Executing method by timer inside threadpool
In my multi threaded web app I invoke in the ThreadPool
SomeMethod
which can throw an exception. Suppose I want to make a few at开发者_StackOverflowtempts if it causes an exception at first call. I decide to use System.Timers.Timer inside my action for attempts. Can I use the code below? Is it safely?
static void Caller()
{
ThreadPool.QueueUserWorkItem(action =>
{
try
{
SomeMethod();
Console.WriteLine("Done.");
}
catch
{
var t = new System.Timers.Timer(1000);
t.Start();
var count = 0;
t.Elapsed += new System.Timers.ElapsedEventHandler((o, a) =>
{
var timer = o as System.Timers.Timer;
count++;
var done = false;
Exception exception = null;
try
{
Console.WriteLine(count);
SomeMethod();
done = true;
}
catch (Exception ex)
{
exception = ex;
}
if (done || count == 10)
{
Console.WriteLine(String.Format("Stopped. done: {0}, count: {1}", done, count));
t.Stop();
if (!done) throw exception;
}
});
}
});
Thread.Sleep(100000);
}
static void SomeMethod()
{
var x = 1 / new Random().Next(0, 2);
}
You should Dispose each Timer
after use, that's for sure. But, probably you could do something even simpler:
static void Main()
{
ThreadPool.QueueUserWorkItem(action =>
{
while (TrySomeMethod() == false)
Thread.Sleep(1000);
});
// wait here
Console.Read();
}
static bool TrySomeMethod()
{
try
{
SomeMethod();
return true;
}
catch
{
return false;
}
}
I do not think that using a timer in a thread pool thread is a safe approach. I may be wrong, but the timer will raise its elapsed event when the thread method has already been finished to execute. In this case, the exception will be thrown. Also, I do not see that you are not disposing the timer which leads to resource leaks. If you explain why you need the timer, I will try to find a safe solution...
I don't see the point of using a Timer within a ThreadPool queue, because the ThreadPool would spawn a new thread, and the Timer would spawn a new thread as well.
I would just have a loop within that delegate, because it would not block the main thread either way. Groo showed a good example of that.
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