Schedule detectors

The schedule detector is a time-based detector. A schedule detector detects whether the system clock is equal to or greater than a specific date and/or time. For example, you could log an event every week on Monday at 2:00 p.m.

Schedule detectors are different from other detectors in that they are real-time detectors. The value of the system clock is checked every second. Schedule detectors are very fast and can be used without great concern about efficiency. Thus, a schedule detector provides the only real-time event processing. However, there is no guarantee of when the action will occur.

All of the schedule detectors that you set up are handled by a dedicated scheduling thread. This allows for a separation between the processing load needed to execute schedule detectors and the processing load needed to perform all of the other event work. The scheduling thread will maintain a list of detection times in a time queue. If you add a schedule detector, the thread will register the detection time in the queue and then re-sort the list of all detection times from the earliest to the latest.

The time of the system clock is then compared with the time of the first item in the schedule queue. If the system clock time is equal to or greater than the time of the first item, the detection algorithm for the first item will be invoked and the detection will be performed.

The Classic Event subsystem does not account for Daylight Savings Time changes. If you set up a schedule detector that runs periodically with a specified start time, you will need to change the start time to reflect the time change. Another solution would be to use the time-weighted average retrieval mode instead of the Classic Event subsystem to generate averages, because the retrieval mode handles the Daylight Savings Time changes. However, if the period for the average is hourly, then it is recommended that you use the Classic Event subsystem, as the amount of data will not generally not be a factor in the speed of calculating the average.