Discovery probes and sensors
perform data collection and update the CMDB.
Note: With each release, patterns are replacing many probes and sensors for Discovery.
Consider creating new patterns or editing existing ones if you want to customize what
Discovery can find. The information on probes and sensors is intended for customers who
are not using patterns yet and for customers who already have customized probes that are
retained upon upgrade. See
Patterns and horizontal discovery for more information on
patterns.
Warning: DO NOT switch from probes to
patterns if you are already running Discovery with probes, and your CMDB is already
populated. If you do so, it is possible that the pattern Discovery process does not
synchronize on the same values that the probe Discovery process does. This could result in
duplicate CIs in your CMDB.
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.
Figure 1. ECC queue input
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
| Device |
Probe Type |
| Windows computers and
servers |
Remote WMI queries, shell commands |
| UNIX and Linux servers |
Shell command (via SSH protocol, version 2). Discovery supports any Bourne-compatible
shell. |
| Storage |
CIM/WBEM queries |
| Printers |
SNMP queries |
| Network gear (switches, routers, etc.) |
SNMP queries |
| Web servers |
HTTP header examination |
| Uninterruptible Power Supplies (UPS) |
SNMP queries |
