Only one ServerStreamingCall can response when Clientconnection built on NIOTSEventLoopGroup

[foxsin10]

What are you trying to achieve?

Can't response multiple ServerStreamingCall when EventLoopGroup was set to NIOTSEventLoopGroup on a real device, while it woks fine on simulators

What have you tried so far?

I build an app on iOS platform, currently I have two services, first one using UnaryCall, second one use ServerStreamingCall works like socket.
Both services' channel was provided by ClientConnection, and PlatformSupport.makeEventLoopGroup(loopCount:) was used to provide EventLoopGroup, which use NIOTSEventLoopGroup by default.
Recently I need to build a new service, which use ServerStreamingCall to send and response message. when build the channel, MultiThreadedEventLoopGroup works fine on real devices, while NIOTSEventLoopGroup can't.

Any ideas will be appreciated. Thanks

[Lukasa]

When you say it doesn’t work, what does happen? Have you provisioned appropriate networking entitlements?

[foxsin10]

Under this code snippet, I can make multiple ServerStreamingCall , which are only one or two parameters are different.

let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
let configuration = ClientConnection.Configuration(target: .hostAndPort(host, port), eventLoopGroup: group, errorDelegate: self, connectivityStateDelegate: self)

And under this code snippet :

let group = PlatformSupport.makeEventLoopGroup(loopCount: 1)
let configuration = ClientConnection.Configuration(target: .hostAndPort(host, port), eventLoopGroup: group, errorDelegate: self, connectivityStateDelegate: self)

I can only get fufilled ServerStreamingCall once.

I want to know why

[Lukasa]

When you say once, you mean once per app launch? Once per device? Once per server?

[foxsin10]

No, Every time I present a viewcontroller, I can request once. The channel's lifecycle was binding to the controller.

[Lukasa]

Can you show the setup code from the view controller? How are you managing the grpc state there?

[foxsin10]

here is my code. I use an instance of ChartGrpcClient class in the viewcontroller.I deleted some code

final class ChartGrpcClient<T: Codable> {
    private var grpcClient: Grpc_Gateway_GateWayCallClient?
    private var channel: ClientConnection?
    
    private var channelQueue: DispatchQueue {
        return chartDataHandleQueue
    }
    
    private var grpcCall: ServerStreamingCall<Grpc_Gateway_GateWayRequest, Grpc_Gateway_GateWayResponse>?

    func send(_ request: Grpc_Gateway_GateWayRequest, completionHandler: @escaping (T) -> Void) {
        let handler: (Grpc_Gateway_GateWayResponse) -> Void = { (response) in
            if let data = response.playLoad.data(using: .utf8),
                let result = try? JSONDecoder().decode(T.self, from: data) {
                
                DispatchQueue.main.async {
                    completionHandler(result)
                }
                
            }
        }
        self.grpcCall = self.grpcClient?.request(
            request,
            callOptions: self.buildCallOptions(),
            handler: handler
        )
     }
    
     func buildConnection() {
        let channel = self.buildChannel()
        self.channel = channel
        self.bind(toChannel: channel)
     }
    
     private func bind(toChannel channel: GRPCChannel) {
        _ = self.grpcCall?.cancel()
        self.grpcClient = Grpc_Gateway_GateWayCallClient(channel: channel)
     }
    
     private func buildChannel() -> ClientConnection {
        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
        let configuration = ClientConnection.Configuration(
            target: .hostAndPort(host, port),
            eventLoopGroup: group,
            errorDelegate: self,
            connectivityStateDelegate: self
        )
        
        return ClientConnection(configuration: configuration)
     }
}

extension ChartGrpcClient: ClientErrorDelegate {
    func didCatchError(_ error: Error, logger: Logger, file: StaticString, line: Int) {}
}

extension ChartGrpcClient: ConnectivityStateDelegate {
    func connectivityStateDidChange(from oldState: ConnectivityState, to newState: ConnectivityState) {}
}

[Lukasa]

Ok, and how do you invoke this object in your view controller? What methods do you call?

[foxsin10]

call buildConnection() after viewDidload().
Then maybe tap a button to trigger send(_ : , completionHandler: ).
When the group is assigned with NIOTSEventLoopGroup, it will work once on real device, but I can send multiple requests and get responses on a simulator.
But if I assigned the group with MultiThreadedEventLoopGroup , I can send multiple requests and get responses

[foxsin10]

The object is a property of the viewcontroller.
The problem wasn't caused by the release of the object.

[Lukasa]

Can you print the logs from the connectivityStateDidChange in both cases?

[foxsin10]

Here, under NIOTSEventLoopGroup :

And, under MultiThreadedEventLoopGroup :

[Lukasa]

Ok, so POSIXErrorCode: Operation timed out is an error from Network.framework that indicates a timeout has occurred. This happened after the connection went live. It would be valuable to see how this interleaved with calls to send and the completionHandler: can you add those as well, please?

While we're here, you are also ignoring any errors that may be returned in handler. It would also be good to see if anything is appearing there.

[foxsin10]

There will be some changes to our Service, I will do some tests later.

[Lutzifer]

I have the same Issue:

self.group = PlatformSupport.makeEventLoopGroup(loopCount: 2) // Using this works on Simulator, but not on the device

self.group = MultiThreadedEventLoopGroup(numberOfThreads: 2) // This works on both Simulator and Device

Is there anything I can provide?