多线程单例 WCF 服务 [英] Multithreaded Singleton WCF Service

问题描述

在他的WCF 服务编程"一书中，Juval Lowry 表达了对使用单例服务的担忧，因为它会影响性能.

In his book "Programming WCF Services", Juval Lowry expresses concerns about using Singleton Services because of the performance implications.

在我的一个项目中，我使用了一个无状态单例 WCF 服务，声明如下:

In one of my projects I'm using a stateless singleton WCF Service declared like this:

[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single,
   ConcurrencyMode = ConcurrencyMode.Multiple)]
public class FooService : IFoo
{
}

从多个 Silverlight 客户端通过 httpsTransport 访问该服务.我选择了单例，因为我认为没有必要在不需要时给系统增加 GC 开销.我是否遗漏了某些东西，或者这不应该是实现无状态服务的最有效方法，该服务即使不比 PerCall 实例化服务更快，也同样快?

The service is accessed from multiple Silverlight clients over httpsTransport. I've opted for a singleton because I see no need to burden the system the GC overhead when it is not really needed. Am I missing something or shouldn't this be the most efficient way to implement a stateless service that's equally fast if not faster than a PerCall instantiated service?

推荐答案

您没有遗漏任何东西.如果您的服务类没有实例成员变量，这些变量代表的状态显然可能会被多线程访问破坏，那么就没有什么可担心的.

You're not missing anything. If your service class has no instance member variables, which would represent state that could obviously be corrupted by multi-threaded access, there is nothing to fear.

我个人总是使用 Single+Mulitple 模式，因为我的所有状态总是来自缓存或 SQL 数据库或其他一些共享资源，在这些资源中，您无论如何都需要模式来防止并发.我从未在我的服务中发现需要成员变量.静力学?当然可能，但你知道无论如何都要保护他们.

I personally always use Single+Mulitple mode because all of my state is always coming from a cache or SQL database or some other shared resource where you need patterns to guard against concurrency anyway. I've never found a need for member variables in my services. Statics? Sure maybe, but then you know to protect them anyway.

现在这是我个人对 PerCall 与 Single 的看法.PerSession 另一方面，服务可以/很可能会在实例中维护状态，但我个人发现自己并没有写很多这样的东西，而且在极少数情况下，它们是 ConcurrencyMode.Single无论如何.

Now this is all my personal opinion on PerCall vs. Single. PerSession services on the other hand could/most likely would have state maintained in the instance, but I personally don't find myself writing many of those and on the rare occasion I have, they are ConcurrencyMode.Single anyway.

查看这篇 MSDN 文章差异的更多讨论和实际性能比较.模式.

Check out this MSDN article for more discussion and actual performance comparison of the diff. Modes.

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