问题描述
在我的 asp.net core 5.0 应用程序中,我调用了一个可能需要一些时间来处理的异步方法。
await someObject.LongRunningProcess(cancelationToken);
但是,我希望该方法在 5 秒后超时。我知道,我可以使用“CancellationTokenSource”,而不是通过 asp.net 核心操作传递的“cancelationToken”:
var s_cts = new CancellationTokenSource();
s_cts.CancelAfter(TimeSpan.FromSeconds(5);
await someObject.LongRunningProcess(s_cts );
是否可以将“CancellationTokenSource”用作所有 asp.net 核心请求的默认“取消令牌”策略?我的意思是覆盖作为动作参数传递的那个?
或者是否可以更改 asp.net core 5.0 中所有请求的默认超时时间?
[更新]
解决方法
解决这个问题的一种方法是将该逻辑包装在一个类中。编写一个运行具有可配置超时的任务的类。
然后在 DI 中注册它,然后在任何你想重用配置的地方使用它。
public class TimeoutRunner
{
private TimeoutRunnerOptions _options;
public TimeoutRunner(IOptions<TimeoutRunnerOptions> options)
{
_options = options.Value;
}
public async Task<T> RunAsync<T>(Func<CancellationToken,Task<T>> runnable,CancellationToken cancellationToken = default)
{
// cancel the task as soon as one of the tokens is set
var timeoutCts = new CancellationTokenSource();
var token = timeoutCts.Token;
if (cancellationToken != default)
{
timeoutCts.CancelAfter(_options.Timeout);
var combinedCts = CancellationTokenSource.CreateLinkedTokenSource(timeoutCts.Token,cancellationToken);
token = combinedCts.Token;
}
return await runnable(token);
}
}
internal static class ServiceCollectionExtensions
{
public static IServiceCollection AddTimeoutRunner(this IServiceCollection services,Action<TimeoutRunnerOptions> configure = null)
{
if (configure != null)
{
services.Configure<TimeoutRunnerOptions>(configure);
}
return services.AddTransient<TimeoutRunner>();
}
}
public class TimeoutRunnerOptions
{
public int TimeoutSeconds { get; set; } = 10;
public TimeSpan Timeout => TimeSpan.FromSeconds(TimeoutSeconds);
}
然后你会在 Startup 类中注册它,
public void ConfigureServices(IServiceCollection services)
{
services.AddTimeoutRunner(options =>
{
options.TimeoutSeconds = 10;
});
}
然后在需要全局选项的任何地方使用它:
public class MyController : ControllerBase
{
private TimeoutRunner _timeoutRunner;
public MyController(TimeoutRunner timeoutRunner)
{
_timeoutRunner = timeoutRunner;
}
public async Task<IActionResult> DoSomething(CancellationToken cancellationToken)
{
await _timeoutRunner.RunAsync(
async (CancellationToken token) => {
await Task.Delay(TimeSpan.FromSeconds(20),token);
},cancellationToken
);
return Ok();
}
}
在每个动作分派前运行一个任务
方法 1:操作过滤器
我们可以使用动作过滤器在每个请求之前/之后运行任务。
public class ApiCallWithTimeeotActionFilter : IAsyncActionFilter
{
private TimeoutRunner _runner;
public ApiCallWithTimeeotActionFilter(TimeoutRunner runner)
{
_runner = runner;
}
public async Task OnActionExecutionAsync(ActionExecutingContext context,ActionExecutionDelegate next)
{
var result = await _runner.RunAsync(
async (CancellationToken token) =>
{
await Task.Delay(TimeSpan.FromSeconds(20),token);
return 42;
},default
);
await next();
}
}
然后使用它用 [TypeFilter(typeof(MyAction))]
注释一个类:
[TypeFilter(typeof(ApiCallWithTimeeotActionFilter))]
public class MyController : ControllerBase { /* ... */ }
方法 2:中间件
另一种选择是使用中间件
class ApiCallTimeoutMiddleware
{
private TimeoutRunner _runner;
public ApiCallTimeoutMiddleware(TimeoutRunner runner)
{
_runner = runner;
}
public async Task InvokeAsync(HttpContext context,RequestDelegate next)
{
// run a task before every request
var result = await _runner.RunAsync(
async (CancellationToken token) =>
{
await Task.Delay(TimeSpan.FromSeconds(20),default
);
await next(context);
}
}
然后在 Startup.Configure
方法中附加中间件:
public void Configure(IApplicationBuilder app)
{
app.UseMiddleware<ApiCallTimeoutMiddleware>();
app.UseRouting();
app.UseEndpoints(e => e.MapControllers());
}
,
自定义传递给操作的 CancellationToken
您需要替换将 CancellationTokenModelBinderProvider
令牌绑定到操作的 HttpContext.RequestAborted
参数的默认 CancellationToken
。
这涉及创建自定义 IModelBinderProvider
。然后我们可以用我们自己的替换默认绑定结果。
public class TimeoutCancellationTokenModelBinderProvider : IModelBinderProvider
{
public IModelBinder? GetBinder(ModelBinderProviderContext context)
{
if (context?.Metadata.ModelType != typeof(CancellationToken))
{
return null;
}
var config = context.Services.GetRequiredService<IOptions<TimeoutOptions>>().Value;
return new TimeoutCancellationTokenModelBinder(config);
}
private class TimeoutCancellationTokenModelBinder : CancellationTokenModelBinder,IModelBinder
{
private readonly TimeoutOptions _options;
public TimeoutCancellationTokenModelBinder(TimeoutOptions options)
{
_options = options;
}
public new async Task BindModelAsync(ModelBindingContext bindingContext)
{
await base.BindModelAsync(bindingContext);
if (bindingContext.Result.Model is CancellationToken cancellationToken)
{
// combine the default token with a timeout
var timeoutCts = new CancellationTokenSource();
timeoutCts.CancelAfter(_options.Timeout);
var combinedCts =
CancellationTokenSource.CreateLinkedTokenSource(timeoutCts.Token,cancellationToken);
// We need to force boxing now,so we can insert the same reference to the boxed CancellationToken
// in both the ValidationState and ModelBindingResult.
//
// DO NOT simplify this code by removing the cast.
var model = (object)combinedCts.Token;
bindingContext.ValidationState.Clear();
bindingContext.ValidationState.Add(model,new ValidationStateEntry() { SuppressValidation = true });
bindingContext.Result = ModelBindingResult.Success(model);
}
}
}
}
class TimeoutOptions
{
public int TimeoutSeconds { get; set; } = 30; // seconds
public TimeSpan Timeout => TimeSpan.FromSeconds(TimeoutSeconds);
}
然后将此提供程序添加到 Mvc 的默认绑定程序提供程序列表中。它需要在所有其他人之前运行,所以我们在开头插入它。
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
services.Configure<MvcOptions>(options =>
{
options.ModelBinderProviders.RemoveType<CancellationTokenModelBinderProvider>();
options.ModelBinderProviders.Insert(0,new TimeoutCancellationTokenModelBinderProvider());
});
// remember to set the default timeout
services.Configure<TimeoutOptions>(configuration => { configuration.TimeoutSeconds = 2; });
}
现在 ASP.NET Core 将在看到 CancellationToken
类型的参数时运行您的绑定器,该参数将 HttpContext.RequestAborted
令牌与我们的超时令牌结合在一起。每当其组件之一被取消(由于超时或请求中止,以先取消者为准)时,就会触发组合令牌
[HttpGet("")]
public async Task<IActionResult> Index(CancellationToken cancellationToken)
{
await Task.Delay(TimeSpan.FromSeconds(5),cancellationToken); // throws TaskCanceledException after 2 seconds
return Ok("hey");
}
参考文献:
- https://github.com/dotnet/aspnetcore/blob/348b810d286fd2258aa763d6eda667a83ff972dc/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinder.cs
- https://abdus.dev/posts/aspnetcore-model-binding-json-query-params/
- https://docs.microsoft.com/en-us/aspnet/core/mvc/advanced/custom-model-binding?view=aspnetcore-5.0#custom-model-binder-sample