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I have some problem with NetMQ 4.0.0.1 on Mono 4.8 on Debian Wheezy.

Where Dealer socket is not sending any message until I won't stop calling it to send new message. When I will put Thread.Sleep( 1000 ) between creating a tasks with than everything is ok. I would like to admit that everything is working on Windows in .Net Framework 4.5 and on .Net Core 1.1 without any Thread.Sleep().

I have pattern like this: enter image description here

I have added debug messages and I can see that I am creating 100 REQ sockets in Tasks in a loop, and Router is getting requests in a queue, than is sending them trough Dealer, and nothing is happening on the other side of TCP until I will stop call send on REQ sockets. A simple Thread.Sleep() on every 5 tasks is working. It looks like a Poller bug, or Dealer bug, or I am making something wrong.

Here is a code of middle box:

public class CollectorDevice : IDisposable
{
    private NetMQPoller _poller;
    private RouterSocket _frontendSocket;
    private DealerSocket _backendSocket;
    private readonly string _backEndAddress;
    private readonly string _frontEndAddress;
    private readonly int _expectedFrameCount;
    private readonly ManualResetEvent _startSemaphore = new ManualResetEvent(false);
    private readonly Thread _localThread;
    private static Logger _logger = LogManager.GetCurrentClassLogger();

    /// <summary>
    /// Constructor
    /// </summary>
    /// <param name="backEndAddress"></param>
    /// <param name="frontEndAddress"></param>
    /// <param name="expectedFrameCount"></param>
    public CollectorDevice(string backEndAddress, string frontEndAddress, int expectedFrameCount)
    {
        _expectedFrameCount = expectedFrameCount;

        _backEndAddress = backEndAddress;
        _frontEndAddress = frontEndAddress;

        _localThread = new Thread(DoWork) { Name = "IPC Collector Device Thread" };
    }

    public void Start()
    {
        _localThread.Start();
        _startSemaphore.WaitOne();


    }

    public void Stop()
    {
        _poller.Stop();
    }

    #region Implementation of IDisposable

    public void Dispose()
    {
        Stop();
    }

    #endregion


    #region Private Methods
    private void DoWork()
    {
        try
        {
            using (_poller = new NetMQPoller())
            using (_frontendSocket = new RouterSocket(_frontEndAddress))
            using (_backendSocket = new DealerSocket(_backEndAddress))
            {
                _backendSocket.ReceiveReady += OnBackEndReady;
                _frontendSocket.ReceiveReady += OnFrontEndReady;


                _poller.Add(_frontendSocket);
                _poller.Add(_backendSocket);

                _startSemaphore.Set();

                _poller.Run();
            }
        }
        catch (Exception e)
        {
            _logger.Error(e);
        }
    }

    private void OnBackEndReady(object sender, NetMQSocketEventArgs e)
    {
        NetMQMessage message = _backendSocket.ReceiveMultipartMessage(_expectedFrameCount);
        _frontendSocket.SendMultipartMessage(message);
    }

    private void OnFrontEndReady(object sender, NetMQSocketEventArgs e)
    {
        NetMQMessage message = _frontendSocket.ReceiveMultipartMessage(_expectedFrameCount);
        _backendSocket.SendMultipartMessage(message);
    }

    #endregion
}

Here is a client side:

class Program
{
    private static Logger _logger = LogManager.GetCurrentClassLogger();


    private static void Main(string[] args)
    {
        Console.WriteLine("Client. Please enter message for server. Enter 'QUIT' to turn off server");
        Console.ReadKey();


        using (var collectorDevice = new CollectorDevice(">tcp://localhost:5556", "inproc://broker", 3))
        {
            collectorDevice.Start();

            List<Task> tasks = new List<Task>();
            for (int i = 0; i < 100; i++)
            {
                Console.WriteLine(i);
                int j = i;       
                Task t = Task.Factory.StartNew(() =>
                {
                    try
                    {
                        using (var req = new RequestSocket("inproc://broker"))
                        {
                            req.SendFrame(String.Format("Request client: {0} id: {1}", j, Task.CurrentId));
                            _logger.Debug(String.Format("Request client: {0} id: {1}", j, Task.CurrentId));
                            Console.WriteLine(String.Format("Request client: {0} id: {1}", j, Task.CurrentId));

                            string responseMessage = req.ReceiveFrameString();
                            _logger.Debug(String.Format("Response from server: {0} id: {1} message: {2}", j, Task.CurrentId, responseMessage));
                            Console.WriteLine(String.Format("Response from server: {0} id: {1} message: {2}", j, Task.CurrentId, responseMessage));
                        }
                    }
                    catch (Exception e)
                    {
                        Console.WriteLine(e);
                        _logger.Error(e);
                    }
                });
                tasks.Add(t);
                //Thread.Sleep (100);//<- This thread sleep is fixing problem?
            }

            Task.WaitAll(tasks.ToArray());
        }

    }
}

And server side:

class Program
{
    private static Logger _logger = LogManager.GetCurrentClassLogger();

    static void Main(string[] args)
    {
        try{
        using (var routerSocket = new RouterSocket("@tcp://*:5556"))
        {
            var poller = new NetMQPoller();
            routerSocket.ReceiveReady += RouterSocketOnReceiveReady;
            poller.Add(routerSocket);
            poller.Run();
        }
        }
        catch(Exception e) 
        {      
            Console.WriteLine (e);
        }

        Console.ReadKey ();
    }

    private static void RouterSocketOnReceiveReady(object sender, NetMQSocketEventArgs netMqSocketEventArgs)
    {
        NetMQMessage clientMessage = new NetMQMessage();
        bool result = netMqSocketEventArgs.Socket.TryReceiveMultipartMessage(new TimeSpan(0, 0, 0, 5),
            ref clientMessage, 5);

        if (result == false)
        {
            Console.WriteLine ("Something went wrong?!");
        }

        var address = clientMessage[0];
        var address2 = clientMessage[1];
        var clientMessageString = clientMessage[3].ConvertToString();

        //_logger.Debug("Message from client received: '{0}'", clientMessageString);
        Console.WriteLine (String.Format ("Message from client received: '{0}'", clientMessageString));

        netMqSocketEventArgs
            .Socket.SendMoreFrame(address.Buffer)
            .SendMoreFrame(address2.Buffer)
            .SendMoreFrameEmpty()
            .SendFrame("I have received your message");
    }
}

Anybody has any idea?

I was thinking that I am maybe using socket from different threads, so I have packed it into ThreadLocal structure, but it wasnt helped.Than I have read about some problems in unity with NetMQ so I have added 'AsyncIO.ForceDotNet.Force();' before every socket constructor call, and this wasnt helped too. Than I have updated my mono to 4.8 from 4.4 and it still looks the same.

I have checked that Thread.Sleep(100) between tasks is fixing problem. It is strange

bzyku
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  • Any chance you are using any socket from multiple threads? – somdoron Mar 29 '17 at 16:51
  • Also, can you share the code of the request socket? – somdoron Mar 29 '17 at 16:51
  • I have put socket into ThreadLocal structure to be sure that I am not making that mistake. I have added more code like You want. By the way, thanks for fast response – bzyku Mar 30 '17 at 05:43
  • I'm looking into this, just wand to figure out, if on the server side you block for ever (instead of 5 seconds timeout), do you get the messages eventually? – somdoron Mar 30 '17 at 09:37
  • I have changed TryReceiveMultipartMessage in Server to ReceiveMultipartMesssage, and still the same. Only Thread.Sleep(100) between Tasks is fixing problem – bzyku Mar 30 '17 at 10:12
  • I can confirm I can reproduce, can you check with older versions of Mono? – somdoron Mar 30 '17 at 13:37

1 Answers1

2

I tested the code, it does take a lot of time but eventually server receives all messages (takes around a minute).

The problem is the amount of threads, all async operation which should be completed on io completion ports thread takes a lot of time when there are 100 threads. I was able to reproduce it without NetMQ with following code

    public static void Main(string[] args)
    {
        ManualResetEvent resetEvent = new ManualResetEvent(false);

        List<Task> tasks = new List<Task>();

        for (int i = 0; i < 100; i++)
        {
            tasks.Add(Task.Run(() =>
            {
                resetEvent.WaitOne();
            }));
        }

        Thread.Sleep(100);

        Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        listener.Bind(new IPEndPoint(IPAddress.Any, 5556));
        listener.Listen(1);

        SocketAsyncEventArgs args1 = new SocketAsyncEventArgs();
        args1.Completed += (sender, eventArgs) =>
        {
            Console.WriteLine($"Accepted {args1.SocketError}");
            resetEvent.Set();
        };
        listener.AcceptAsync(args1);

        SocketAsyncEventArgs args2 = new SocketAsyncEventArgs();
        args2.RemoteEndPoint = new IPEndPoint(IPAddress.Loopback, 5556);
        args2.Completed += (sender, eventArgs) => Console.WriteLine("Connected");
        Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        client.ConnectAsync(args2);

        Task.WaitAll(tasks.ToArray());

        Console.WriteLine("all tasks completed");
    }

You can see that is also takes around a minute. With only 5 threads it completed immediately.

Anyway you might want to start less threads and/or reoort a bug in mono project.

somdoron
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  • Thanks, I will propably lower down max number of threads in threadpool in webserver to some sensible number – bzyku Mar 31 '17 at 07:03