我是一个新用户,正在努力从ASP.NET Core Blazor服务器页面中优雅地关闭次要的signalR客户端。
我正在设置Blazor Server Page的第一次呈现上的次要signalR客户端连接。当通过浏览器标签关闭页面时,我试图关闭此次要的signalR客户端连接。
在撰写本文时,关闭页面时似乎不会触发DisposeAsync
。但是,Dispose
方法确实被触发。此外,在Safari 13.0.5中,关闭浏览器选项卡时Dispose
方法不会被触发?Opera、Firefox和Chrome在关闭浏览器选项卡时都会触发Dispose
。通过将Safari更新到v14.0 (15610.1.28.9, 15610)来解决这个问题,该更新通过macOS Catalina v10.15.7进行。
目前,我正在从Dispose
中调用DisposeAsync
以关闭signalR连接。我使用以下代码关闭客户端连接:
...
Logger.LogInformation("Closing secondary signalR connection...");
await hubConnection.StopAsync();
Logger.LogInformation("Closed secondary signalR connection");
...
StopAsync
方法似乎会阻塞,即 "Closed secondary signalR connection" 没有输出任何消息。虽然我的服务器端 hub 的 OnDisconnectedAsync
处理程序显示连接已经被断开。这类似于描述在这个 问题中所述的行为。如何在ASP.NET Core 3.1中正确处理 signalR 连接?
完整代码清单如下: 处理 signalR 连接关闭
#region Dispose
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
/// <summary>
/// Clear secondary signalR Closed event handler and stop the
/// secondary signalR connection
/// </summary>
/// <remarks>
/// ASP.NET Core Release Candidate 5 calls DisposeAsync when
/// navigating away from a Blazor Server page. Until the
/// release is stable DisposeAsync will have to be triggered from
/// Dispose. Sadly, this means having to use GetAwaiter().GetResult()
/// in Dispose().
/// However, providing DisposeAsync() now makes the migration easier
/// https://github.com/dotnet/aspnetcore/issues/26737
/// https://github.com/dotnet/aspnetcore/issues/9960
/// https://github.com/dotnet/aspnetcore/milestone/57?closed=1
/// </remarks>
protected virtual void Dispose(bool disposing)
{
if (disposed)
return;
if (disposing)
{
Logger.LogInformation("Index.razor page is disposing...");
try
{
if (hubConnection != null)
{
Logger.LogInformation("Removing signalR client event handlers...");
hubConnection.Closed -= CloseHandler;
}
// Until ASP.NET Core 5 is released in November
// trigger DisposeAsync(). See docstring and DiposeAsync() below.
// not ideal, but having to use GetAwaiter().GetResult() until
// forthcoming release of ASP.NET Core 5 for the introduction
// of triggering DisposeAsync on pages that implement IAsyncDisposable
DisposeAsync().GetAwaiter().GetResult();
}
catch (Exception exception)
{
Logger.LogError($"Exception encountered while disposing Index.razor page :: {exception.Message}");
}
}
disposed = true;
}
/// <summary>
/// Dispose the secondary backend signalR connection
/// </summary>
/// <remarks>
/// ASP.NET Core Release Candidate 5 adds DisposeAsync when
/// navigating away from a Blazor Server page. Until the
/// release is stable DisposeAsync will have to be triggered from
/// Dispose. Sadly, this means having to use GetAwaiter().GetResult()
/// in Dispose().
/// However, providing DisposeAsync() now makes the migration easier
/// https://github.com/dotnet/aspnetcore/issues/26737
/// https://github.com/dotnet/aspnetcore/issues/9960
/// https://github.com/dotnet/aspnetcore/milestone/57?closed=1
/// </remarks>
public async virtual ValueTask DisposeAsync()
{
try
{
if (hubConnection != null)
{
Logger.LogInformation("Closing secondary signalR connection...");
await hubConnection.StopAsync();
Logger.LogInformation("Closed secondary signalR connection");
}
// Dispose(); When migrated to ASP.NET Core 5 let DisposeAsync trigger Dispose
}
catch (Exception exception)
{
Logger.LogInformation($"Exception encountered wwhile stopping secondary signalR connection :: {exception.Message}");
}
}
#endregion
Blazor 服务器页面的完整代码
using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.SignalR.Client;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using WebApp.Data;
using WebApp.Data.Serializers.Converters;
using WebApp.Data.Serializers.Converters.Visitors;
using WebApp.Repository.Contracts;
namespace WebApp.Pages
{
public partial class Index : IAsyncDisposable, IDisposable
{
private HubConnection hubConnection;
public bool IsConnected => hubConnection.State == HubConnectionState.Connected;
private bool disposed = false;
[Inject]
public NavigationManager NavigationManager { get; set; }
[Inject]
public IMotionDetectionRepository Repository { get; set; }
[Inject]
public ILogger<MotionDetectionConverter> LoggerMotionDetection { get; set; }
[Inject]
public ILogger<MotionInfoConverter> LoggerMotionInfo { get; set; }
[Inject]
public ILogger<JsonVisitor> LoggerJsonVisitor { get; set; }
[Inject]
public ILogger<Index> Logger { get; set; }
#region Dispose
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
/// <summary>
/// Clear secondary signalR Closed event handler and stop the
/// secondary signalR connection
/// </summary>
/// <remarks>
/// ASP.NET Core Release Candidate 5 calls DisposeAsync when
/// navigating away from a Blazor Server page. Until the
/// release is stable DisposeAsync will have to be triggered from
/// Dispose. Sadly, this means having to use GetAwaiter().GetResult()
/// in Dispose().
/// However, providing DisposeAsync() now makes the migration easier
/// https://github.com/dotnet/aspnetcore/issues/26737
/// https://github.com/dotnet/aspnetcore/issues/9960
/// https://github.com/dotnet/aspnetcore/milestone/57?closed=1
/// </remarks>
protected virtual void Dispose(bool disposing)
{
if (disposed)
return;
if (disposing)
{
Logger.LogInformation("Index.razor page is disposing...");
try
{
if (hubConnection != null)
{
Logger.LogInformation("Removing signalR client event handlers...");
hubConnection.Closed -= CloseHandler;
}
// Until ASP.NET Core 5 is released in November
// trigger DisposeAsync(). See docstring and DiposeAsync() below.
// not ideal, but having to use GetAwaiter().GetResult() until
// forthcoming release of ASP.NET Core 5 for the introduction
// of triggering DisposeAsync on pages that implement IAsyncDisposable
DisposeAsync().GetAwaiter().GetResult();
}
catch (Exception exception)
{
Logger.LogError($"Exception encountered while disposing Index.razor page :: {exception.Message}");
}
}
disposed = true;
}
/// <summary>
/// Dispose the secondary backend signalR connection
/// </summary>
/// <remarks>
/// ASP.NET Core Release Candidate 5 adds DisposeAsync when
/// navigating away from a Blazor Server page. Until the
/// release is stable DisposeAsync will have to be triggered from
/// Dispose. Sadly, this means having to use GetAwaiter().GetResult()
/// in Dispose().
/// However, providing DisposeAsync() now makes the migration easier
/// https://github.com/dotnet/aspnetcore/issues/26737
/// https://github.com/dotnet/aspnetcore/issues/9960
/// https://github.com/dotnet/aspnetcore/milestone/57?closed=1
/// </remarks>
public async virtual ValueTask DisposeAsync()
{
try
{
if (hubConnection != null)
{
Logger.LogInformation("Closing secondary signalR connection...");
await hubConnection.StopAsync();
Logger.LogInformation("Closed secondary signalR connection");
}
// Dispose(); When migrated to ASP.NET Core 5 let DisposeAsync trigger Dispose
}
catch (Exception exception)
{
Logger.LogInformation($"Exception encountered wwhile stopping secondary signalR connection :: {exception.Message}");
}
}
#endregion
#region ComponentBase
/// <summary>
/// Connect to the secondary signalR hub after rendering.
/// Perform on the first render.
/// </summary>
/// <remarks>
/// This could have been performed in OnInitializedAsync but
/// that method gets executed twice when server prerendering is used.
/// </remarks>
protected override async Task OnAfterRenderAsync(bool firstRender)
{
if (firstRender)
{
var hubUrl = NavigationManager.BaseUri.TrimEnd('/') + "/motionhub";
try
{
Logger.LogInformation("Index.razor page is performing initial render, connecting to secondary signalR hub");
hubConnection = new HubConnectionBuilder()
.WithUrl(hubUrl)
.ConfigureLogging(logging =>
{
logging.AddConsole();
logging.AddFilter("Microsoft.AspNetCore.SignalR", LogLevel.Information);
})
.AddJsonProtocol(options =>
{
options.PayloadSerializerOptions = JsonConvertersFactory.CreateDefaultJsonConverters(LoggerMotionDetection, LoggerMotionInfo, LoggerJsonVisitor);
})
.Build();
hubConnection.On<MotionDetection>("ReceiveMotionDetection", ReceiveMessage);
hubConnection.Closed += CloseHandler;
Logger.LogInformation("Starting HubConnection");
await hubConnection.StartAsync();
Logger.LogInformation("Index Razor Page initialised, listening on signalR hub url => " + hubUrl.ToString());
}
catch (Exception e)
{
Logger.LogError(e, "Encountered exception => " + e);
}
}
}
protected override async Task OnInitializedAsync()
{
await Task.CompletedTask;
}
#endregion
#region signalR
/// <summary>Log signalR connection closing</summary>
/// <param name="exception">
/// If an exception occurred while closing then this argument describes the exception
/// If the signaR connection was closed intentionally by client or server, then this
/// argument is null
/// </param>
private Task CloseHandler(Exception exception)
{
if (exception == null)
{
Logger.LogInformation("signalR client connection closed");
}
else
{
Logger.LogInformation($"signalR client closed due to error => {exception.Message}");
}
return Task.CompletedTask;
}
/// <summary>
/// Add motion detection notification to repository
/// </summary>
/// <param name="message">Motion detection received via signalR</param>
private void ReceiveMessage(MotionDetection message)
{
try
{
Logger.LogInformation("Motion detection message received");
Repository.AddItem(message);
StateHasChanged();
}
catch (Exception ex)
{
Logger.LogError(ex, "An exception was encountered => " + ex.ToString());
}
}
#endregion
}
}
signalR 服务器端 Hub
using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.SignalR;
using Microsoft.Extensions.Logging;
namespace WebApp.Realtime.SignalR
{
/// <summary>
/// This represents endpoints available on the server, available for the
/// clients to call
/// </summary>
public class MotionHub : Hub<IMotion>
{
private bool _disposed = false;
public ILogger<MotionHub> Logger { get; set; }
public MotionHub(ILogger<MotionHub> logger) : base()
{
Logger = logger;
}
public override async Task OnConnectedAsync()
{
Logger.LogInformation($"OnConnectedAsync => Connection ID={Context.ConnectionId} : User={Context.User.Identity.Name}");
await base.OnConnectedAsync();
}
public override async Task OnDisconnectedAsync(Exception exception)
{
if (exception != null)
{
Logger.LogInformation($"OnDisconnectedAsync => Connection ID={Context.ConnectionId} : User={Context.User.Identity.Name} : Exception={exception.Message}");
}
else
{
Logger.LogInformation($"OnDisconnectedAsync => Connection ID={Context.ConnectionId} : User={Context.User.Identity.Name}");
}
await base.OnDisconnectedAsync(exception);
}
// Protected implementation of Dispose pattern.
protected override void Dispose(bool disposing)
{
if (_disposed)
{
return;
}
_disposed = true;
// Call base class implementation.
base.Dispose(disposing);
}
}
}
try{ await hubConnection.StopAsync(); } catch (Exception exception) { Logger.LogInformation(exception.Message);} finally { await hubConnection.DisposeAsync();}
。 - Zhi LvhubConnection.StopAsync()
周围放置异常处理块。 没有抛出异常。 看起来它在StopAsync
上被阻塞。 在Github Discussions上 提问 后,在Dispose
方法内将DisposeAsync().GetAwaiter().GetResult();
更改为_ = DisposeAsync()
,它可以工作了。 不确定为什么? 等待在GitHub上的跟进答案。 - anon_dcs3spp