Automatic MID Server selection

  • Release version: Zurich
  • Updated July 31, 2025
  • 2 minutes to read
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    Summary of Automatic MID Server selection

    Automatic MID Server selection in the Agent Client Collector (ACC) feature enables each agent to connect with the most efficient available MID Server by performing connectivity tests based on latency and current load. This feature is disabled by default and is designed to optimize agent-to-MID Server connections without manual configuration of back-end URLs.

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    Use Case Considerations

    • Benefits: Automatically narrows down MID Server options based on capabilities, keeps back-end URL configurations updated on agents, and improves connection efficiency through latency and load assessment.
    • Limitations: This is a fail-over mechanism rather than a true load balancer, leading to higher complexity in back-end URL determination. Using an application load balancer may be simpler in some scenarios.
    • Security Concerns: Agents receive a list of all MID Servers, including those in restricted areas, which could trigger security alerts if they attempt connections.
    • Network Considerations: DNS resolution is periodic and might cause connection issues for End User Compute systems frequently switching networks (e.g., corporate, Wi-Fi, VPN).

    Automatic MID Server Selection Process

    Once enabled, the ServiceNow instance periodically updates agents with a list of available MID Servers. Agents select primary and secondary MID Servers from this list, storing the information in their configuration files to enable fail-over if the primary connection fails. Agents also automatically re-select the optimal MID Server if their IP address changes. Secure communication between agents and MID Servers is maintained using the MID Server unified key store.

    Enabling and Configuring Automatic MID Server Selection

    • Enable automatic MID Server selection to allow agents to assess connectivity and choose the best MID Server based on latency and load.
    • Configure MID Servers with Agent Client Collector capabilities so that agents can identify eligible servers for automatic selection.
    • Explicitly configure any MID Servers that should be excluded from agent connections, for example due to firewall restrictions.

    Practical Impact for ServiceNow Customers

    By enabling automatic MID Server selection, customers can reduce manual configuration and maintenance efforts for agent connections, optimize resource usage, and enhance fail-over capabilities. However, customers should weigh the complexity and potential security implications, especially in environments with restricted MID Servers or dynamic network contexts.

    Automatic selection of MID Servers ensures that each agent uses the most efficient available MID Server.

    The Agent Client Collector automatic MID Server selection feature set is disabled by default. There are several factors to consider before determining if automatic MID Server selection is right for your use cases.

    Use case considerations

    Automatic MID Server selection provides several benefits. MID Server capabilities can narrow the list of MID Servers an agent can potential connect to. Automatic MID Server selection keeps the back-end URL configuration list up to date on the agent host without additional work flows.

    When automatic MID Server selection is enabled, the agent performs a connectivity test against the list of available MID Servers and determines the best connection based on latency and number of currently connected agents.

    However, there are several additional considerations that may make automatic MID Server selection wrong for your use case.

    The ACC automatic MID Server selection is not a true load balancer and should be considered a fail-over mechanism. There is higher complexity for choosing a back-end URL as it is derived from multiple input sources. If, instead, an application load balancer is used only one back-end URL needs to be specified. See Enable the Agent Client Collector load balancer for more information.

    By default, each agent is sent the list of all MID Servers listening for ACC connections. Since that list includes MID Servers running in restricted areas, the agents can try to connect to them which can generate security alerts.

    Your DNS configuration should be considered before using automatic MID Server selection because the resolution can lead to unexpected results. The DNS resolution is done periodically. End User Compute systems that alternate between internal corporate, Wi-Fi, VPN, or external networks may not be able to reconnect if the network context has changed.

    Automatic selection process

    When automatic selection is enabled, the ServiceNow instance sends periodic MID Server updates to existing agents. The agent selects a MID Server based on information it receives from the ServiceNow instance.

    During automatic MID Server selection, the agent selects a primary MID and a secondary MID list, and writes them to the agent’s config file. The agent uses this list for fail-over protection when the primary MID/secondary MID in the list loses connection.

    When an agent detects that its IP address has changed, it automatically connects with the most efficient MID Server available from the agent's list of MID Servers.

    To secure communication between the MID Server and the agent, use the MID Server's unified key store. For details on using the MID Server unified key store, see MID Server unified key store.