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在ASP.NET上启动维护过程的最佳实践是什么

2023-04-14 07:54:00

What is the Best Practice to Kick-off Maintenance Process on ASP.NET

对于ASP.NET应用程序，我需要定期(每天，每小时等)运行维护过程。

在不依赖于服务器上预定任务之类的外部流程的情况下，实现此目标的最佳方法是什么(假设我无权访问服务器-共享主机环境)。

这是StackOverflow的执行方式：

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private static CacheItemRemovedCallback OnCacheRemove = null;

protected void Application_Start(object sender, EventArgs e)
{
AddTask("DoStuff", 60);
}

private void AddTask(string name, int seconds)
{
OnCacheRemove = new CacheItemRemovedCallback(CacheItemRemoved);
HttpRuntime.Cache.Insert(name, seconds, null,
DateTime.Now.AddSeconds(seconds), Cache.NoSlidingExpiration,
CacheItemPriority.NotRemovable, OnCacheRemove);
}

public void CacheItemRemoved(string k, object v, CacheItemRemovedReason r)
{
// do stuff here if it matches our taskname, like WebRequest
// re-add our task so it recurs
AddTask(k, Convert.ToInt32(v));
}

详细信息：http://blog.stackoverflow.com/2008/07/easy-background-tasks-in-aspnet/

尽管Cache解决方案适用于简单情况，但如果您的日程安排需要更改，您将很不走运。相反，您可以使用Quartz.NET，它是流行的Java框架Quartz的端口，它非常灵活。

如果您不需要按计划的时间执行此操作，而只需要"偶尔一次"清理，则一种方法是在Global.asax Session_OnEnd()中创建一个函数，该函数将创建一个随机变量。 1到100之间的数字，如果数字是50，则执行维护任务。

偏离路线时，您可以减少" 100"，以使任务更频繁地发生。

在http://www.codeproject.com/aspnet/ASPNETService.asp上也有标题为"使用ASP.NET模拟Windows服务以运行计划的作业"的文章，该文章使用过期缓存来模拟计时器。它声称它可以在任何托管站点上运行。

如果您使用的是最后一种，请从有关此技术的帖子中阅读此评论：

You need to really be careful on the
length of the task running. Every new
Task is a new Worker Thread and
there’s a limited number of those - as
it"borrows" a thread from the managed
thread pool.

Starting in v3.5 of the Framework the
maximum number of threads was
increased 10x from 25 to 250. But
there’s now a logarithmic startup to
them, so as it doles out more threads
it gets stingier with them. If you run
out of available threads in the
managed thread pool - your response
times are going to go through the
roof.

What you’re really writing here is a
messaging/queuing system.

If you’re doing things like updating
the cache, then by all means - kick
off a new task. If you’re doing
something like downloading a secondary
HTTP resource or some kind of
intensive database work - write a
Windows Service and use a Queue that
allows you more control over how much
you"bite" off each time.