protected override void OnDoWork(DoWorkEventArgs e)
{
_logger.Info("Worker started.");
DateTime lastTime = TimekeeperClock.Now();
DateTime timeNow;
_next = _timetable.GetNextEntry(lastTime);
_logger.DebugFormat("Next timetable entry is at {0} in {1}", _next.ScheduledTime, _next.TimeUntil);
while (!CancellationPending)
{
Thread.Sleep(100);
timeNow = TimekeeperClock.Now();
if ( Math.Abs( (timeNow - lastTime).Ticks ) > TimeSpan.FromMinutes(1).Ticks)
{
//if the time changes more then one minute (plus or minus)
//after a 1/10 of a second sleep, then
//we've had some kind of major clock adjustment (potentially daylight savings time)
//so recalculate what the next entry would be
//have to back up the time a bit, in case it went from 1:59:59am to 3:00:01am on dst change
_logger.InfoFormat("Clock drift detected from {0} to {1} in one cycle.", lastTime, timeNow);
DateTime lookBackTime = timeNow.Add(TimeSpan.FromMinutes(-1));
_logger.InfoFormat("Recalculating next entry based on a time of {0}", lookBackTime);
_next = _timetable.GetNextEntry(lookBackTime);
}
if (_next.PastTime)
{
//time to execute
_logger.DebugFormat("{0} is after {1}, executing tasks for timetable entry.", TimekeeperClock.Now(), _next.ScheduledTime);
ExecuteTasksAsync(_next);
_next = _timetable.GetNextEntry(timeNow);
_logger.DebugFormat("Next timetable entry is at {0} in {1}", _next.ScheduledTime, _next.TimeUntil);
}
//reset last time
lastTime = timeNow;
}
//cancellation pending, so exit out
e.Cancel = true;
_logger.Info("Cancellation pending, worker stopped.");
}
private void ExecuteTasksAsync(TimetableEntry entry)
{
foreach (var task in entry.Tasks)
{
//avoid the closure!
var taskToExecute = task;
_logger.DebugFormat("Queueing task {0} in thread pool.", taskToExecute.FriendlyName);
ThreadPool.QueueUserWorkItem(state =>
{
try
{
var result = taskToExecute.Execute(entry.ScheduledTime);
var worker = (TimekeeperWorker)state;
worker.ReportCompleted(taskToExecute, result);
}
catch (Exception e)
{
//do not reference the scheduler instance to avoid closure
var worker = (TimekeeperWorker)state;
if (!worker.ReportException(taskToExecute, e)) throw;
}
}, this);
}
}