The Track Gap Detector Processor can be used to detect the absence of events from streaming data. Like Incident Detector, GeoEvents sent from Track Gap Detector are not copies (or derivatives) of GeoEvents received by the processor. GeoEvents sent from the processor are associated with the TrackGap GeoEvent Definition created when GeoEvent Server is installed.
GeoEvents sent to a Track Gap Detector Processor must have a GeoEvent Definition with a TRACK_ID. The processor uses this tagged field to determine when GeoEvents are no longer being received. A processor must receive at least one GeoEvent with a given TRACK_ID before it will be able to detect the absence of GeoEvents for that track.
With the Track Gap Detector Processor, you must specify both the Gap Duration and Gap Detection Interval:
- Gap Duration specifies the number of seconds the processor will wait before determining expected data has not been received.
- Gap Detection Interval specifies the number of seconds in each polling interval.
For example, assuming a Track Gap Detector Processor is configured with a gap detection interval of 120 seconds and a gap duration of 300 seconds, the processor would check its internal register of received GeoEvents every two minutes (120 seconds) to see if any TRACK_ID in its registry had not been observed within the last five minutes (300 seconds).
The gap detection interval also controls how often notifications are generated. When the notification mode is set to Continuous, a new TrackGap event will be generated on each poll of the processor's internal registry for each TRACK_ID expected but not recently received. If you prefer a single notification when a gap is first detected, followed by a second event to notify you when the expected GeoEvents are once again being received, specify the On Change notification mode.
Finally, when configuring a Track Gap Detector Processor you can specify the GeoEvent field that contains the geometry. If a GeoEvent field name is specified, the processor will append the geometry from the most recently received GeoEvent to TrackGap events it generates. For example, if a data stream was reporting the position of vehicles and the processor was configured to poll every 30 seconds to determine if a gap of at least 120 seconds existed since the last received vehicle report, the processor could be configured to include the last reported vehicle location with its gap notification events.