How to receive data correctly and how to close normally

[dannyshenl]

I have a few questions when using BedrockFramework:

1. After the connection is established, is there a better way to read data except through a while true loop?

2. When I call _server.StopAsync() method, an exception will be thrown .

I guess the reason is that the connection is closed, but the reader.ReadAsync() method is still trying to read. How can I normally close the server. this is error detail:

    dbug: Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets[7]
        Connection id "0HMI96D1VNMLB" sending FIN because: "The connection was aborted by the application via ConnectionCo
    ntext.Abort()."
    fail: Athena.RPC.Transport.Bedrock.BedrockConnectionHandler[0]
        地址：[192.168.2.58:15023]已断开链接！
    fail: Athena.RPC.Transport.Bedrock.BedrockConnectionHandler[0]
        The connection was aborted by the application via ConnectionContext.Abort().
        Microsoft.AspNetCore.Connections.ConnectionAbortedException: The connection was aborted by the application via Con
    nectionContext.Abort().
            at System.IO.Pipelines.Pipe.GetReadResult(ReadResult& result)
            at System.IO.Pipelines.Pipe.GetReadAsyncResult()
            at System.IO.Pipelines.Pipe.DefaultPipeReader.GetResult(Int16 token)
            at Bedrock.Framework.Protocols.ProtocolReader.ContinueDoAsyncRead[TReadMessage](ValueTask`1 readTask, Nullable`
    1 maximumMessageSize, IMessageReader`1 reader, CancellationToken cancellationToken)
            at Athena.RPC.Transport.Bedrock.BedrockConnectionHandler.OnConnectedAsync(ConnectionContext connection) in D:\i
    afc_gitlab\mythology\code_net6\Athena.RPC.Transport.Bedrock\BedrockConnectionHandler.cs:line 84 

this is my source code:

using Bedrock.Framework.Protocols;
using Microsoft.AspNetCore.Connections;
using Microsoft.Extensions.Logging;
using System;
using System.Buffers;
using System.Collections.Concurrent;
using System.Net.Sockets;
using System.Threading;
using System.Threading.Tasks;
namespace Athena.RPC.Transport.Bedrock
{
    using Codec;
    using Protocols;
    using Runtime.Server;
    using Tracing;
    public class BedrockConnectionHandler : ConnectionHandler
    {
        private const int _acceptExceptionCount = 30;
        private const int _exceptionMonitorPeriod = 60000;

        private readonly IRpcMessageCodecFactory _rpcMessageCodecFactory;
        private readonly IRpcMessageEncoder _rpcMessageEncoder;
        private readonly IRpcMessageDecoder _rpcMessageDecoder;
        private readonly ITransportListener _transportListener;
        private readonly IServiceHealthCheck _serviceHealthCheck;
        private readonly IEventTracer _eventTracer;
        private readonly Timer _timerExceptionMonitor;
        private readonly ILogger _logger;

        private readonly ConcurrentDictionary<string, int> _exceptionCount;

        public BedrockConnectionHandler(IRpcMessageCodecFactory rpcMessageCodecFactory, ITransportListener transportListener, IServiceHealthCheck serviceHealthCheck, IEventTracer eventTracer, ILogger<BedrockConnectionHandler> logger)
        {
            _rpcMessageCodecFactory = rpcMessageCodecFactory;
            _rpcMessageDecoder = _rpcMessageCodecFactory.CreateDecoder();
            _rpcMessageEncoder = _rpcMessageCodecFactory.CreateEncoder();
            _transportListener = transportListener;
            _serviceHealthCheck = serviceHealthCheck;
            _eventTracer = eventTracer;
            _logger = logger;
            _exceptionCount = new ConcurrentDictionary<string, int>();
            _timerExceptionMonitor = new Timer(ExceptionCountClear, null, _exceptionMonitorPeriod, _exceptionMonitorPeriod);
        }

        private void ExceptionCountClear(object obj)
        {
            _exceptionCount.Clear();
            _logger.LogDebug("完成错误计数器数值清理");
        }

        public override async Task OnConnectedAsync(ConnectionContext connection)
        {
            var ipInfo = connection.RemoteEndPoint.ToString().Split(':');
            if (_serviceHealthCheck.IsHealthCheck(ipInfo[0], int.Parse(ipInfo[1])))
            {
                return;
            }
            var protocol = new LengthPrefixedProtocol();
            var reader = connection.CreateReader();
            var writer = connection.CreateWriter();
            if (_logger.IsEnabled(LogLevel.Information))
            {
                _logger.LogInformation("地址：[{RemoteEndPoint}]已建立链接！", connection.RemoteEndPoint);
            }
            var token = connection.ConnectionClosed.Register(() =>
            {
                DisposeConnection(connection, reader, writer).ConfigureAwait(false);
            });

            while (true)
            {
                if (token.Token.IsCancellationRequested)
                {
                    break;
                }
                try
                {
                    if (reader != null)
                    {
                        ProtocolReadResult<ReadOnlySequence<byte>> protocolReadResult;
                        try
                        {
                            protocolReadResult = await reader.ReadAsync(protocol, token.Token);
                        }
                        catch (InvalidOperationException connectionResetException)
                        {
                            _logger.LogError($"心跳地址未过滤，读取内容失败:{connectionResetException.Message} ");
                            break;
                        }
                        if (protocolReadResult.Message.Length > 0)
                        {
                            var rpcTransportMessage = _rpcMessageDecoder.MessageDecoding(protocolReadResult.Message);

                            var bedrockMessageSender = new BedrockMessageServiceSender(writer, _rpcMessageEncoder, _eventTracer, _logger);
                            if (_logger.IsEnabled(LogLevel.Information))
                            {
                                _logger.LogInformation("序列化数据成功，触发transport监听; 执行：{CorrelationId}", rpcTransportMessage.InvokeMessage.CorrelationId);
                            }
                            _eventTracer.CallReceiveEnd(this, new AthenaTraceEventArgs() { TransportMessage = rpcTransportMessage });
                            _transportListener.OnReceived(bedrockMessageSender, rpcTransportMessage);
                            reader?.Advance();
                        }
                        else
                        {
                            _logger.LogError("心跳地址未过滤，接收到空包将断开连接!");
                            break;
                        }
                    }
                }
                catch (ConnectionResetException connectionResetException)
                {
                    if (connectionResetException.InnerException is SocketException socketException)
                    {
                        if (socketException.SocketErrorCode == SocketError.ConnectionReset)
                        {
                            break;
                        }
                    }
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, ex.Message);
                    var key = $"{ex.GetType().Name}_{ex.Message}";
                    _exceptionCount.TryGetValue(key, out var errCount);
                    errCount++;
                    if (errCount > _acceptExceptionCount)
                    {
                        _logger.LogError($"链接：{connection.ConnectionId} 单位时间内出现异常超过阈值，将主动进行断开操作");
                        break;
                    }
                    else
                    {
                        _exceptionCount.TryUpdate(key, errCount, errCount);
                    }
                }
            }
        }

        public async Task DisposeConnection(ConnectionContext connection, ProtocolReader reader, ProtocolWriter writer)
        {
            if (reader != null && writer != null)
            {
                _logger.LogError("地址：[{RemoteEndPoint}]已断开链接！", connection.RemoteEndPoint);
                await reader.DisposeAsync();
                await writer.DisposeAsync();
                await connection.DisposeAsync();
            }
        }
    }
}

Thank you for your answer！

[adamradocz]

1. After the connection is established, is there a better way to read data except through a while true loop?

What's the matter with this approach?

[dannyshenl]

no problem I'm just curious if there are any other ways to use it

[adamradocz]

2. When I call _server.StopAsync() method, an exception will be thrown .

I just tried the sample server and it works fine. Can you elaborate on that?

[adamradocz]

BTW, you could check the token in the while instead of breaking it.

[dannyshenl]

BTW, you could check the token in the while instead of breaking it.

When should I break while ,if I didn't add if (token.Token.IsCancellationRequested) break; these codes,I will get an exception because the connection is closed, but the reader.ReadAsync() is still trying to read.

[adamradocz]

Pass the token to the reader.ReadAsync() as well.

[davidfowl]

This logic:

var token = connection.ConnectionClosed.Register(() =>
            {
                DisposeConnection(connection, reader, writer).ConfigureAwait(false);
            });

Is broken. Get rid of it. The system will dispose the connection and clean up when OnConnectedAsync unwinds.

When ProtocolReadResult\<T> has IsCompleted set then you know there's no more data coming. You can consume the existing messages and break the loop.

Everything else looks pretty normal.