1

我正在使用 EventFlow 来跟踪 ETW 事件。为此，我创建了一个充当侦听器的 ASP Net Core 服务。我已经在我的配置文件中配置了我自己的自定义输出。这些是我的输出和输出工厂类：

class CustomOutput : IOutput
{
    public Task SendEventsAsync(IReadOnlyCollection<EventData> events, long transmissionSequenceNumber, CancellationToken cancellationToken)
    {
        foreach(var e in events)
        {
            //...;
        }
        return Task.CompletedTask;
    }
}

class CustomOutputFactory : IPipelineItemFactory<CustomOutput>
{
    public CustomOutput CreateItem(IConfiguration configuration, IHealthReporter healthReporter)
    {
        return new CustomOutput();
    }
}

此 CustomOutput 仅在启动时（创建 EventFlow 管道时）实例化一次，并用于所有事件。主要方法是这样的：

private static void Main()
{
    try
    {
        using (var diagnosticsPipeline = ServiceFabricDiagnosticPipelineFactory.CreatePipeline("MyApplication-MyService-DiagnosticsPipeline"))
        {

            ServiceRuntime.RegisterServiceAsync("Stateless1Type",
            context => new Stateless1(context)).GetAwaiter().GetResult();

            ServiceEventSource.Current.ServiceTypeRegistered(Process.GetCurrentProcess().Id, typeof(Stateless1).Name);

            Thread.Sleep(Timeout.Infinite);
        }
    }
    catch (Exception e)
    {
        ServiceEventSource.Current.ServiceHostInitializationFailed(e.ToString());
        throw;
    }
}

配置文件 eventFlowConfig.json 中引用了输出和工厂输出类型：

"extensions": [
{
  "category": "outputFactory",
  "type": "CustomOutput",
  "qualifiedTypeName": "MyProyect.Service.MyApp.SqlOutputFactory, MyProyect.Service.MyApp"
}
]

参考：使用 EventFlow 进行事件聚合和收集

因此，实例是在我的 Program 类的 main 方法中创建的，即在调用我的 Startup 配置方法之前。

如果容器在实例化时仍然不存在，我如何从我的输出类访问我的依赖容器服务？

目前，我创建了一个 IServiceCollection 类型的静态属性，并从我的 Startup 配置方法（使用 setter 注入）中设置了它。我不喜欢这个解决方案，因为我不应该对服务使用静态访问，但我不知道其他解决方案。这是一个有效的做法吗？

class CustomOutput : IOutput
{
    public static IServiceCollection Services { get; set; }

    public Task SendEventsAsync(IReadOnlyCollection<EventData> events, long transmissionSequenceNumber, CancellationToken cancellationToken)
    {
        var sp = Services.BuildServiceProvider();
        var loggerFactory = sp.GetService<ILoggerFactory>();
        logger = loggerfactory.CreateLogger<CustomOutput>();
        var repository = serviceProvider.GetService<IMyRepository>();
        foreach (var e in events)
        {
            logger.LogDebug("event...");
            repository.SaveEvent(e);
            //...;
        }
        return Task.CompletedTask;
    }
}

public class Startup
{
    // Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {

        //..
        CustomOutput.Services = services;
        //..
    }
}
4

1 回答 1

1

虽然使用显式依赖原则而不是当前正在实施的服务定位器模式将是更好的选择。目标框架可扩展性的限制使这变得困难。

只留下静态访问器作为可能解决方案的扩展点。

由于CustomOutput只会创建一次，因此在此设计中应该遵循单例模式

public class CustomOutput : IOutput {
    private static Lazy<CustomOutput> instance = 
        new Lazy<CustomOutput>(() => return new CustomOutput());
    private Lazy<ILogger> logger;
    private Lazy<IMyRepository> repository;

    private CustomOutput() { }

    public static CustomOutput Instance {
        get {
            return instance.Value;
        }
    }

    public void Configure(Lazy<ILogger> logger, Lazy<IMyRepository> repository) {
        this.logger = logger;
        this.repository = repository
    }

    public Task SendEventsAsync(IReadOnlyCollection<EventData> events, long transmissionSequenceNumber, CancellationToken cancellationToken) {
        //TODO: Add null check and fail if not already configured.

        foreach (var e in events) {
            logger.Value.LogDebug("event...");
            repository.Value.SaveEvent(e);
            //...;
        }
        return Task.CompletedTask;
    }
}

public class CustomOutputFactory : IPipelineItemFactory<CustomOutput> {
    public CustomOutput CreateItem(IConfiguration configuration, IHealthReporter healthReporter) {
        return CustomOutput.Instance;
    }
}

在上述方法中，依赖项的创建和注入可以推迟到Startup. 以下扩展有助于实现这一点。

public static class CustomOutputServiceCollectionExtensions {

    public IServiceCollection ConfigureCustomOutput(this IServiceCollection services) {
        services.AddTransient<IMyRepository, MyRepository>();

        var logger = new Lazy<ILogger>(() => {
            var sp = services.BuildServiceProvider();
            return sp.GetService<ILogger<CustomOutput>>();
        });

        var repository = new Lazy<IMyRepository>(() => {
            var sp = services.BuildServiceProvider();
            return sp.GetService<IMyRepository>();
        });

        CustomOutput.Instance.Configure(logger, repository);

        return services;
    }

}

然后将从中调用它Startup；

public class Startup {

    //...

    // Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services) {

        //...

        services.ConfigureCustomOutput();

        //...
    }
}
于 2018-04-16T19:23:16.663 回答