部署Blazor应用至Azure Linux应用服务：随机WebSocket连接故障排查

问题现象 #

采用全InteractiveServer渲染模式的Blazor应用部署到Azure应用服务后，多次执行同一操作会突然触发控制台错误，刷新页面1-5次可恢复。错误信息如下：

Error: Failed to start the transport 'WebSockets': Error: WebSocket failed to connect. The connection could not be found on the server, either the endpoint may not be a SignalR endpoint, the connection ID is not present on the server, or there is a proxy blocking WebSockets. If you have multiple servers check that sticky sessions are enabled.
GET https://app-[removed]-001.azurewebsites.net/blazor?id=f9NSvVeKErKRUaRJWvmrfA&=1724694010721
Error: Failed to start the transport 'LongPolling': Error: No Connection with that ID: Status code '404'
Error: Failed to start the connection: Error: Unable to connect to the server with any of the available transports. Error: WebSockets failed: Error: WebSocket failed to connect. The connection could not be found on the server, either the endpoint may not be a SignalR endpoint, the connection ID is not present on the server, or there is a proxy blocking WebSockets. If you have multiple servers check that sticky sessions are enabled. ServerSentEvents failed: Error: 'ServerSentEvents' does not support Binary. Error: LongPolling failed: Error: No Connection with that ID: Status code '404'

应用配置信息 #

Program.cs代码 #

using HelpDesk.Components;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Azure;
using HelpDesk.Services;
using HelpDesk.Data;
using MudBlazor.Services;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddMudServices();
// Add services to the container.
builder.Services.AddRazorComponents()
    .AddInteractiveServerComponents();
builder.Services.AddDbContext<SpContext>(
    opt => opt.UseSqlServer(builder.Configuration.GetConnectionString("StoredProcedureUser")), ServiceLifetime.Transient);
builder.Services.AddAzureClients(ab => {
    ab.AddServiceBusClient(builder.Configuration["AzureWebJobsServiceBus"]);
});
builder.Services.AddTransient<IProceduresService, ProceduresService>();
builder.Services.AddTransient<ServiceBusService>();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error", createScopeForErrors: true);
    // 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.UseAntiforgery();

app.MapRazorComponents<App>()
    .AddInteractiveServerRenderMode();

app.Run();

.csproj文件内容 #

<PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <UserSecretsId>foo</UserSecretsId>
  </PropertyGroup>

  <PropertyGroup Condition=" '$(RunConfiguration)' == 'https' " />
  <PropertyGroup Condition=" '$(RunConfiguration)' == 'http' " />
  <ItemGroup>
    <PackageReference Include="Azure.Messaging.ServiceBus" Version="7.18.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="8.0.8" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="8.0.8" />
    <PackageReference Include="Microsoft.Extensions.Azure" Version="1.7.5" />
    <PackageReference Include="MudBlazor" Version="7.6.0" />
  </ItemGroup>

</Project>

已排查信息 #

• 应用服务计划为Basic级别，WebSocket连接数无限制
• 不确定是否必须使用SignalR

更新 #

发现GitHub上有一个Issue描述了完全相同的问题。

故障原因分析及解决方案 #

1. SignalR依赖确认
   Blazor InteractiveServer渲染模式必须依赖SignalR实现客户端与服务器的实时双向通信，所有交互都通过SignalR连接传递，是核心依赖，无法移除。

2. Azure应用服务配置调整

   • 开启粘性会话（ARR Affinity）：即使是单实例Basic计划，Azure应用服务的代理配置可能导致连接路由异常。进入Azure门户的应用服务 -> 设置 -> 配置 -> 常规设置，将"ARR Affinity"设为"开启"。
   • 确认WebSocket功能启用：进入应用服务 -> 设置 -> 配置 -> WebSocket，确保设置为"开启"。

3. 服务生命周期优化
   当前DbContext使用Transient生命周期，不符合EF Core的推荐最佳实践，可能导致不必要的实例创建和资源占用。建议改为Scoped：

builder.Services.AddDbContext<SpContext>(
    opt => opt.UseSqlServer(builder.Configuration.GetConnectionString("StoredProcedureUser")), ServiceLifetime.Scoped);

4. 框架版本更新
   当前使用ASP.NET Core 8.0.8，建议更新到最新的8.0.x补丁版本，修复框架层面可能存在的SignalR连接Bug。

5. 应用池回收检查
   查看Azure应用服务的应用池回收设置，避免频繁回收导致服务器端连接被强制中断，引发客户端旧连接ID失效问题。

内容的提问来源于stack exchange，提问作者Chris Rockwell