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Patterns and horizontal discovery

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Patterns and horizontal discovery

A pattern is a series of operations that tell Discovery which CIs to find on your network, what credentials to use, and what tables to populate in the CMDB.

This topic assumes you understand the phases of horizontal discovery. If you need to review the horizontal discovery process for probes and for patterns, see the following:
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.

How Discovery uses patterns

A pattern performs the same function as a probe: it identifies and explores a target CI. Discovery uses patterns only during the last two phases of discovery: Identification and Exploration.

When you kick off horizontal discovery with patterns, the Scanning and Classification phases run as they would if you were not using patterns (only using probes and sensors). After the Classification stage completes, Discovery looks at the trigger probes on the classifier to see which probe to launch. When the Horizontal Pattern probe is specified as a trigger probe, Discovery launches both the Horizontal Pattern probe and the pattern that it specifies.

Differences between probes and patterns

The main differences between using patterns for horizontal discovery and using only probes for horizontal discovery are outlined in this table:

Topic Horizontal discovery with probes Horizontal discovery with patterns
Discovery phases Probes run during all four discovery phases. Patterns run only during the identification and exploration phases. Discovery still uses the Shazzam probe and port probes to kick off discovery.
Finding new CIs

Discovery offers several out-of-box probes and sensors.

However, if you want to find new CIs or change the data that Discovery populates in the CMDB, you must create news probes and sensors or customize the existing ones. To do this, you need knowledge of Java and JavaScript, and you need to understand how probes work together with other probes and with sensors.

Discovery is offering more patterns in every major release and on the ServiceNow App Store.

If you want to create a new pattern or customize an existing one, you can use the pattern designer, which is a user-friendly interface that helps you construct steps and

Feature support Supports all standard network, and CI discovery. Certain applications are not supported without the use of patterns. See Applications supported by Service Mapping for a full list. In addition to supporting all standard discovery, patterns support:
  • Cloud discovery
  • configuration file tracking
  • CI deletion strategies
The ECC queue and troubleshooting

Discovery creates Multiple ECC Queue records depending on how many probes are launched.

To troubleshoot any issues with horizontal discovery, you must analyze several ECC queue records to see the data that Discovery retrieved.

Discovery creates only one additional ECC queue record for the pattern.

To troubleshoot any issues with horizontal discovery during identification and exploration, you only have to analyze one ECC queue record for the pattern.

Performance Depending on what type of target CI you are trying to identify and explore, Discovery might trigger multiple probes during the identification phase, and then trigger additional probes during the discovery phase. It is possible that horizontal discovery with probes can take longer because of the extra overhead in triggering and processing many probes. Discovery triggers one pattern during the identification an exploration phases. All operations that Discovery needs to run are in the pattern and Discovery can execute them in order until the pattern is finished. Therefore, pattern discovery can lead to faster performance.

Switching from probes to patterns for horizontal discovery

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, it is possible that the pattern discovery process does not synchronize on the same values that the probe discovery process does. The result could be duplicate CIs in your CMDB.

Patterns for top-down and for horizontal discovery

Both Discovery and Service Mapping can use the same pattern for horizontal and top-down discovery. But they are edited differently. See Create or modify patterns for all steps. If you take a pattern that was exclusively used for top-down discovery and you want to use it for horizontal discovery, you have to make a few modifications. See Use a pattern for horizontal discovery for instructions.