Watchdog are use to follow if detectors involved in the scan have the right behavior. For that you need to register on a Scan a callback class inherited from WatchdogCallback.

WatchdogCallback

This callback has 4 possible methods:

• .on_scan_new called we the scan starts
• .on_scan_end called at the end of the scan
• .on_scan_data called when new data is emitted by the scan.
• .on_timeout called basically when the watchdog timed out.

.on_scan_data

In this method you may follow if data received are what you expect. i.e: check if detectors received all trigger. In case of a detector’s misbehavior, you can raise an exception. All exception will bubble-up except the StopIteration which is treated as a normal stop.

.on_timeout

Timeout callback is called if no other event happen between the watchdog_timeout. i.e: if no more data are received and we reach the watchdog_timeout. If you want to stop the scan, you need to raise an exception like in .on_scan_data.

Note

In the constructor of this class, you can specify the watchdog_timeout which is the minimum calling time of the method .on_timeout of this class.