c#网络通信框架networkcomms内核解析之四 心跳检测

  protected static void TriggerConnectionKeepAliveThread()
        {
            lock (staticConnectionLocker)
            {
                if (!shutdownWorkerThreads && (connectionKeepAliveWorker == null || connectionKeepAliveWorker.ThreadState == ThreadState.Stopped))
                {
                    //创建一个新的线程，专门负责心跳检测
                    connectionKeepAliveWorker = new Thread(ConnectionKeepAliveWorker);
                    connectionKeepAliveWorker.Name = "ConnectionKeepAliveWorker";
                    connectionKeepAliveWorker.Start();
                }
            }
        }

  private static void ConnectionKeepAliveWorker()
        {
            if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Debug("Connection keep alive polling thread has started.");
            DateTime lastPollCheck = DateTime.Now;

            while (!shutdownWorkerThreads)
            {
                try
                {
                    //We have a short sleep here so that we can exit the thread fairly quickly if we need too
                    if (ConnectionKeepAlivePollIntervalSecs == int.MaxValue)
                        workedThreadSignal.WaitOne(5000);
                    else
                        workedThreadSignal.WaitOne(100);

                    //Check for shutdown here
                    if (shutdownWorkerThreads) break;

                    //Any connections which we have not seen in the last poll interval get tested using a null packet
                    if (ConnectionKeepAlivePollIntervalSecs < int.MaxValue && (DateTime.Now - lastPollCheck).TotalSeconds > (double)ConnectionKeepAlivePollIntervalSecs)
                    {
                        AllConnectionsSendNullPacketKeepAlive();
                        lastPollCheck = DateTime.Now;
                    }
                }
                catch (Exception ex)
                {
                    NetworkComms.LogError(ex, "ConnectionKeepAlivePollError");
                }
            }
        }

  /// <summary>
        /// Polls all existing connections based on ConnectionKeepAlivePollIntervalSecs value. Serverside connections are polled slightly earlier than client side to help reduce potential congestion.
        /// </summary>
        /// <param name="returnImmediately"></param>
        private static void AllConnectionsSendNullPacketKeepAlive(bool returnImmediately = false)
        {
            if (NetworkComms.LoggingEnabled) NetworkComms.Logger.Trace("Starting AllConnectionsSendNullPacketKeepAlive");

            //Loop through all connections and test the alive state
            List<Connection> allConnections = NetworkComms.GetExistingConnection();
            int remainingConnectionCount = allConnections.Count;

#if WINDOWS_PHONE
            QueueItemPriority nullSendPriority = QueueItemPriority.High;
#else
            QueueItemPriority nullSendPriority = QueueItemPriority.AboveNormal;
#endif

            ManualResetEvent allConnectionsComplete = new ManualResetEvent(false);
            for (int i = 0; i < allConnections.Count; i++)
            {
                //We don‘t send null packets to unconnected udp connections
                UDPConnection asUDP = allConnections[i] as UDPConnection;
                if (asUDP != null && asUDP.UDPOptions == UDPOptions.None)
                {
                    if (Interlocked.Decrement(ref remainingConnectionCount) == 0)
                        allConnectionsComplete.Set();

                    continue;
                }
                else
                {
                    int innerIndex = i;
                    NetworkComms.CommsThreadPool.EnqueueItem(nullSendPriority, new WaitCallback((obj) =>
                    {
                        try
                        {
                            //If the connection is server side we poll preferentially
                            if (allConnections[innerIndex] != null)
                            {
                                if (allConnections[innerIndex].ConnectionInfo.ServerSide)
                                {
                                    //We check the last incoming traffic time
                                    //In scenarios where the client is sending us lots of data there is no need to poll
                                    if ((DateTime.Now - allConnections[innerIndex].ConnectionInfo.LastTrafficTime).TotalSeconds > ConnectionKeepAlivePollIntervalSecs)
                                        allConnections[innerIndex].SendNullPacket();
                                }
                                else
                                {
                                    //If we are client side we wait upto an additional 3 seconds to do the poll
                                    //This means the server will probably beat us
                                       if ((DateTime.Now - allConnections[innerIndex].ConnectionInfo.LastTrafficTime).TotalSeconds > ConnectionKeepAlivePollIntervalSecs + 1.0 + (NetworkComms.randomGen.NextDouble() * 2.0))
                                        allConnections[innerIndex].SendNullPacket();
                                }
                            }
                        }
                        catch (Exception) { }
                        finally
                        {
                            if (Interlocked.Decrement(ref remainingConnectionCount) == 0)
                                allConnectionsComplete.Set();
                        }
                    }), null);
                }
            }

            //Max wait is 1 seconds per connection
            if (!returnImmediately && allConnections.Count > 0)
            {
                if (!allConnectionsComplete.WaitOne(allConnections.Count * 2500))
                    //This timeout should not really happen so we are going to log an error if it does
                    NetworkComms.LogError(new TimeoutException("Timeout after " + allConnections.Count.ToString() + " seconds waiting for null packet sends to finish. " + remainingConnectionCount.ToString() + " connection waits remain. This error indicates very high send load or a possible send deadlock."), "NullPacketKeepAliveTimeoutError");
            }
        }