Alternatives to Thread.Sleep()

Question

Every N minutes we want to run through a list of tasks. So we've created a task executor with a

do { DoWork(); }while(!stopRequested) 

Now we want to have a pause between work cycles. Everyone seems to think Thread.Sleep() is the devil. I've seen mention of using Monitor/Event stuff but we don't have someone else telling us to do work. We just want to do stuff every N minutes like clockwork.

So is there an alternative or have I found a valid use of Thread.Sleep?

Someone in another post mentioned WaitHandle.WaitOne() as an alternative but you can't call that from a non-static method apparently? Or at least I can't because I get a compile time error of..

An object reference is required for the non-static field, method, or property 'System.Threading.WaitHandle.WaitOne(System.TimeSpan)'

Answer 1

By my understanding, Thread.Sleep() is bad because it forces the thread's resources out of the cache, so they have to be loaded again afterwards. Not a big deal, but it could aggravate performance issues in high-load situations. And then there's the fact that the timing isn't precise, and that it effectively can't wait for durations under about 10ms...

I use this snippet:

new System.Threading.ManualResetEvent(false).WaitOne(1000); 

Easy as pie and it all fits on one line. Creates a new event handler that will never be set, and then waits the full timeout period, which you specify as the argument to WaitOne().

Although, for this specific scenario, a Timer would probably be a more appropriate approach:

var workTimer = new System.Threading.Timer(     (x) => DoWork(),     null,     1000, // initial wait period     300000); // subsequent wait period 

Then, instead of setting a cancel variable, you would stop the timer with workTimer.Stop().

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Edit:

Since people are still finding this useful, I should add that .NET 4.5 introduces the Task.Delay method, which is even more concise and also supports async:

Task.Delay(2000).Wait(); // Wait 2 seconds with blocking await Task.Delay(2000); // Wait 2 seconds without blocking 

Answer 2

You have to call WaitOne on a WaitHandle, certainly. It's an instance method. Otherwise how would it know what to wait for?

It's definitely better to have something you can react to instead of sleep, so that you can notice cancellation without waiting minutes for no reason. Another alternative to WaitHandle is to use Monitor.Wait/Pulse.

However, if you're using .NET 4 I'd look into what the Task Parallel Library has to offer... it's at a slightly higher level than the other options, and is generally a well thought out library.

For regular work tasks you might want to look at using a Timer (either System.Threading.Timer or System.Timers.Timer) or possibly even Quartz.NET.