MID Server selection

  • Release version: Xanadu
  • Updated August 1, 2024
  • 7 minutes to read
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    Summary of MID Server selection

    MID Server selection in ServiceNow enables precise control over which MID Server is assigned to perform tasks such as Discovery, Orchestration, Service Mapping, Event Management, and Cloud Management. Selection can be based on application association, IP address ranges, network capabilities, or specific behaviors. This flexibility ensures that MID Servers are optimally utilized and aligned with organizational and network requirements. Additionally, domain separation can be used to restrict MID Server scope within specific domains.

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    Key Features

    • Selection Modes:
      • Auto-select MID Server: Automatically chooses a suitable MID Server based on status and criteria, supporting failover and load balancing.
      • Use specific MID Server cluster: Limits selection to members of a specified cluster, with failover and load balancing based on cluster type.
      • Use specific MID Server: Assigns a particular MID Server explicitly; no automatic reassignment occurs if it is down.
    • Selection Criteria:
      • Application: MID Servers are tagged with supported applications (e.g., Discovery, Orchestration, Service Mapping), including an ALL option.
      • IP Address or Range: MID Servers are configured with allowed IP ranges; applications specify target IPs to match these ranges.
      • Capabilities: Network capabilities required by applications (e.g., PowerShell for Orchestration) must match those configured on the MID Server.
      • Behaviors: Used only by Discovery and Service Mapping to define port scan methods; not applicable to other applications or auto-selection.
    • Domain Separation: MID Servers can be assigned to specific domains to restrict their availability for users within those domains, enhancing security and management.
    • Selection Testing: Service Mapping provides a MID Server selection test to preview which MID Server will be used for a given IP, application, and capability.

    How Applications Select MID Servers

    If no specific MID Server is designated, applications select MID Servers based on application, IP range, and capability criteria as follows:

    • Discovery: Requires Discovery or ALL application on the MID Server; IP ranges on schedules and MID Servers must align.
    • Orchestration: Requires Orchestration or ALL application; target IP and required capabilities must match MID Server settings.
    • Service Mapping: Requires Service Mapping or ALL application; endpoint IP and supported capabilities must match.
    • Event Management: Requires Event Management or ALL application; event connector IP must fall within MID Server IP range.
    • Cloud Management: Requires Cloud Management or ALL capability; no IP or application criteria apply.

    Practical Considerations

    • When using specific MID Servers, if the selected MID Server is down or unvalidated, the application will not execute commands.
    • Default MID Servers serve as fallback options when auto-selection fails to find eligible MID Servers.
    • For Orchestration involving resources within defined IP ranges, mapping fully-qualified domain names (FQDN) to IP addresses is necessary for certain activities.
    • Overrides can be configured to customize MID Server selection beyond the default criteria.

    You can configure MID Server selection by application, IP address ranges, network capability, or behavior. Specific MID Servers can be assigned to particular tasks, or the MID Server can be selected automatically. MID Servers can use domain separation to limit the scope of discoveries and event management.

    Setup indicator for configuration phaseEnsure that the MID Server can connect to elements inside and outside your networkDownload and install the MID Server on a Linux or Windows hostConfigure your MID ServerConfigure MID Server securityEnsure that the MID Server can connect to elements inside and outside your networkDownload and install the MID Server on a Linux or Windows hostConfigure your MID ServerConfigure MID Server security

    The MID Selector used by most applications has three modes to select a MID Server:

    • Auto-select MID Server: Selects from MID Servers based on MID Server criteria, regardless of whether they are members of a cluster.
    • Use specific MID Server: Automatic reassignment to another MID Server is not supported.
    • Use specific MID Server cluster: Automatic reassignment to another MID Server only selects from members of the specified cluster.

    For Agent Client Collector, refer to Automatic MID Server selection.

    MID Server criteria

    MID Servers offer these types of criteria that help an application determine which MID Server to use:
    • Application: The application that you specify on the MID Server. You can designate these applications for a specific MID Server:
      • Discovery
      • Orchestration
      • Service Mapping
      • Event Management
      • Operational Intelligence
      • Cloud Management
      An ALL application option is also available. By default, this option includes all applications. You can configure which applications are included in the ALL designation.
    • IP address or range: The IP address or the IP ranges that the MID Server is allowed to work within. You can specify an IP address or IP range in the application, such as on a Discovery schedule or an Orchestration activity, and for the MID Server. If the IP configured in the application matches the IP address or falls within the allowable IP range configured on the MID Server, a match is possible, and that MID Server passes this criteria. To have the instance automatically assign IP ranges (subnets) to available MID Servers, see Using MID Server IP range auto-assignment.
    • Capabilities: The network capability an application needs to use, such as the PowerShell Orchestration activity or the Workflow Studio PowerShell step. Some applications, like Cloud Management, require a specific capability.
      Note:
      Discovery and Service Mapping can also use behaviors, which determine the type of port probes used during the port scan phase of Discovery. Both Discovery and Service Mapping use a behavior to discover Create a discovery behavior for Unix-based load balancers. Other applications do not use behaviors. Behaviors are not used for auto-selection, default MID Servers, or specific MID Servers as described below. See Discovery behaviors for more information.

    How an application selects a MID Server

    If you do not specify a specific MID Server for an application to use, the application tries to select one. Each application relies on different criteria to select an appropriate MID Server.
    Application Supported Application on the MID Server IP address range Capability
    Discovery

    (Select Auto-Select MID Server on the Discovery schedule)

    		 The Discovery or ALL application must be specified on the MID Server. Discovery uses IP ranges that you configure on the Discovery Schedule form to see if they fall within the IP ranges that you configure on the MID Server, or the ALL IP ranges option must be selected on the MID Server. N/A
    Note:
    Any configured behaviors are ignored.
    Orchestration The Orchestration or ALL application must be specified on the MID Server. The target IP address that you configure in an Orchestration activity must fall within the IP ranges that you configure on the MID Server, or the ALL option must be selected on the MID Server. The capability that is required for an Orchestration activity must match the capabilities you configure on the MID Server, or the MID Server capability must be set to ALL.
    Service Mapping The Service Mapping or ALL application must be specified on the MID Server. The endpoint IP address must fall within the IP range that you configure on the MID Server, or the ALL option must be selected on the MID Server.

    One of the supported Service Mapping capabilities (for new installs) must be configured on the MID Server, or the MID Server capability must be set to ALL.

    Event Management The Event Management or ALL application must be specified on the MID Server. The IP configured in the event connector instances, such as Configure event collection from HPOM, must fall within the IP range configured on the MID Server.
    Cloud Management N/A N/A The Cloud Management or ALL capability must be added.

    Mode: Auto-select MID Server

    During initial work assignment to a MID Server, or when failing over existing work from a down MID Server to another MID Server, the MID selector picks a set of suitable MID from a given status level by traversing the steps below once. If at any step it finds at least one server, all remaining steps are skipped.

    1. Suitable MID Servers with status = Up.

    2. Default MID Server (if it was defined) with status = Up.

    3. Suitable MID Servers with status = Upgrading or Paused.

    4. Default MID Server (if it was defined) with status = Upgrading or Paused.

    5. Suitable MID Servers with status = Upgrade Failed, Draining, Drained, Drain Failed, or Down.

    6. Default Mid Server (if was defined).

    All steps which are below an application's minimum status level are skipped. Many applications (such as Discovery) allow Up or Degraded MID Servers, other applications only allow Up MID Servers.

    Mode: Use specific MID Server cluster

    During initial work assignment to a MID Server, or when failing over existing work from a down MID Server to another MID Server, the MID selector picks a set of suitable MID from a given status level by traversing the steps below once. If at any step it finds at least one server, all remaining steps are skipped.

    1. Suitable Mid Servers with status = Up.

    2. Suitable Mid Servers with status = Upgrading or Paused.

    3. Suitable Mid Servers with status = Upgrade Failed, Draining, Drained, Drain Failed, or Down.

    All steps which are below an application's minimum status level are skipped. Many applications (such as Discovery) allow Up or Degraded MID Servers, other applications only allow Up MID Servers.

    A MID server is picked from set of MID servers at the highest status level as follows depending on cluster type:

    • Load Balance Cluster: picks a MID Server within the status level randomly.

    • Fail-over Cluster: picks a MID Server with best cluster records' order number (0 = best).

    Mode: Use a specific MID Server

    Discovery and Event Management can use a MID Server that you specifically call out.

    Note:
    Selecting a specific MID Server is not the same as specifying the default MID Server for an application. A specific MID Server is always used. If it is Down or not validated, the application does not execute commands against the MID Server. A default MID Server is fallback that is used when the auto-selection of MID Servers does not find any eligible MID Server.
    Application How you specify a specific MID Server Criteria that the default MID Server must meet
    Discovery Choose the MID Server on the Discovery schedule.
    Note:
    You can also specify a cluster of MID Servers.
    		 If you select a MID Server without the Discovery or ALL application, it automatically adds the Discovery application.
    Orchestration N/A N/A
    Service Mapping N/A N/A
    Event Management Choose one or more MID Servers on the connector instance event collection, such as Configure event collection from HPOM. N/A
    Cloud Management N/A N/A
    Note:
    If a MID Server manages resources within defined IP ranges for Orchestration, you must map the fully-qualified domain name (FQDN) of a server with its IP address to run certain activities, such as Exchange activities.

    Domain separation

    If you are using domain separation, you can configure MID Servers to be in separate domains. The domain that the MID Server is in affects how the application selects the domain:

    Discovery and Service Mapping: On the Discovery schedule, the MID Servers and clusters that available for selection are limited to the same domain of the user who is configuring the schedule. This also applies to the auto-selection option: only MID Servers in the same domain as the user can be automatically selected.

    MID Server selection test for Service Mapping

    If Service Mapping is active, you can preview which MID Server that Service Mapping uses for a specific target device or computer. To do this, navigate to Service Mapping > MID Servers and click MID Selection Test. Enter the IP address and an optional application and capability, and then click OK. The name of the MID Server that Service Mapping will use appears in the window.

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