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 optimizes how agents connect to MID Servers by enabling each agent to select the most efficient MID Server based on connectivity factors such as latency and current load. This feature, part of the Agent Client Collector (ACC), is disabled by default and is designed to streamline MID Server management and improve connection efficiency without requiring manual URL configuration updates on the agent host.

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    Key Features

    • Connectivity-Based Selection: Agents test connectivity to available MID Servers and choose the best connection considering latency and the number of connected agents.
    • Fail-Over Mechanism: Agents maintain a primary and secondary MID Server list for automatic fail-over if a connection is lost.
    • Dynamic Updates: ServiceNow instances periodically send updated MID Server lists to agents to keep configurations current.
    • Security Integration: Communication between MID Servers and agents is secured using the MID Server unified key store.
    • Capability-Based Selection: MID Servers are configured with Agent Client Collector capabilities to ensure agents only select eligible MID Servers.

    Considerations for Use

    • Automatic MID Server selection functions as a fail-over mechanism rather than a true load balancer; for load balancing, an application load balancer may be more appropriate.
    • Complexity increases due to multiple input sources determining back-end URLs, unlike single URL configuration with a load balancer.
    • Agents receive a list of all ACC-capable MID Servers, which may include those in restricted zones, potentially triggering security alerts.
    • DNS resolution used for selection can produce unexpected results; this should be evaluated especially in environments with frequent network changes (e.g., VPN, Wi-Fi switches).
    • End User Compute systems that switch networks may face reconnection challenges due to IP address changes.
    • MID Servers can be explicitly excluded from agent selection to address firewall or security constraints.

    Practical Application for ServiceNow Customers

    ServiceNow customers looking to improve agent-to-MID Server connections can enable automatic MID Server selection to reduce manual configuration efforts and dynamically optimize connectivity. Before enabling, evaluate your network architecture, DNS setup, and security policies to ensure the feature aligns with your environment and does not introduce connection or security issues. Configure MID Server capabilities properly and exclude any MID Servers that should not be accessible by agents. Use this feature primarily as a fail-over mechanism rather than a load balancer, or consider integrating an application load balancer if load distribution is required.

    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.