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Dispose.Scope

Dispose.Scope是一个可以让你方便的使用作用域管理实现了IDisposable接口的对象实例的类库。将需要释放的IDisposable注册到作用域中,然后在作用域结束时自动释放所有注册的对象。

使用方式

Dispose.Scope使用非常简单,只需要几步就能完成上文中提到的功能。首先安装Nuget包:

NuGet

Install-Package Dispose.Scope
dotnet add package Dispose.Scope
paket add Dispose.Scope

你可以直接使用Dispose.Scope的API,本文的所有样例你都可以在samples文件夹中找到,比如我们有一个类叫NeedDispose代码如下:

public class NeedDispose : IDisposable
{
    public NeedDispose(string name)
    {
        Name = name;
    }
    public string Name { get; set; }
    
    public void Dispose()
    {
        Console.WriteLine("Dispose");
    }
}

然后我们就可以像下面这样使用DisposeScope

using Dispose.Scope;

using (var scope = DisposeScope.BeginScope())
{
    var needDispose = new NeedDisposeClass("A1");
    // register to current scope
    needDispose.RegisterDisposeScope();
}
// output: A1 Is Dispose

同样,在异步上下文中也可以使用DisposeScope

using (var scope = DisposeScope.BeginScope())
{
    await Task.Run(() =>
    {
        var needDispose = new NeedDispose("A2");
        // register to current scope
        needDispose.RegisterDisposeScope();
    });
}
// output: A2 Is Dispose

当然我们可以在一个DisposeScope的作用域当中,嵌套多个DisposeScope,如果上下文中存在DisposeScope那么他们会直接使用上下文中的,如果没有那么他们会创建一个新的。

using (_ = DisposeScope.BeginScope())
{
    var d0 = new NeedDispose("D0").RegisterDisposeScope();
    
    using (_ = DisposeScope.BeginScope())
    {
        var d1 = new NeedDispose("D1").RegisterDisposeScope();
    }
    using (_ = DisposeScope.BeginScope())
    {
        var d2 = new NeedDispose("D2").RegisterDisposeScope();
    }
}
// output:
// D0 is Dispose
// D1 is Dispose
// D2 is Dispose

如果你想让嵌套的作用域优先释放,那么作用域调用BeginScope方法时需要指定DisposeScopeOption.RequiresNew(关于DisposeScopeOption选项可以查看下面的的内容),它不管上下文中有没有作用域,都会创建一个新的作用域:

using (_ = DisposeScope.BeginScope())
{
    var d0 = new NeedDispose("D0").RegisterDisposeScope();
   
    using (_ = DisposeScope.BeginScope(DisposeScopeOption.RequiresNew))
    {
        var d1 = new NeedDispose("D1").RegisterDisposeScope();
    }
    using (_ = DisposeScope.BeginScope(DisposeScopeOption.RequiresNew))
    {
        var d2 = new NeedDispose("D2").RegisterDisposeScope();
    }
}
// output:
// D1 Is Dispose
// D2 Is Dispose
// D0 Is Dispose

如果你不想在嵌套作用域中使用DisposeScope,那么可以指定DisposeScopeOption.Suppress,它会忽略上下文的DisposeScope,但是如果你在没有DisposeScope上下文中使用RegisterDisposeScope,默认会抛出异常。

using (_ = DisposeScope.BeginScope())
{
    var d0 = new NeedDispose("D0").RegisterDisposeScope();
    
    using (_ = DisposeScope.BeginScope(DisposeScopeOption.RequiresNew))
    {
        var d1 = new NeedDispose("D1").RegisterDisposeScope();
    }
    using (_ = DisposeScope.BeginScope(DisposeScopeOption.Suppress))
    {
        // was throw exception, because this context is not DisposeScope
        var d2 = new NeedDispose("D2").RegisterDisposeScope();
    }
}
// output:
// System.InvalidOperationException: Can not use Register on not DisposeScope context
//    at Dispose.Scope.DisposeScope.Register(IDisposable disposable) in E:\MyCode\PooledScope\src\Dispose.Scope\DisposeScope.cs:line 100
//    at Program.<<Main>$>g__Method3|0_4() in E:\MyCode\PooledScope\Samples\Sample\Program.cs:line 87
//    at Program.<Main>$(String[] args) in E:\MyCode\PooledScope\Samples\Sample\Program.cs:line 9

如果不想让它抛出异常,那么只需要在开始全局设置DisposeScope.ThrowExceptionWhenNotHaveDisposeScope = false,在没有DisposeScope的上下文中,也不会抛出异常.

// set false, no exceptions will be thrown
DisposeScope.ThrowExceptionWhenNotHaveDisposeScope = false;
using (_ = DisposeScope.BeginScope())
{
    var d0 = new NeedDispose("D0").RegisterDisposeScope();
    
    using (_ = DisposeScope.BeginScope(DisposeScopeOption.RequiresNew))
    {
        var d1 = new NeedDispose("D1").RegisterDisposeScope();
    }
    using (_ = DisposeScope.BeginScope(DisposeScopeOption.Suppress))
    {
        // no exceptions will be thrown
        var d2 = new NeedDispose("D2").RegisterDisposeScope();
    }
}
// output:
// D1 Is Dispose
// D0 Is Dispose

DisposeScopeOption

枚举 描述
DisposeScopeOption.Required 作用域内需要 DisposeScope。如果已经存在,它使用环境 DisposeScope。否则,它会在进入作用域之前创建一个新的 DisposeScope。这是默认值。
DisposeScopeOption.RequiresNew 无论环境中是否有 DisposeScope,始终创建一个新的 DisposeScope
DisposeScopeOption.Suppress 创建作用域时会抑制环境 DisposeScope 上下文。作用域内的所有操作都是在没有环境 DisposeScope 上下文的情况下完成的。

Collections.Pooled扩展

本项目一开始的初衷就是为了更方面的使用Collections.Pooled,它基于官方的System.Collections.Generic,实现了基于System.Buffers.ArrayPool的集合对象分配。 基于池的集合对象生成有着非常好的性能和非常低的内存占用。但是您在使用中需要手动为它进行Dispose,这在单一的方法中还好,有时您会跨多个方法,写起来会比较麻烦,而且有时会忘记去释放它,失去了使用Pool的意义,如下所示:

using Collections.Pooled;

Console.WriteLine(GetTotalAmount());

decimal GetTotalAmount()
{
    // forget to dispose `MethodB` result
    var result = GetRecordList().Sum(x => x.Amount);
    return result;
}

PooledList<Record> GetRecordList()
{
    // register to dispose scope
    var list = DbContext.Get().ToPooledList();
    return list;
}

现在您可以添加Dispose.Scope的类库,这样可以在外围设置一个Scope,当方法结束时,作用域内注册的对象都会Dispose

using Dispose.Scope;
using Collections.Pooled;

// dispose the scope all registered objects
using(_ = DisposeScope.BeginScope)
{
    Console.WriteLine(GetTotalAmount());
}

decimal GetTotalAmount()
{
    // forget to dispose `MethodB` result, but don't worries, it will be disposed automatically
    var result = GetRecordList().Sum(x => x.Amount);
    return result;
}

PooledList<Record> GetRecordList()
{
    // register to dispose scope, it will be disposed automatically
    var list = DbContext.Get().ToPooledList().RegisterDisposeScope();
    // or
    var list = DbContext.Get().ToPooledListScope();
    return list;
}

性能

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.22000
Intel Core i7-8750H CPU 2.20GHz (Coffee Lake), 1 CPU, 12 logical and 6 physical cores
.NET SDK=6.0.203
  [Host]     : .NET 6.0.5 (6.0.522.21309), X64 RyuJIT
  DefaultJob : .NET 6.0.5 (6.0.522.21309), X64 RyuJIT
Method Mean Error StdDev Ratio RatioSD Gen 0 Gen 1 Gen 2 Allocated
GetSomeClassUsePooledUsing 169.4 ms 1.60 ms 1.50 ms 0.70 0.01 53333.3333 24333.3333 - 305 MB
GetSomeClassUsePooledScope 169.6 ms 1.47 ms 1.30 ms 0.70 0.01 53000.0000 24333.3333 - 306 MB
GetSomeClass 240.9 ms 1.92 ms 1.60 ms 1.00 0.00 112333.3333 58000.0000 41333.3333 632 MB
GetSomeClassUsePooled 402.2 ms 7.78 ms 8.96 ms 1.68 0.03 83000.0000 83000.0000 83000.0000 556 MB

表格中GetSomeClassUsePooledScope就是使用Dispose.Scope的性能,可以看到它基本和手动using一样,稍微有一点额外的开销就是需要创建DisposeScope对象。

Asp.Net Core扩展

安装Nuget包Dispose.Scope.AspNetCore. NuGet

Install-Package Dispose.Scope.AspNetCore
dotnet add package Dispose.Scope.AspNetCore
paket add Dispose.Scope.AspNetCore

在Asp.Net Core中,返回给Client端是需要Json序列化的集合类型,这种场景下不太好使用Collections.Pooled,因为你需要在请求处理结束时释放它,但是你不能方便的修改框架中的代码,如下所示:

using Collections.Pooled;

[ApiController]
[Route("api/[controller]")]
public class RecordController : Controller
{
    // you can't dispose PooledList<Record>
    PooledList<Record> GetRecordList(string id)
    {
        return RecordDal.Get(id);
    }
}
......
public class RecordDal
{
    public PooledList<Record> Get(string id)
    {
        var result = DbContext().Get(r => r.id == id).ToPooledList();
        return result;
    }
}

现在你可以引用Dispose.Scope.AspNetCore包,然后将它注册为第一个中间件(其实只要在你使用Pooled类型之前即可),然后使用ToPooledListScope或者RegisterDisposeScope方法;这样在框架的求处理结束时,它会自动释放所有注册的对象。

using Dispose.Scope.AspNetCore;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();

var app = builder.Build();
// register UseDisposeScopeMiddleware
// it will be create a scope when http request begin, and dispose it when http request end
app.UseDisposeScope();
app.MapGet("/", () => "Hello World!");
app.MapControllers();
app.Run();

......

[ApiController]
[Route("api/[controller]")]
public class RecordController : Controller
{
    PooledList<Record> GetRecordList(string id)
    {
        return RecordDal.Get(id);
    }
}

......
public class RecordDal
{
    public PooledList<Record> Get(string id)
    {
        // use `ToPooledListScope` to register to dispose scope
        // will be dispose automatically when the scope is disposed
        var result = DbContext().Get(r => r.id == id).ToPooledListScope();
        return result;
    }
}

性能

在ASP.NET Core使用了DisposeScopePooledList,也使用普通的List作为对照组。使用https://github.com/InCerryGit/Dispose.Scope/tree/master/benchmarks代码进行压测,结果如下:

机器配置 Server:1 Core
Client:5 Core 由于是使用CPU亲和性进行绑核,存在Client抢占Server的Cpu资源的情况,结论仅供参考。

项目 总耗时 最小耗时 平均耗时 最大耗时 QPS P95延时 P99延时 内存占用
DisposeScope+PooledList 1997 1 9.4 80 5007 19 31 59MB
List 2019 1 9.5 77 4900 19 31 110MB

通过几次平均取值,使用Dispose.Scope结合PooledList的场景,内存占用率要低53%,QPS高了2%左右,其它指标基本没有任何性的退步。

注意

在使用Dispose.Scope需要注意一个场景,那就是在作用域内有跨线程操作时,比如下面的例子:

using Dispose.Scope;

using(var scope = DisposeScope.BeginScope())
{
    // do something
    _ = Task.Run(() =>
    {
        // do something
        var list = new PooledList<Record>().RegisterDisposeScope();
    });
}

上面的代码存在严重的问题,当外层的作用域结束时,可能内部其它线程的任务还未结束,就会导致对象错误的被释放。如果您遇到这样的场景,您应该抑制上下文中的DisposeScope,然后在其它线程中重新创建作用域。

using Dispose.Scope;

using(var scope = DisposeScope.BeginScope())
{
    // suppress context scope
    using(var scope2 = DisposeScope.BeginScope(DisposeScopeOption.Suppress))
    {
        _ = Task.Run(() =>
        {
            // on other thread create new scope
            using(var scope = DisposeScope.BeginScope())
            {
                // do something
                var list = new PooledList<Record>().RegisterDisposeScope();
            }
        });
    }

}