Windows 服务计划执行 [英] Windows service scheduled execution

问题描述

如果我有一个需要每 30 秒执行一次任务的 Windows 服务，这更好用；Timer() 类或执行任务然后休眠数秒的循环?

If I have a Windows Service that needs to execute a task every 30 seconds which is better to use; the Timer() class or a loop that executes the task then sleeps for a number of seconds?

class MessageReceiver 
{
    public MessageReceiver()
    {
    }

    public void CommencePolling()
    {
        while (true)
        {
            try 
            {
                this.ExecuteTask();     
                System.Threading.Thread.Sleep(30000);
            }
            catch (Exception)
            {
                // log the exception
            }
        }
    }

    public void ExecutedTask()
    {
        // do stuff
    }
}

class MessageReceiver 
{
    public MessageReceiver()
    {
    }

    public void CommencePolling()
    {
        var timer = new Timer()
            {
                AutoReset = true,
                Interval = 30000,
                Enabled = true
            };

        timer.Elapsed += Timer_Tick;    
    }

    public void Timer_Tick(object sender, ElapsedEventArgs args)
    {
        try 
        {
            // do stuff
        }
        catch (Exception)
        {
            // log the exception
        }
    }
}

windows 服务将创建 MessageReciever 类的实例并在新线程上执行 CommencePolling 方法.

The windows service will create an instance of the MessageReciever class and execute the CommencePolling method on a new thread.

推荐答案

我认为这真的取决于您的要求.

I think it really depends on your requirement.

案例 1.假设您想从上午 12:00(即 12:00、12:05，...)开始每五分钟运行一次 this.ExecuteTask() 并假设 this 的执行时间.ExecuteTask() 变化(例如，从 30 秒到 2 分钟)，也许使用计时器而不是 Thread.Sleep() 似乎是一种更简单的方法(至少对我而言).

case 1. Suppose you want to run this.ExecuteTask() every five minutes starting from 12:00AM (i.e., 12:00, 12:05, ...) and suppose the execution time of this.ExecuteTask() varies (for example, from 30 sec to 2 min), maybe using timer instead of Thread.Sleep() seems to be an easier way of doing it (at least for me).

但是，您也可以使用 Thread.Sleep() 实现此行为，方法是在线程唤醒和 this.ExecuteTask() 完成时获取时间戳，同时计算偏移量).

However, you can achieve this behavior with Thread.Sleep() as well by calculating the offset while taking timestamps on a thread wake-up and on a completion of this.ExecuteTask().

案例 2.假设您想在 this.ExecuteTask() 完成后的接下来的 5 分钟内执行任务，使用 Thread.Sleep() 似乎更容易.同样，您也可以使用计时器来实现此行为，方法是每次重置计时器，同时在每次 this.ExecuteTask() 完成时计算偏移量.

case 2. Suppose you want to perform the task in the next 5 min just after completion of this.ExecuteTask(), using Thread.Sleep() seems to be easier. Again, you can achieve this behavior with a timer as well by reseting the timer every time while calculating offsets on every time this.ExecuteTask() completes.

Note1，对于情况 1，您应该在以下场景中非常小心:如果 this.ExecuteTask() 有时需要超过句点(即它在上面的例子中，从 12:05 开始，到 12:13 结束).

Note1, for the case 1, you should be very careful in the following scenario: what if this.ExecuteTask() sometimes takes more than the period (i.e. it starts at 12:05 and completes 12:13 in the example above).

1. 这对您的申请意味着什么?将如何处理?

1. What does this mean to your application and how will it be handled?

一个.完全失败 - 中止服务或在 12:10 中止当前 (12:05) 执行并启动 12:10 执行.
湾没什么大不了的(跳过 12:10 并在 12:15 运行 this.ExecuteTask()).

a. Total failure - abort the service or abort the current(12:05) execution at 12:10 and launch 12:10 execution.
b. Not a big deal (skip 12:10 one and run this.ExecuteTask() at 12:15).

c.没什么大不了的，但需要在 12:05 任务完成后立即启动 12:10 执行(如果持续时间超过 5 分钟怎么办??).

c. Not a big deal, but need to launch 12:10 execution immediately after 12:05 task finishes (what if it keeps taking more than 5 min??).

d.即使 12:05 执行当前正在运行，也需要启动 12:10 执行.

d. Need to launch 12:10 execution even though 12:05 execution is currently running.

e.还有什么吗?

对于您在上面选择的策略，您选择的实现(计时器或 Thread.Sleep())是否容易支持您的策略?

For the policy you select above, does your choice of implementation (either timer or Thread.Sleep()) easy to support your policy?

注意 2.您可以在 .NET 中使用多个计时器.请参阅以下文档(尽管它有点老，但它似乎是一个好的开始):比较.NET Framework 类库中的定时器类

Note2. There are several timers you can use in .NET. Please see the following document (even though it's bit aged, but it seems to be a good start): Comparing the Timer Classes in the .NET Framework Class Library

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