Blazor Server在Firefox中偶现WebSocket未处于OPEN状态错误

问题现象 #

• 我们开发的基于.NET 7.0的Blazor Server应用部署在Windows Server 2019的IIS 10上，在最新版Chrome或Edge中运行正常，但部分使用最新版Firefox的用户会偶尔出现页面加载失败的情况，且使用时间越长，触发该问题的概率越高。
• 页面加载失败时，开发者控制台会出现以下错误：
  • Uncaught (in promise) WebSocket is not in the OPEN state
  • Uncaught (in promise) Error: cannot send data if the connection is not in the 'Connected' State.
• 偶尔在Chrome开发者控制台中会看到发送101 Switching Protocols请求，响应头包含Upgrade: websocket但状态码显示为200。不确定这是否意味着SignalR出现故障后，Chrome自动切换到“原生WebSocket”作为降级方案，而Firefox在尝试降级时失败。

已完成的排查操作 #

• 通过Firefox的about:config确认network.http.http2.websockets设置为true
• 重启过IIS服务器
• 确认IIS已安装WebSocket组件

背景与疑问 #

• 这是我们首个Blazor Server应用，对SignalR和WebSocket技术不熟悉，通过谷歌搜索及Stack Overflow查询均未找到相关解决方案。
• 我们的理解是应该使用SignalR（其底层基于WebSocket），而非微软所说的“原生WebSocket”。原本以为Blazor Server无需额外配置即可正常使用SignalR，但现在怀疑可能存在配置错误，导致应用一直依赖降级方案运行。

现有Program.cs代码 #

using Microsoft.EntityFrameworkCore;
using miniDARTS.Data;
using MudBlazor.Services;
using Microsoft.AspNetCore.Authentication.Negotiate;
using miniDARTS.Services;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();

// Blazor Server doesn't include HttpClient service by default.
builder.Services.AddHttpClient();

builder.Services.AddAuthentication(NegotiateDefaults.AuthenticationScheme).AddNegotiate();

builder.Services.AddAuthorization(options =>
{
    options.FallbackPolicy = options.DefaultPolicy;
});

// Configure the database connection.
string connectionString = "";

if (Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") == "Production")
{
    connectionString = builder.Configuration.GetConnectionString("miniDARTSContext");
}   

else if (Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") == "Development")
{
    connectionString = builder.Configuration.GetConnectionString("testing");
}

var serverVersion = new MySqlServerVersion(new Version(8, 0, 28));
builder.Services.AddDbContextFactory<miniDARTSContext>(options => options.UseMySql(connectionString, serverVersion), ServiceLifetime.Scoped);

// Only run cron jobs if they are in a production environment.
if (Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") == "Production")
{
    IHost host = Host.CreateDefaultBuilder(args)
        .ConfigureServices(services =>
        {
            services.AddHostedService<ScopedBackgroundService>();
            services.AddScoped<IScopedProcessingService, PhaseChangeReportService>();
        })
        .Build();

    host.RunAsync();
}

// Add MudBlazor services.
builder.Services.AddMudServices();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}

app.UseHttpsRedirection();

app.UseStaticFiles();

app.UseRouting();

app.UseAuthentication();
app.UseAuthorization();

app.UseEndpoints(endpoints =>
{
    endpoints.MapRazorPages();
});

app.MapBlazorHub();
app.MapFallbackToPage("/_Host");

app.Run();

内容的提问来源于stack exchange，提问作者Neil Wehneman