如何在OWIN自托管应用中预加载数据

Question

I have a OWIN/Katana self-hosted service app. One of its functions is to service some data over WebAPI. In this app I have a class called dataManager, which is responsible for retrieving the data, and passing it onto the API controller, which asked for it. The data is ultimately served to a mobile platform, so it is very important to cache as much as possible for performance. Is there a way to pre-load my DataManager at the application startup, and have it pre-execute it's linq queries?

The Application class looks like this:

namespace TaskManager
{
  using System;
  using Microsoft.Owin.Hosting;

  public class TaskManagerApplication
  {
    protected IDisposable WebApplication;

    public void Start()
    {
      WebApplication = WebApp.Start<WebPipeline>("http://*:8080");
    }

    public void Stop()
    {
      WebApplication.Dispose();
    }
  }
}

The Program class looks like this:

namespace TaskManager
{
  using Topshelf;

  internal class Program
  {
    private static int Main()
    {
      var exitCode = HostFactory.Run(host =>
      {
        host.Service<TaskManagerApplication>(service =>
        {
          service.ConstructUsing(() => new TaskManagerApplication());
          service.WhenStarted(a => a.Start());
          service.WhenStopped(a => a.Stop());
        });

        host.SetDescription("Task Manager");
        host.SetDisplayName("Task Manager");
        host.SetServiceName("TaskManager");

        host.RunAsNetworkService();
      });

      return (int) exitCode;
    }
  }
}

And the data retrieval statement contained within DataManager class look like this:

var rawData = from data in new XPQuery<AccountView3.PipelineData>(uow)
                               where data.Stage.ToLower().Contains("won")
                                   && data.RevenueStartDate.Value.Year == DateTime.Today.Year
                                   && data.WeekOfTheYear >= priorWeekCutoff
                               select data;

Answer 1

What I do is create a public static class in the API library. That's where I modify the HttpConfiguration object. That is also where I define OnStartup() and OnShutdown() methods. I then call these methods in the pipeline class's methods (your WebPipeline class).

For example (in the MyWebApi library, where my controllers and stuff live):

public class Service
{
    public static void Register(HttpConfiguration config)
    {
        config.MapHttpAttributeRoutes();
        config.EnsureInitialized();
    }

    public static void OnStartup()
    {
        // add any startup logic here, like caching your data
    }

    public static void OnShutdown()
    {
        // add any cleanup logic here
    }
}

Then in the pipeline class:

public class WebPipeline
{
    public static void Configuration(IAppBuilder app)
    {
        var config = new HttpConfiguration();

        MyWebApi.Service.Register(config);
        MyWebApi.Service.OnStartup();

        app.UseWebApi(config);
    }

    public static void Shutdown()
    {
        MyWebApi.Service.OnShutdown();
    }
}

Now your TaskManagerApplication.Start() will result in the API OnStartup() being called. Then you just have to add a call to WebPipeline.Shutdown() in your TaskManagerApplication.Stop() method.