Question

I use the following code in a asp.net website.

On application init i call InitializeTimer() once.

The goal of the code was to run DoWork() once every hour (1 time per hour) .

I also wanted the code to execute on different time every loop so i added the random part.

The result i got was werid , i can not find a explaination why is happens.

The code executed the function after 2hrs , then again after 2hrs , then after 3hrs , then after 2hrs , and 2hrs again.****

Can anybody explain the reason?

using System.Timers;
....
private static random = new Random();
....
public static void InitializeTimer()
{
    tTimer = new Timer();
    tTimer.AutoReset = true;
    tTimer.Interval = TimeSpan.FromHours(1.0).TotalMilliseconds;
    tTimer.Elapsed += new ElapsedEventHandler(ClassName1.tMailer_Elapsed);
    tTimer.Start();
}

private static void tTimer_Elapsed(object sender, ElapsedEventArgs e)
{
    tTimer.Interval += random.Next(-5, 5);

    DoWork();
}

Update:

1. Please don’t post “use windows service” , or “scheduled task”.
   My question is for the following code I’m not looking for better alternatives.
   Also , during this test (10hrs) , website was with high traffic , iis pool did not restart!

2. Based on the following MSDN: (http://msdn.microsoft.com/en-us/library/system.timers.timer.interval.aspx)

If the interval is set after the Timer
has started, the count is reset. For
example, if you set the interval to 5
seconds and then set the Enabled
property to true, the count starts at
the time Enabled is set. If you reset
the interval to 10 seconds when count
is 3 seconds, the Elapsed event is
raised for the first time 13 seconds
after Enabled was set to true.

Is it possible that re-setting the interval in the elapsed function is the cause of the problem?

Meaning that when tTimer_Elapsed function is called the count is 1hr(min a few millisecond)
and my code “tTimer.Interval += random.Next(-5, 5);” is adding another full hour to the Interval?

Answer 1

Check this out… Jeff Atwood actually discussed something similar. I guess it worked, but according to Jeff the site outgrew this method so they went to a dedicated task.