Azure Function启动失败：未找到dotnet-isolated语言函数

错误日志 #

[2024-04-25T09:22:29.421Z] Found C:\Users\gdifronzo\source_C#\AE.Resp.Device.Sync\ AE.Resp.Device.Sync\AE.Resp.Device.Sync\AE.Resp.Device.Sync.csproj. Using for user secrets file configuration.
[2024-04-25T09:22:30.766Z] A host error has occurred during startup operation 'd5c1ddb1-1e25-406a-b64c-ef69bf086ab4'.
[2024-04-25T09:22:30.768Z] Microsoft.Azure.WebJobs.Script: Did not find functions with language [dotnet-isolated].
[2024-04-25T09:22:30.786Z] Failed to stop host instance '8db57ba1-9d37-44cd-a3d9-e6e01699e700'.
[2024-04-25T09:22:30.788Z] Microsoft.Azure.WebJobs.Host: The host has not yet started. Value cannot be null. (Parameter 'provider')

local.settings.json配置 #

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "FhirServerUrl": "https://xxxxxxxxxxxx.azurewebsites.net",
    "TimeTriggerSchedule": "0 */5 * * *",
    "MaximumExecutionTime": 21600,
    "MongoDbConnectionString": "mongodb+srv://xxxxxxxxxxx",
    "MongoDbThumbprint": "xxxxxxxx"
  }
}

核心代码 #

Program.cs #

IHostBuilder builder = new HostBuilder().ConfigureFunctionsWebApplication();

var configuration = new ConfigurationBuilder()
    .AddEnvironmentVariables()
    .AddJsonFile("local.settings.json", true, true)
    .Build();

X509Certificate2 mongoCertificate;
string mongoConnectionString = configuration.GetValue<string>("MongoDbConnectionString") ?? throw new CertificateNotFoundException("Unable to load configuration with key 'MongoDbConnectionString'");

try
{
  mongoCertificate = Utils.LoadCertificate(configuration.GetRequiredSection("MongoDbThumbprint").Value);
}
catch
{
  throw;
}

MongoDBService mongoDBService = new(mongoConnectionString, mongoCertificate);

builder.ConfigureServices(services =>
{
  services.AddApplicationInsightsTelemetryWorkerService();
  services.ConfigureFunctionsApplicationInsights();
  services.AddSingleton<IDeviceSyncService, DeviceSyncService>();
  services.AddSingleton(mongoDBService.CreateRepository<ExecutionParameters>("deviceSync"));
 });

IHost host = builder.Build();

host.Run();

函数代码 #

private readonly ILogger _logger = loggerFactory.CreateLogger<DeviceSyncFunction>();
private readonly IDeviceSyncService _deviceSyncService = deviceSyncService;

[Function("DeviceSyncFunction")]
public void Run([TimerTrigger("%TimerExpression%", RunOnStartup = true)] TimerInfo timerInfo)
{
  try
  {
      _logger.LogInformation($"Timer trigger function executed at: {DateTime.UtcNow} UTC");

      _deviceSyncService.GenerateDevices();

      _logger.LogInformation($"Timer trigger function terminated at: {DateTime.UtcNow} UTC");
    }
    catch (OperationCanceledException opex)
    {
      _logger.LogWarning(opex, opex.Message);
    }
    catch (FhirOperationException ex)
    {
      _logger.LogError(ex, ex.Message, ex.StackTrace);
    }
    catch (Exception ex)
    {
      _logger.LogCritical(ex, ex.Message);
    }
 }

.csproj项目文件 #

<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <OutputType>Exe</OutputType>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
</PropertyGroup>

<ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
    <None Include="local.settings.json">
        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
        <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>     
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.21.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http"Version="3.1.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="1.2.1"/>
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Timer" Version="4.3.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.17.2"/>
    <PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.22.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="1.2.0" />
</ItemGroup>

<ItemGroup>
 <ProjectReference Include="..\AE.Resp.Device.Sync.Model\AE.Resp.Device.Sync.Model.csproj" />
  <ProjectReference Include="..\AE.Resp.Device.Sync.Service\AE.Resp.Device.Sync.Service.csproj" />

 <ItemGroup>
    <None Update="host.json">
        <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </None>
 </ItemGroup>

  <ItemGroup>
      <Using Include="System.Threading.ExecutionContext" Alias="ExecutionContext" />
  </ItemGroup>  

</Project>

故障排查思路 #

• 检查函数类访问修饰符：DeviceSyncFunction类必须是public，.NET Isolated模式下宿主只会扫描public类中的函数。
• 修正TimerTrigger配置键：函数中用了%TimerExpression%，但配置文件里的键是TimeTriggerSchedule，两者不匹配，需统一为同一个键名。
• 调整Program.cs的配置加载方式：ConfigureFunctionsWebApplication已自动加载local.settings.json，手动创建ConfigurationBuilder可能导致配置冲突，建议通过依赖注入获取配置（比如在ConfigureServices中通过context.Configuration访问）。
• 修复函数构造注入：当前函数中的_logger和_deviceSyncService是直接赋值的，正确做法是通过构造函数注入实例，而非直接初始化，否则宿主无法正确识别函数。
• 修复.csproj的XML结构：项目文件中存在嵌套的<ItemGroup>标签（第二个ItemGroup内部又嵌套了一个ItemGroup），这是无效的XML，会导致MSBuild解析错误，需调整为正确的层级结构。
• 清理重建项目：删除bin、obj目录，重新build项目，避免旧编译文件干扰。
• 对比正常项目的依赖与配置：将本地可正常运行的Azure Function项目的.csproj依赖版本、Program.cs结构、函数类实现与当前项目逐一对比，找出差异点。
• 检查环境变量覆盖：确认系统级环境变量中是否存在FUNCTIONS_WORKER_RUNTIME，避免其覆盖local.settings.json中的配置。

内容的提问来源于stack exchange，提问作者GIovanni