The ECC queue for Discovery

  • Release version: Xanadu
  • Updated August 1, 2024
  • 3 minutes to read
    • Summarize
    Summarized using AI
    This content was generated using new OpenAI-powered functionality. Results are provided on an as is basis and are not guaranteed to be accurate or complete.

    Summary of The ECC queue for Discovery

    The External Communication Channel (ECC) Queue acts as the communication bridge between your ServiceNow instance and integrated systems, primarily the MID Server, during IT Asset Discovery. It holds records representing messages exchanged between the instance and target systems, tracking probe and sensor activities along with their XML payloads.

    Show full answer Show less

    Contents and Usage

    ECC queue records are categorized as output (instructions from the instance to the target system) or input (responses from the target system to the instance). These records enable a connected view of the discovery process, offering insight into data collection and asset targeting.

    Automatic Deletion and Retention

    Because the ECC queue can grow substantially during discovery runs, completed task records are automatically deleted after 7 days by default. However, it is recommended to retain ECC queue data for at least a month to facilitate troubleshooting, such as investigating probe data discrepancies. You can customize deletion schedules and table rotations for the ECC queue using settings for eccqueueevent and eccqueue tables.

    Accessing the ECC Queue

    You can view ECC queue records via the following navigation paths:

    • Discovery > Output and Artifacts > ECC Queue
    • ECC > Queue

    Records include details like probe instructions, processing states, and XML payloads, which are valuable for understanding and troubleshooting discovery tasks.

    ECC Queue Record States and Processing

    Records transition through states such as ready, processing, processed, and error during discovery:

    • Output records start as ready when probe instructions are created, progress to processing as the MID Server executes them, and finally to processed.
    • Input records follow a similar state flow as responses from the MID Server are processed.
    • Error states indicate issues during processing and serve as key starting points for troubleshooting discovery failures.

    Debugging and Customization

    For advanced troubleshooting, you can use the script debugger on the session processing the ECC queue payloads, reviewing the business rules and scripts involved. Additionally, discovery sensor behavior regarding ECC queue attachments can be controlled via properties:

    • Save ECC queue attachments: By default, sensor attachments are deleted after processing; enabling this property preserves them for debugging purposes.

    This property is configurable under Discovery Definition > Properties.

    The External Communication Channel (ECC) Queue is a connection point between your ServiceNow instance and other systems that integrate with it, most commonly a MID Server.

    Contents of the ECC Queue

    The ECC queue contains records that are created during all stages of discovery. Each record is a message from the instance to system your are targeting for discovery, classified as output, or a message from that system to the instance, classified as input.

    ECC queue records provide you with a connected flow of probe and sensor activity along with the XML payload sent to or from an instance and the assets you are targeting.

    Automatic deletion of ECC queue records

    As your IT Asset Discovery runs, the size of the ECC queue can grow to several gigabytes. Most of the “completed tasks” records are unnecessary, but some might be important for troubleshooting any problems.

    For example, if Discovery is not properly capturing the disk drives on a particular Windows server, you can look in the ECC Queue at the data returned by the Windows - System Information probe. For this reason, you should retain ECC Queue data from Discovery for at least a month.

    By default, records in the ECC Queue older than 7 days are deleted automatically. You can set the deletion schedule by updating the ECC queue (as we will explain in the next section) and the table rotation schedule. The table rotation names are:
    • ecc_queue_event
    • ecc_queue

    Accessing the ECC queue

    You can access the ECC queue from either of these locations:
    • Discovery > Output and Artifacts > ECC Queue
    • ECC > Queue

    The following image is an example of a record in the ECC queue. This record shows that a WMI classifier probe was instructed to run and has been processed. Note the XML payload it returned as the discovery task collected data. See The MID Server ECC queue for a description of each field.

    Figure 1. An example ECC queue record
    An example ECC Queue

    ECC queue states

    Input and output messages keep processing until the discovery is finished or terminated. You can monitor the ECC queue to see records populate during discovery and see the states of each record change.

    ECC queue input records are processed by business rules (BR), but not all business rules direct these ECC queue inputs to process. As a result, some ECC queue inputs remain in a ready state.

    The process is as follows:
    1. When new probe instructions are available for the MID Server, the system creates an output record with the state of ready.
    2. The MID Server then starts processing the probe instructions and the state changes to processing before it finally changes to processed.
    3. When a result returns to the MID Server and is ready to be sent to the instance, the system creates an input record with the state of ready.
    4. While the system processes the payload, the state changes to processing before it finally changes to processed.

      If any errors are encountered, the state changes to error. You can review errors as a starting point for troubleshooting a failed discovery.

    Debug processing of ECC queue records

    To use a script debugger, process the payload on the same session as the debugger. Review the business rule which processes the particular ECC queue record and the actual code which processes the payload.

    Properties and parameters that affect the ECC queue

    These properties are available to control aspects of the ECC queue:
    Property Description
    Save ECC queue attachments The normal behavior for discovery sensors is to delete attachments to ECC queue entries upon successful sensor processing. Enabling this property overrides this behavior, and forces attachments to be preserved. This is typically done for debugging purposes.

    To enable this property, navigate to Discovery Definition > Properties.