdateNetworkStateService will provide an object-oriented wrapper for the gRPC library, with the ability to update information about the state of the network. This is done with the following 3 steps:

  1. Create callbacks which will be called when gRPC messages are received from a client.
  2. Register the callbacks with an instance of the UpdateNetworkStateService.
  3. Add your UpdateNetworkStateService instance as a gRPC service.
info

The below examples make use of a helper library provided by Zepben, which is included as a transitive dependency of the SDK, or can be added directly from Maven Central.

You do NOT have to do this, you can register the services directly with a Netty gRPC (or other) server instead.

The classes you need for performing these actions can be imported from the SDK:

import com.zepben.evolve.conn.grpc.GrpcServer
import com.zepben.evolve.streaming.data.CurrentStateEvent
import com.zepben.evolve.streaming.data.SetCurrentStatesStatus
import com.zepben.evolve.streaming.mutations.UpdateNetworkStateService

Creating callbacks​

Each supported message in UpdateNetworkStateService requires a callback, which will be triggered when any client messages are received. Implementation of these callbacks can be done as either lambdas, or full method/function implementations that can be passed as method references.

onSetCurrentStates​

The onSetCurrentStates callback is triggered for each request passing in a batch of current state events, and should return a CompletableFuture of batch result response to reflect the success or failure of the update process.

// Using a lambda expression
var updateCurrentStatesLambda = { batchId: Long, events: List<CurrentStateEvent> ->
    // process updating of events here and return a CompletableFuture of batch result response
}

// Using a method
class UpdateNetworkStateServiceImpl {

    fun updateCurrentStates(batchId: Long, events: List<CurrentStateEvent>): CompletableFuture<SetCurrentStatesStatus> {
        // process updating of events here and return a CompletableFuture of batch result response
    }

}

Registering callbacks​

Registering the callbacks with the service is as simple as passing them into the UpdateNetworkStateService constructor.

// Using lambda expressions
val service = UpdateNetworkStateService(updateCurrentStatesLambda)

// Using method references
class UpdateNetworkStateServiceImpl {

    val service = UpdateNetworkStateService(::updateCurrentStates);

}

Registering the service​

For the above code to have any effect, you need to register the service with a gRPC server. Once this has been done, you should start to receive callbacks for each request sent from a gRPC client.

fun main() {
    val grpcServer = object : GrpcServer(9001) {
        init {
            serverBuilder.addService(service)
        }
    }
    grpcServer.start()
}

Putting it all together​

Putting each of the steps above together, you can build the scaffold of a working application

import com.zepben.evolve.conn.grpc.GrpcServer
import com.zepben.evolve.streaming.data.CurrentStateEvent
import com.zepben.evolve.streaming.mutations.UpdateNetworkStateService

fun main() {
    val service = UpdateNetworkStateService(onSetCurrentStates = { batchId: Long, events: List<CurrentStateEvent> ->
       // process updating of events here and return a CompletableFuture of batch result response
    })

    val grpcServer = object : GrpcServer(9001) {
        init {
            serverBuilder.addService(service)
        }
    }
    grpcServer.start()
}