Horizontal discovery process flow with patterns

  • Release version: Xanadu
  • Updated August 1, 2024
  • 2 minutes to read
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    Summary of Horizontal discovery process flow with patterns

    The horizontal discovery process with patterns in ServiceNow streamlines configuration item (CI) discovery by using patterns instead of multiple probe sets during the later phases. This method is divided into four phases: Scanning, Classification, Identification, and Exploration. The first two phases use probes, while the last two phases leverage patterns to efficiently discover and update the CMDB.

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    Scanning phase

    • Discovery initiates with the Shazzam probe and port probes, which are placed in the External Communication Channel (ECC) queue.
    • The MID Server retrieves these probes and runs them against the host to identify open ports using protocols such as WMI, HTTP, SSH, and SNMP.
    • Open ports detected (e.g., port 22 indicating a UNIX/Linux machine) help classify the device type.

    Classification phase

    • Based on the port probe results, Discovery sends a classification probe via the ECC queue.
    • The MID Server runs this classification probe to gather detailed information like the operating system version.
    • This information determines the CI class, with only one classification probe used per device.

    Identification and Exploration phases

    • These phases are unified through patterns instead of separate probes.
    • Discovery selects the appropriate classifier and launches the corresponding horizontal pattern probe, which contains a sensor responsible for updating the CMDB.
    • Patterns require applicative credentials for discovering applications running on hosts, in addition to host access credentials.
    • The pattern operations specify the necessary identification and exploration actions, with Discovery performing inserts or updates to the CMDB accordingly.
    • Only the Horizontal Discovery Sensor is used in these phases; other probes and sensors are not involved.

    Practical implications for ServiceNow customers

    • This approach improves discovery efficiency by reducing reliance on multiple probe sets in later phases.
    • Ensuring proper configuration of both host and application credentials is critical for successful discovery using patterns.
    • Understanding this flow aids in troubleshooting and optimizing discovery processes in your ServiceNow environment.

    Horizontal discovery with patterns has four phases, just as horizontal discovery with probes does. However, for the last two phases, Discovery triggers operations from a pattern, rather than additional sets of probes.

    Scanning phase

    1. Discovery first takes the Shazzam probe (and then port probes) and places it in a request in the External Communication Channel (ECC) queue.
    2. The MID Server checks the ECC queue, retrieves the discovery request, and runs the probes against the host and discovers open ports.
    3. The port probes scan common ports using several protocols, such as WMI, HTTP, SSH, and SNMP.
    4. If one or more ports respond, the Shazzam probe sends information about the port back to the ECC queue through the MID Server.
    5. Discovery checks the ECC queue to find out which ports responded, which identifies the type of machine. For example, if Shazzam detects that the machine is listening on port 22, Discovery treats the machine as a UNIX or Linux machine.

    Classification phase

    1. The Discovery application determines which classification probe to send to the newly discovered device by using information in the record of the port probe that successfully responded.
    2. Discovery puts the classification probe into the ECC queue.
    3. The MID Server checks the ECC queue, retrieves the discovery request, and runs the classification probe.
    4. The classification probe retrieves additional information, such as which version of the operating system is running on a machine. This information determines the class of the CI that Discovery found. There is only one classification probe per discovered device.
    5. The classification probe sends information back to the instance ECC queue through the MID Server.

    The Identification and Exploration phases

    Patterns unify the Identification and Exploration phases of discovery.

    1. Discovery determines which classifier to use based on the class of the CI and the criteria specified in all CI classifier records. The classifier specifies the Horizontal Pattern probe, which in turn specifies which pattern to launch. The Horizontal pattern probe also contains a sensor which does the actual work of updating the CMDB.
      Note:
      Patterns need applicative credentials to find applications running on host machines. Make sure you have applicative credentials configured along with the credentials required to access the host machine itself.
    2. The operations in the pattern specify the actions that Discovery needs to take for both the identification and exploration phases. Discovery knows which identification rules to use based on the CI type in the pattern, and Discovery makes inserts or updates to the CMDB based on these rules. Only the Horizontal Discovery Sensor is used. Other probes and sensors are not used.