Discovery probes and sensors

Discovery phases

Discovery always uses probes and sensors during the first two phases of discovery: scanning and classification. For the last two phases, identification and exploration, Discovery can use probes and sensors or patterns. This topic refers to probes and sensors only. See Discovery basics for an explanation of these phases. See Patterns and horizontal discovery for more information on patterns.

Probes, sensors, and the ECC queue

The probe collects the information and the sensor processes it. Both get their instructions from the ECC queue. There is a worker job on the MID Server that monitors the queue for work. The monitor checks for any entries where the Queue is output and the State is ready.

The MID Server then processes all the output ECC messages, runs the necessary probes, and returns the probes results to the ECC queue. These results are put in the ECC Queue as input entries.

After an entry is inserted in the ECC Queue table, a business rule fires (on insert) that takes that information and runs it through a sensor processor. The sensor processor's job is to take the input data, find any sensors interested in that data, and pass it along to be processed. Those sensors ultimately update the CMDB.

How probes and sensors work together

The MID Server launches probes to collect information about a device. The probe sends back information to the sensor to be processed. If the probe has a post-processing script defined, the post-processing script does some data processing on the MID Server before data is sent back to the sensor on the ServiceNow instance. Otherwise the probes sends back all the data collected and the sensor performs this data processing. In both cases, the sensor updates the CMDB.

A multi-probe is a probe that contains probes. A multi-sensor processes the data from a multi-probe. To process the data from the multi-probe, the multi-sensor contains individual scripts to process the data returned by each probe contained in the Multiprobe, as well as a main multi-sensor script. The individual scripts pass their processed data to the main multi-sensor script.

Probe types