Understanding Pattern-Based Discovery in ServiceNow Blog

[Prathmeshda]

With increasingly complex and dynamic IT environments, the classic approach to Discovery, which relies on probes and sensors, is undergoing change. ServiceNow has launched Pattern Operations, a new and improved approach to exploring your Configuration Items (CIs). In this blog, we'll take a journey into the world of Pattern Operations and examine how they work, why they are better, and how they revolutionize the process of Discovery.

What are Patterns?
A Pattern in ServiceNow Discovery is a set of operations that instructs the system
on which CIs to look for, using which credentials, and how to fill which tables in
the CMDB. Unlike traditional probes and sensors, which are coded in JavaScript,
patterns are coded in the Neebula Discovery Language (NDL) and can be customized
using the Pattern Designer.

The Power of Pattern Operations
Pattern Operations are the discrete actions within a pattern that complete specific
tasks. Pattern Operations enable a very granular and accurate discovery process.
Key Pattern Operations
. Set Parameter Value: This operation is used to set variables that will be used
later in the pattern.
. Parse Variable: This operation pulls specific information from a command’s
output, such as a version number from a text string.
. Run Command: This operation runs a shell command (over SSH) or a WMI
query on the target host.
. Insert/Update CI: This is the final operation where the gathered information is
written to the correct CMDB table.
. Conditionals (If/Else): This operation enables the pattern to make decisions
based on the information it discovers (for example, if it discovers a Linux server,
run this command; if it discovers a Windows server, run that command)

How Patterns are Triggered
In the horizontal discovery process, patterns are involved after the Scanning and Classification phases.
Classification Probe: After the classification of a device, the classifier initiates the Horizontal Pattern Probe.
Pattern Launcher: The probe initiates the particular pattern identified by the classifier.
Pattern Operations: The pattern carries out a series of operations to discover and explore the CI.

Advantages of Using Patterns
Unified Discovery: Discovery and identification are done by one pattern,
which means fewer probes are sent to the network.
No Scripting Required: The Pattern Designer enables administrators to design
and modify discovery logic without needing to write complex scripts.
Faster Troubleshooting: The Pattern Designer enables administrators to view a
“Step-by-Step” execution, which helps administrators understand where a
discovery is failing.
Extensibility: It is easy to extend existing patterns to discover new attributes or
new application types.

Conclusion
Pattern Operations are the future of ServiceNow Discovery. With Pattern Operations, you have a more flexible, visual, and efficient way of exploring your IT infrastructure. Patterns give you the power to have a more accurate CMDB with less work. Whether you are discovering cloud infrastructure or legacy on-premises infrastructure, Pattern Operations are essential to a successful ITOM strategy.

If you found this article useful, please mark it as Helpful. It helps others find the content more easily 👍

[VijayKan]

Thank you @Prathmeshda for sharing this info.
It looks just in time for a topic I've been searching for documentation on NDL if any.  Apparently, there is still none published by ServiceNow.
https://www.servicenow.com/community/developer-forum/documenation-on-ndl-for-discovery-patterns/m-p/...

The following page, 
https://www.servicenow.com/docs/r/it-operations-management/discovery-and-service-mapping-patterns/t_...

refers to a KB
https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB1698521, and it has a PDF attachment describing more in detail of creating or customizing patterns.

It is still obscure to understand, why relevant information is not maintained on the main documentation portal for easier reference.