Performance of the system.threading.timers in windows service

Question

I have developed the windows service in C#.NET . In this, I have used system.threading.timer .
when i have start the 10 second interval timer there is some variation between the execution timing.
//code
public void SetTimers(int timer, DataRow row)
{
TimeSpan dueTime;
TimeSpan interval;
SetTimeIntervals(row, out dueTime, out interval); timer1[timer] = new System.Threading.Timer(databaseTrensfer, row, dueTime, interval);
}
public void databaseTrensfer()
{
//code
}
private void SetTimeIntervals(DataRow row, out TimeSpan tsDueTime, out TimeSpan tsPeriod)
{
string alarmType = Convert.ToString(row["EBase"]);
string EType = Convert.ToString(row["EType"]);
string EFrequency = Convert.ToString(row["EFrequncy"]);
if (alarmType == "Milisecond")
{
int frquency1 = Convert.ToInt32(row["Tfrquency"]);
tsDueTime = new TimeSpan(0, 0, 0, 0, frquency1);//frquency1=interval
tsPeriod = new TimeSpan(0, 0, 0, 0, frquency1);
}
else if (alarmType == "Second")
{
int frquency1 = Convert.ToInt32(row["Tfrquency"]);
tsDueTime = new TimeSpan(0, 0, 0, frquency1);
tsPeriod = new TimeSpan(0, 0, 0, frquency1);
}
else if (alarmType == "Once")
{
tsDueTime = new TimeSpan(0, 0, 0);
tsPeriod = new TimeSpan(0, 0, 0);
}
else if (alarmType == "Minute")
{
int frquency1 = Convert.ToInt32(row["Tfrquency"]);
tsDueTime = new TimeSpan(0, frquency1, 0);
tsPeriod = new TimeSpan(0, frquency1, 0);
}
else if (alarmType == "Hour")
{
int minute = 0;
int frquency1 = 1;
if (Convert.ToString(row["RelativeFactor"]) != "")
minute = Convert.ToInt32(row["RelativeFactor"]);
if (Convert.ToString(row["Tfrquency"]) != "")
frquency1 = Convert.ToInt32(row["Tfrquency"]);
tsDueTime = new TimeSpan(frquency1, minute, 0);
tsPeriod = new TimeSpan(frquency1, 0, 0);
}
else
{
tsDueTime = new TimeSpan();
tsPeriod = new TimeSpan();
}
}
i have pass the frequency to set the timer & start the number of timer simultaneously
my o/p
2011-08-22 13:42:08.0
2011-08-22 13:42:18.0
2011-08-22 13:42:28.0
2011-08-22 13:42:38.15
.
.
.
2011-08-22 14:28:38.984
2011-08-22 14:28:48.984
2011-08-22 14:28:59.15
2011-08-22 14:29:09.15
2011-08-22 14:29:19.15
.
.
2011-08-22 15:14:59.953
2011-08-22 15:15:09.968
2011-08-22 15:15:19.968
i got this o/p timer started at the 08 seconds of variation then shifting to the 09 second
why all timers are not executing in exact timing?
thanks in advance

Vulpes · Answer

The following attempts to resynchronize the timer with the system clock after each interval of a second or longer has elapsed. The code is 'off the top of my head' and so might not be quite right: // add these fields private TimeSpan[] _interval; private DateTime[] _startTime; // when you create timer1 array need to initialize the above arrays int len = timer1.Length; _interval = new TimeSpan[len]; _startTime = new DateTime[len]; // change SetTimers method as follows; public void SetTimers(int timer DataRow row) { TimeSpan dueTime; TimeSpan interval; SetTimeIntervals(row out dueTime out interval); _interval[timer] = interval; _startTime[timer] = DateTime.Now + dueTime; object[] obj = new object[2]{row timer}; timer1[timer] = new System.Threading.Timer(databaseTrensfer obj dueTime interval); } // change databaseTrensfer method as follows public void databaseTrensfer(object state) { object[] obj = (object[])state; DataRow row = (DataRow)obj[0]; string alarmType = Convert.ToString(row[EBase]); if (alarmType != Milisecond && alarmType != Once) { int timer = (int)obj[1]; DateTime dt = DateTime.Now; long elapsedMs = Convert.ToInt64((dt - _startTime[timer]).TotalMilliseconds); long intervalMs = Convert.ToInt64(_interval[timer].TotalMilliseconds); long remainder = elapsedMs % intervalMs; if (remainder != 0L) { timer1[timer].Change(_interval[timer] - TimeSpan.FromMilliseconds(remainder) _interval[timer]); } } //code }

vrushali katkade · Answer

Thanks a lot... it's working fine

vrushali katkade · Answer

what is the procedure of the resynchronizing the timer with the system clock every minute ?

Vulpes · Answer

Well the resolution of the System.Threading.Timer is about 10 to 20 ms so I don't think it's an accuracy problem as such. However the operation of the timer may be affected by what else is running on the machine. The TimerCallback method runs on a threadpool thread and if other processes are making heavy use of the CPU and/or threadpool obtaining a thread from the pool or a time-slice for that thread at the exact time it's needed may be difficult. If the loss of accuracy is a problem I'd try resynchronizing the timer with the system clock every minute say.