azure - 使用非静态触发器创建 IFunctionProvider

Question

我有一个 Azure Function 的 IFunctionProvider 实现，它为 /healthcheck 创建路由。我的函数元数据的入口点是一个名为 Somenamespace.TestTrigger.RenderHealthCheck 的方法。我的代码如下所示:

    public class TestTrigger
    {
        public static async Task<IActionResult> RenderHealthCheck(HttpRequest req)
        {
            return new OkObjectResult("OK");
        }        
    }
    
    public class HealthCheckTrigger : IFunctionProvider
    {
        public ImmutableDictionary<string, ImmutableArray<string>> FunctionErrors { get; }
        
        public async Task<ImmutableArray<FunctionMetadata>> GetFunctionMetadataAsync()
        {
            var assembly = Assembly.GetExecutingAssembly();
            
            var functionMetadata = new FunctionMetadata()
            {
                Name = nameof(TestTrigger.RenderHealthCheck),
                FunctionDirectory = null,
                ScriptFile = $"assembly:{assembly.FullName}",
                EntryPoint = $"{typeof(TestTrigger).FullName}.{nameof(TestTrigger.RenderHealthCheck)}",
                Language = "DotNetAssembly"
            };

            var jo = JObject.FromObject(new HttpBindingMetadata()
            {
                Methods = new List<string> { HttpMethods.Get },
                Route = "HealthCheck",
                AuthLevel = AuthorizationLevel.Anonymous,
            });
            
            var binding = BindingMetadata.Create(jo);
            functionMetadata.Bindings.Add(binding);            
            
            var functionMetadataList = new List<FunctionMetadata>
            {
                functionMetadata
            };

            return await Task.FromResult(functionMetadataList.ToImmutableArray()).ConfigureAwait(false);
        }
    }

这工作正常，当我运行该函数并点击 /HealthCheck 端点时，我收到了 OK 消息。但是，我希望使 RenderHealthCheck 方法成为非静态的，这样我就可以在构造函数中使用依赖项注入(inject)并访问应用程序中的各种服务。我将代码更改为:

public class TestTrigger
{
    private readonly HealthCheckService healthCheckService;
    
    public TestTrigger(HealthCheckService healthCheckService)
    {
        this.healthCheckService = healthCheckService;
    }

    public async Task<IActionResult> RenderHealthCheck(HttpRequest req)
    {
        return new OkObjectResult("OK");
    }        
}

现在，当我到达端点时，我收到以下异常:

Executed 'Functions.RenderHealthCheck' (Failed, Id=c02a9ba6-1ed3-4c07-8b38-214d345b6ff1, Duration=488ms)
Microsoft.Azure.WebJobs.Host.FunctionInvocationException: Exception while executing function: Functions.RenderHealthCheck
 ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at lambda_method(Closure , TestTrigger , Object[] )
   at Microsoft.Azure.WebJobs.Host.Executors.TaskMethodInvoker`2.InvokeAsync(TReflected instance, Object[] arguments) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\TaskMethodInvoker.cs:line 21
   at Microsoft.Azure.WebJobs.Script.Description.DotNetFunctionInvoker.MethodInvoker`2.InvokeAsync(Object target, Object[] parameters) in D:\a\1\s\src\WebJobs.Script\Description\DotNet\DotNetFunctionInvoker.cs:line 533
   at Microsoft.Azure.WebJobs.Script.Description.DotNetFunctionInvoker.InvokeCore(Object[] parameters, FunctionInvocationContext context) in D:\a\1\s\src\WebJobs.Script\Description\DotNet\DotNetFunctionInvoker.cs:line 272
   at Microsoft.Azure.WebJobs.Script.Description.FunctionInvokerBase.Invoke(Object[] parameters) in D:\a\1\s\src\WebJobs.Script\Description\FunctionInvokerBase.cs:line 82
   at Microsoft.Azure.WebJobs.Script.Description.FunctionGenerator.Coerce[T](Task`1 src) in D:\a\1\s\src\WebJobs.Script\Description\FunctionGenerator.cs:line 225
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionInvoker`2.InvokeAsync(Object instance, Object[] arguments) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionInvoker.cs:line 52
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.InvokeWithTimeoutAsync(IFunctionInvoker invoker, ParameterHelper parameterHelper, CancellationTokenSource timeoutTokenSource, CancellationTokenSource functionCancellationTokenSource, Boolean thro
wOnTimeout, TimeSpan timerInterval, IFunctionInstance instance) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 555
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithWatchersAsync(IFunctionInstanceEx instance, ParameterHelper parameterHelper, ILogger logger, CancellationTokenSource functionCancellationTokenSource) in C:\projects\azure-webjobs-sdk-r
qm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 503
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(IFunctionInstanceEx instance, FunctionStartedMessage message, FunctionInstanceLogEntry instanceLogEntry, ParameterHelper parameterHelper, ILogger logger, CancellationToken
 cancellationToken) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 281
   --- End of inner exception stack trace --

我在 FunctionMetadata 或 HttpBindingMetadata 中没有看到任何似乎控制入口点是否静态的内容。实例方法根本不支持吗？如果没有的话，这似乎是一个巨大的限制。 IFunctionProvider 上的任何类型的文档基本上都是零，因此不太确定从哪里开始。任何帮助将不胜感激!

Answer 1

如果您确实希望能够将 HealthCheckService 注入(inject)到静态函数中，可以为其创建自定义绑定(bind)并从 FunctionExecutionContext 解析服务。

基于https://microsoft.github.io/AzureTipsAndTricks/blog/tip247.html ，我能够执行以下操作:

[assembly: WebJobsStartup(typeof(HealthBindingStartup))]

[Binding]
[AttributeUsage(AttributeTargets.Parameter)]
public class HealthAttribute : Attribute
{
}

[Extension(nameof(HealthBinding))]
public class HealthBinding : IExtensionConfigProvider
{
    public void Initialize(ExtensionConfigContext context)
    {
        var rule = context.AddBindingRule<HealthAttribute>();
        rule.BindToInput((HealthAttribute attr, ValueBindingContext context) =>
        {
            var service = context.FunctionContext.CreateObjectInstance<HealthCheckService>();

            return Task.FromResult(service);
        });
    }
}

public static class HealthBindingExtension
{
    public static IWebJobsBuilder AddHealthBinding(this IWebJobsBuilder builder)
    {
        if (builder == null)
        {
            throw new ArgumentNullException(nameof(builder));
        }

        builder.AddExtension<HealthBinding>();
        return builder;
    }
}

public class HealthBindingStartup : IWebJobsStartup
{
    public void Configure(IWebJobsBuilder builder)
    {
        builder.AddHealthBinding();
    }
}

有了这个，您可以更新您的函数并添加[Health] HealthCheckService 服务，并让此绑定(bind)注入(inject)您想要的服务。

此绑定(bind)的元数据是:

{ "name": "service", "type": "health", "direction": "in" }

这是通过忽略任何属性的 IFunctionProvider 添加函数时所需要的。