Identifying related alerts in log data by using log correlators

  • Release version: Zurich
  • Updated July 31, 2025
  • 2 minutes to read
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    Summary of Identifying related alerts in log data by using log correlators

    Log correlators in ServiceNow's Zurich release enable you to detect relationships between alerts in log data, helping to determine if an alert is part of a larger issue. By analyzing keys or values within log entries, correlators identify patterns across multiple alerts, improving incident understanding and resolution.

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    Key Features

    • Types of Log Correlators:
      • Free Text Correlators: Analyze the message portion of log lines to find specific terms (e.g., “policy-id,” “thread-id,” or unique service names like “TeaTime”) that indicate related alerts across various components.
      • Log Property Correlators: Analyze metadata fields such as service instance names, interface IDs, or request IDs to detect correlations in alerts from different log sources.
    • Scope Configuration: You can specify which log sources a correlator applies to:
      • Only new log sources created after correlator activation
      • All log sources
      • Specific log source(s) you define
    • Customization: You can define custom correlators to tailor detection to your unique environment and business context, enhancing alert correlation accuracy.
    • Excluding Sources: You can exclude specific log sources from analysis by a correlator to avoid irrelevant or noisy correlations.

    Practical Benefits for ServiceNow Customers

    Using log correlators helps you quickly identify related alerts in complex environments, reducing alert noise and enabling faster root cause analysis. Whether by detecting shared identifiers in metadata or unstructured text terms unique to your services, correlators enhance visibility into interconnected issues. Customization options and source exclusions provide flexibility to adapt correlation logic to your operational needs.

    Log correlators are keys or values in log data that detect correlations between alerts to help you determine whether an alert is part of a larger issue. For example, a log correlator could detect when the interface ID of a particular network device occurs simultaneously in multiple warnings across different service instances.

    You can identify related alerts in your log data by using log correlators. The base system includes several log correlators, and you can define custom correlators for a specific log source, all log sources, or only log sources created after the correlator is activated.

    Most log lines include a metadata portion plus a message portion. Some log lines, however, include only message text with metadata included in the text. The two types of log correlators, free text correlators and log property correlators, analyze the different portions of each log to identify relationships between log data from multiple log sources.

    Free text correlators

    Free text correlators analyze the text within the log message portion of log lines that are associated with an anomaly. The system uses free text correlators to identify correlations between alerts. You use free text correlators to add a term that you expect to appear within log messages. A good choice is a term that is not structured and would not otherwise be extracted as a log property. For example, “policy-id” or “ thread-id”.

    You also typically add free text correlators for the names of systems, applications, and services that are unique to your environment. Because such a value can be referred to by multiple sources, layers, middleware, or databases, the free text correlator can be an effective detector of correlated alerts. For example, if your organization's service is called TeaTime, then you might add "teatime" as a free text correlator. The correlator would identify alerts that are related because they were generated for resources that support the TeaTime service, such as a database lock or a connection failure between TeaTime components.

    Log property correlators

    Log property correlators analyze the metadata portion of log lines. For example, the correlator can analyze the name of a service instance, the interface ID of a network device, or the request ID of a web-facing component. A log property correlator could flag a correlation when the interface ID of a network device simultaneously occurs in multiple warnings in different log sources. Log property correlators are specific to the business context of your environment.

    You can specify the set of log sources whose log data are analyzed by a log correlator. Choices are as follows:
    • Only new sources: The system applies the log correlator only to log lines from log sources that were created after this log correlator is activated.
    • All sources: The system applies the log correlator to log lines from all log sources.
    • Specified source: For a log correlator, the system analyzes only log lines from the log source that you specify.