asp.net - 使用 OWIN 的 Web API 会针对 HttpMessageInvoker 引发 ObjectDisposeException

Question

我在 ASP.NET WebApi2 设置中使用 OWIN 时遇到一些困难。重启后的第一个请求会导致异常:

    [ObjectDisposedException: Cannot access a disposed object.    Object name: 'System.Net.Http.HttpMessageInvoker'.]       System.Net.Http.HttpMessageInvoker.CheckDisposed() +327456       System.Net.Http.HttpMessageInvoker.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +24       System.Web.Http.Owin.<InvokeCore>d__0.MoveNext() +501       System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99       System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58       Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.<RunApp>d__5.MoveNext() +187       System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99       System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58       Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.<DoFinalWork>d__2.MoveNext() +185       Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.StageAsyncResult.End(IAsyncResult ar) +69       Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.EndFinalWork(IAsyncResult ar) +64       System.Web.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +483       System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +157    

I believe the problem is caused by a long running task when its hitting the EF DbContext for the first time. All in all the first request is around 4-6000ms. After this first request there are no more exceptions.

I have reproduced the issue in a simplified form with a webapi project and the following OWIN startup (and no global.asax):

public class Startup
{
    public void Configuration(IAppBuilder app) {
        var config = new HttpConfiguration();
        config.MapHttpAttributeRoutes();

        // ---- simulate long running initialization code -------
        Thread.Sleep(3000);
        // ------------------------------------------------------

        app.UseWebApi(config);
    }
}

我添加一个 Controller :

[Route("api/test/number")]
public class TestController : ApiController
{
    public object Get() {
        return 42;
    }
}

当我请求此请求时，第一个请求会导致异常。

Answer 1

这是一个老问题，但只是花了几个小时试图击败 ObjectDisposeException，并且刚刚找到了一个解决方案，此 AspNetWebStack issue on codeplex帮助我:

当您的 owin Web api 应在自托管环境中运行时，您可以在 owin 启动类中绑定(bind) Web api 配置

public void Configuration(IAppBuilder app)
{
    ConfigureOAuth(app);

    HttpConfiguration config = new HttpConfiguration();
    WebApiConfig.Register(config);
    app.UseWebApi(config);
}

如果您打算使用 IIS 作为 owin Web api 的主机，则在全局 asax 类中绑定(bind) Web api 配置

protected void Application_Start(object sender, EventArgs e)
{
    GlobalConfiguration.Configure(WebApiConfig.Register);
}

这消除了 ObjectDisposeException，我的 Web api 运行得非常顺利