Replace server Select loop with individual client threads.
This guarantees that any unexpected blocking calls due to network issues cannot stall the main server thread.
This commit is contained in:
Paul Chote
@@ -10,21 +10,22 @@
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#endregion
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using System;
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using System.Collections.Concurrent;
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using System.Collections.Generic;
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using System.Linq;
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using System.Net;
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using System.Net.Sockets;
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using System.Threading;
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namespace OpenRA.Server
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{
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public class Connection
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public class Connection : IDisposable
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{
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public const int MaxOrderLength = 131072;
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public readonly Socket Socket;
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public readonly List<byte> Data = new List<byte>();
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public readonly int PlayerIndex;
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public readonly string AuthToken;
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public readonly EndPoint EndPoint;
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public long TimeSinceLastResponse => Game.RunTime - lastReceivedTime;
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public int MostRecentFrame { get; private set; }
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@@ -32,130 +33,143 @@ namespace OpenRA.Server
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public bool TimeoutMessageShown;
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public bool Validated;
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ReceiveState state = ReceiveState.Header;
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int expectLength = 8;
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int frame = 0;
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long lastReceivedTime = 0;
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public Connection(Socket socket, int playerIndex, string authToken)
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readonly BlockingCollection<byte[]> sendQueue = new BlockingCollection<byte[]>();
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public Connection(Socket socket, int playerIndex, string authToken, Action<Connection, int, byte[]> onPacket, Action<Connection> onDisconnect)
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{
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Socket = socket;
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PlayerIndex = playerIndex;
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AuthToken = authToken;
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}
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EndPoint = socket.RemoteEndPoint;
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public byte[] PopBytes(int n)
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{
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var result = Data.GetRange(0, n);
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Data.RemoveRange(0, n);
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return result.ToArray();
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}
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bool ReadDataInner(Server server)
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{
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var rx = new byte[1024];
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var len = 0;
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while (true)
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new Thread(SendReceiveLoop)
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{
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try
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{
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// Poll the socket first to see if there's anything there.
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// This avoids the exception with SocketErrorCode == `SocketError.WouldBlock` thrown
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// from `socket.Receive(rx)`.
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if (!Socket.Poll(0, SelectMode.SelectRead)) break;
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if ((len = Socket.Receive(rx)) > 0)
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Data.AddRange(rx.Take(len));
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else
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{
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if (len == 0)
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server.DropClient(this);
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break;
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}
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}
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catch (SocketException e)
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{
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// This should no longer be needed with the socket.Poll call above.
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if (e.SocketErrorCode == SocketError.WouldBlock) break;
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server.DropClient(this);
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Log.Write("server", "Dropping client {0} because reading the data failed: {1}", PlayerIndex, e);
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return false;
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}
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}
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lastReceivedTime = Game.RunTime;
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TimeoutMessageShown = false;
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return true;
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Name = $"Client communication ({EndPoint}",
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IsBackground = true
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}.Start((socket, onPacket, onDisconnect));
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}
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public void ReadData(Server server)
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void SendReceiveLoop(object s)
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{
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if (ReadDataInner(server))
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var (socket, onPacket, onDisconnect) = (ValueTuple<Socket, Action<Connection, int, byte[]>, Action<Connection>>)s;
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socket.Blocking = false;
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socket.NoDelay = true;
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var receiveBuffer = new byte[1024];
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var readBuffer = new List<byte>();
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var state = ReceiveState.Header;
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var expectLength = 8;
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var frame = 0;
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try
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{
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while (Data.Count >= expectLength)
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while (true)
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{
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var bytes = PopBytes(expectLength);
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switch (state)
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// Wait up to 100ms for data to arrive before checking for data to send
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if (socket.Poll(100000, SelectMode.SelectRead))
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{
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case ReceiveState.Header:
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var read = socket.Receive(receiveBuffer);
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if (read == 0)
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{
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// Empty packet signals that the client has been dropped
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return;
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}
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if (read > 0)
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{
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readBuffer.AddRange(receiveBuffer.Take(read));
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lastReceivedTime = Game.RunTime;
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TimeoutMessageShown = false;
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}
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while (readBuffer.Count >= expectLength)
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{
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var bytes = readBuffer.GetRange(0, expectLength).ToArray();
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readBuffer.RemoveRange(0, expectLength);
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switch (state)
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{
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expectLength = BitConverter.ToInt32(bytes, 0) - 4;
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frame = BitConverter.ToInt32(bytes, 4);
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state = ReceiveState.Data;
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if (expectLength < 0 || expectLength > MaxOrderLength)
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case ReceiveState.Header:
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{
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server.DropClient(this);
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Log.Write("server", "Dropping client {0} for excessive order length = {1}", PlayerIndex, expectLength);
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return;
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expectLength = BitConverter.ToInt32(bytes, 0) - 4;
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frame = BitConverter.ToInt32(bytes, 4);
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state = ReceiveState.Data;
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if (expectLength < 0 || expectLength > MaxOrderLength)
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{
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Log.Write("server", $"Closing socket connection to {EndPoint} because of excessive order length: {expectLength}");
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return;
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}
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break;
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}
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break;
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}
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case ReceiveState.Data:
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{
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if (MostRecentFrame < frame)
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MostRecentFrame = frame;
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case ReceiveState.Data:
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onPacket(this, frame, bytes);
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expectLength = 8;
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state = ReceiveState.Header;
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break;
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}
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}
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}
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}
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// Client has been dropped by the server
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if (sendQueue.IsCompleted)
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return;
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// Send all data immediately, we will block again on read
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while (sendQueue.TryTake(out var data, 0))
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{
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var start = 0;
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var length = data.Length;
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// Non-blocking sends are free to send only part of the data
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while (start < length)
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{
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var sent = socket.Send(data, start, length - start, SocketFlags.None, out var error);
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if (error == SocketError.WouldBlock)
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{
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if (MostRecentFrame < frame)
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MostRecentFrame = frame;
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server.DispatchOrders(this, frame, bytes);
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expectLength = 8;
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state = ReceiveState.Header;
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break;
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Log.Write("server", "Non-blocking send of {0} bytes failed. Falling back to blocking send.", length - start);
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socket.Blocking = true;
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sent = socket.Send(data, start, length - start, SocketFlags.None);
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socket.Blocking = false;
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}
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else if (error != SocketError.Success)
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throw new SocketException((int)error);
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start += sent;
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}
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}
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}
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}
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catch (SocketException e)
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{
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Log.Write("server", $"Closing socket connection to {EndPoint} because of socket error: {e}");
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}
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finally
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{
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onDisconnect(this);
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socket.Dispose();
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}
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}
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public void SendData(byte[] data)
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{
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var start = 0;
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var length = data.Length;
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// Non-blocking sends are free to send only part of the data
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while (start < length)
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{
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var sent = Socket.Send(data, start, length - start, SocketFlags.None, out var error);
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if (error == SocketError.WouldBlock)
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{
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Log.Write("server", "Non-blocking send of {0} bytes failed. Falling back to blocking send.", length - start);
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Socket.Blocking = true;
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sent = Socket.Send(data, start, length - start, SocketFlags.None);
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Socket.Blocking = false;
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}
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else if (error != SocketError.Success)
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throw new SocketException((int)error);
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start += sent;
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}
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sendQueue.Add(data);
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}
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public EndPoint EndPoint => Socket.RemoteEndPoint;
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public void Dispose()
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{
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// Tell the sendReceiveThread that the socket should be closed
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sendQueue.CompleteAdding();
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}
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}
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public enum ReceiveState { Header, Data }
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