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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 enter values.

Feature support Supports all standard network, and CI discovery. Certain applications are not supported without the use of patterns. See Applications supported by Discovery and 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.

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.

Add the Horizontal Pattern probe to a classifier

To use a pattern for the identification and exploration phases of horizontal discovery, you must add the Horizontal Pattern probe to the classifiers for the CIs are you trying to discover.

Before you begin

Role required: discovery_admin

About this task

Warning: This procedure is intended for users who have not already run discovery with probes for the target CI type. If you already populated your CMDB with probe discovery and then switch to patterns, Discovery might create duplicate CIs. Follow this procedure only if you never ran Discovery with probes for the target CI type, such as Windows machines, or Citrix load balancers.

Procedure

  1. Navigate to Discovery Definition > CI Classification > {classifier type}.
  2. Open the classifier record.
  3. Click the Triggers probe related list.
  4. Deactivate the existing identification and exploration probes.
  5. Click Edit, and add the Horizontal Pattern probe. The probe appears in the related list.
  6. From the related list view, double click the field under the Pattern column and add the pattern you want to associate with the classification.
    Adding the Horizontal Pattern probe and a pattern
  7. Remove or deactivate the other probes from the Triggers probe related list.
    Note: If you delete a pattern, the Horizontal Pattern probe is not automatically removed from the classifier. You must select another pattern for the Horizontal Probe, or you can switch back to using identification and exploration probes specific to the classifier. If you use the Horizontal Probe without a pattern specified, discovery stops after the classification stage.

Use a pattern for horizontal discovery

If you want to use a new pattern, or if you already have a pattern that you were using for top-down discovery, you can use the pattern for horizontal discovery with a few modifications to the relevant classifier.

Before you begin

Role required: discovery_admin

About this task

Warning: This procedure is intended for users who have not already run discovery with probes for the target CI type. If you already populated your CMDB with probe discovery and then switch to patterns, Discovery might create duplicate CIs. Follow this procedure only if you never ran Discovery with probes for the target CI type, such as Windows machines, or Citrix load balancers.

Procedure

  1. Verify that Discovery can use the pattern:
    1. Navigate to Pattern Designer > Discovery Patterns.
    2. Open the pattern. Application patterns that Service Mapping uses are indicated as type 1-Application.
    3. In the Identification Sections on the Basic tab, verify that there is at least one section that allows for an entry point type of TCP or All. If not, create one. See the Identification steps for creating a new pattern.
    4. Save the pattern.
  2. On the instance, create or modify the classification for the CI type you want to discover. Configure the classifier as follows:
    1. Navigate to Discovery Definition > CI Classification > {classification type}.
    2. Open the relevant classifier.
    3. Configure the classifier as follows:
      • Relationship type: Select Runs on::Runs (for process classifiers only)
      • Condition: Configure the same condition you defined in the pattern.
      • Triggers probes Related list: Add the Horizontal Pattern probe, and then add the pattern you are using to the Pattern column.
    See Create a Discovery CI classification for a description of the other fields on the classifier.

What to do next

Run the pattern in Debug mode to test it. When you are sure the pattern works, you can run discovery by setting up a discovery schedule or running an on-demand discovery. See Schedule a discovery for more information.

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