/// <summary>
/// <see cref="TimerCallback"/> to be called every tick. Checks validity of the tick, performs workload and schedues the next tick.
/// </summary>
/// <param name="state"></param>
private static void OnTick(object state)
{
Logger.LogTick();
DateTime now = DateTime.Now;
// Recalculate next run dates if the last tick was more than 90 seconds ago or if it is in the future.
// Such clock skew implies manual time change, huge NTP leap, machine awakened from hibernation/suspension or some other potentially unsafe state.
if (now - _lastTick > _skewLimit || now < _lastTick)
{
Logger.LogTickSkew();
foreach (Task task in Config.Tasks.Values)
{
task.RefreshNextRunDate();
}
LogCleaner.Start();
LogCleaner.RefreshNextRunDate();
}
else
{
DoTick(now);
}
// The next tick time has to be readjusted often to maintain the precision of the scheduled tasks.
// System.Threading.Timer is ridiculously imprecise. The best case scenario skews the timer by 1 ms per minute (1 minute per ~100 days).
// An alternative would be to create a custom timer implementaion based on high-precision multimedia timers, but
// System.Threading.Timer is simple to use and guaranteed to be supported pretty much everywhere, so it's good enough.
SetNextTick(now);
}
/// <summary>
/// Logs the values and tasks present in <see cref="Config"/>.
/// </summary>
public static void LogConfig()
{
if (Writer != null)
{
Log(string.Format("[Config] Got log retention period {0} days", Config.LogRetention));
LogCleaner.RefreshNextRunDate(); // Produces log cleaner log line
foreach (Task task in Config.Tasks.Values)
{
task.RefreshNextRunDate(); // Produces task detail log line
}
}
}
/// <summary>
/// Performs workload during normal tick. Runs <see cref="Task"/> or <see cref="LogCleaner"/> if they are scheduled to be run in the current tick.
/// </summary>
/// <param name="now"></param>
private static void DoTick(DateTime now)
{
foreach (Task task in Config.Tasks.Values)
{
if (task.NextRunDate <= now)
{
task.Start();
task.RefreshNextRunDate();
}
}
if (LogCleaner.NextRunDate <= now)
{
LogCleaner.Start();
LogCleaner.RefreshNextRunDate();
}
}