RetryPolicy does not work with coroutines

Question

I made a simple gRPC server in Kotlin with coroutines and a client with Java. In the cliente I enabled and configured a retry policy, but it does was not work. I speend a lot of time to find a solution, belivied that my client was broken, but the problem it was in the server. I will show you the code.

This is my proto file:

syntax = "proto3";
option java_multiple_files = true;
option java_package = "br.com.will.protoclasses";
option java_outer_classname = "NotificationProto";

package notification;

service Notification {
  rpc SendPush (SendPushNotificationRequest) returns (SendPushNotificationResponse);
}

message SendPushNotificationRequest {
  string title = 1;
  string message = 2;
  string customer_id = 3;
}

message SendPushNotificationResponse {
  string message = 1;
}

This is the client:

open class NotificationClient(private val channel: ManagedChannel) {
    private val stub: NotificationGrpcKt.NotificationCoroutineStub =
        NotificationGrpcKt.NotificationCoroutineStub(channel)

    suspend fun send() {
        val request =
            SendPushNotificationRequest.newBuilder().setCustomerId(UUID.randomUUID().toString()).setMessage("test")
                .setTitle("test").build()
        val response =  stub.sendPush(request)
        println("Received: ${response.message}")
    }

}

suspend fun main(args: Array<String>) {
    val port = System.getenv("PORT")?.toInt() ?: 50051

    val retryPolicy: MutableMap<String, Any> = HashMap()
    retryPolicy["maxAttempts"] = 5.0
    retryPolicy["initialBackoff"] = "10s"
    retryPolicy["maxBackoff"] = "30s"
    retryPolicy["backoffMultiplier"] = 2.0
    retryPolicy["retryableStatusCodes"] = listOf<Any>("INTERNAL")

    val methodConfig: MutableMap<String, Any> = HashMap()

    val name: MutableMap<String, Any> = HashMap()
    name["service"] = "notification.Notification"
    name["method"] = "SendPush"
    methodConfig["name"] = listOf<Any>(name)
    methodConfig["retryPolicy"] = retryPolicy

    val serviceConfig: MutableMap<String, Any> = HashMap()
    serviceConfig["methodConfig"] = listOf<Any>(methodConfig)

    print(serviceConfig)

    val channel = ManagedChannelBuilder.forAddress("localhost", port)
        .usePlaintext()
        .defaultServiceConfig(serviceConfig)
        .enableRetry()
        .build()

    val client = NotificationClient(channel)

    client.send()
}

This is a part of my gRPC service, where i was testing the retry policy (the retry policy on client does not work with this implementation):

override suspend fun sendPush(request: SendPushNotificationRequest): SendPushNotificationResponse {
    val count: Int = retryCounter.incrementAndGet()
    log.info("Received a call on method sendPushNotification with payload -> $request")

    if (random.nextFloat() < UNAVAILABLE_PERCENTAGE) {
        log.info("Returning stubbed INTERNAL error. count: $count")
        throw Status.INTERNAL.withDescription("error").asRuntimeException()
    }

    log.info("Returning successful Hello response, count: $count")
    return SendPushNotificationResponse.newBuilder().setMessage("success").build()

}

Another implementation, but now using StreamObserver (This implementation works fine):

override fun sendPush(
        request: SendPushNotificationRequest?,
        responseObserver: StreamObserver<SendPushNotificationResponse>?
    ) {
        log.info("Received a call on method sendPushNotification with payload -> $request")

        val count: Int = retryCounter.incrementAndGet()
        if (random.nextFloat() < UNAVAILABLE_PERCENTAGE) {
            log.info("Returning stubbed UNAVAILABLE error. count: $count")
            responseObserver!!.onError(
                Status.UNAVAILABLE.withDescription("error").asRuntimeException()
            )
        } else {
            log.info("Returning successful Hello response, count: $count")

            responseObserver!!.onNext(SendPushNotificationResponse.newBuilder().setMessage("success").build())
            return responseObserver.onCompleted()
        }
    }

The question is, whats is wrong? Can someone help me?

HelloWood · Accepted Answer · 2021-07-27 01:41:08Z

0

Does this code is generated by gRPC:

sendPush(request: SendPushNotificationRequest): SendPushNotificationResponse

gRPC depends on StreamObserver to send response to client after call responseObserver.onCompleted() or responseObserver.onError, please make sure your code could be work correctly.

answered Jul 27, 2021 at 1:41

HelloWood

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1 Comment

Cassiano Künsch das Neves Over a year ago

Yes, this code is generated by gRPC. I use the lib grpc-kotlin-stub, to generate this codes. I am using this implementation -> class NotificationGrpcService(private val notificationService: NotificationService) : NotificationGrpcKt.NotificationCoroutineImplBase()

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