Script Debugger and Session Log

  • Release version: Yokohama
  • Updated January 30, 2025
  • 3 minutes to read
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    Summary of Script Debugger and Session Log

    The Script Debugger in ServiceNow Yokohama release enables users with thescriptdebuggerrole to debug server-side JavaScript interactively. Meanwhile, users with thelogdebuggerrole can view and download session logs. These tools provide detailed control over script execution and logging, facilitating efficient debugging of business rules, script includes, UI actions, and other server-side scripts.

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    Key Features

    • Script Debugger Capabilities:
      • Dedicated debug transactions limited to the current session.
      • Set, remove, and manage breakpoints and conditional breakpoints.
      • Pause execution at breakpoints and step through code line-by-line, including stepping into/out of functions.
      • Evaluate expressions and modify variables during runtime using the Console.
      • View call stacks, local/global variables, private variables from closures, and transaction details.
      • Support for multiple developers debugging their own transactions simultaneously without interference.
      • Impersonation support allows debugging as another user if appropriate roles and permissions are present.
      • Integration with domain separation to control data and access boundaries during debugging.
    • Session Log Capabilities:
      • Users with logdebugger role can access session logs for business rules, script includes, and UI components like ServiceNow Agent Workspace.
      • Logs can be viewed in a separate tab and downloaded as needed.
      • Configurable limits on the number of transactions and messages shown, with defaults at 100 transactions and 10,000 messages.
      • Options to specify debug output visibility via the glide.debugger.log.ui system property.
    • Additional Functionalities:
      • Script execution pauses only on interactive transactions where GlideSystem.isInteractive() returns true.
      • Console caches executed statements per browser session, configurable via user preferences, enhancing debugging efficiency.
      • Script Tracer helps filter and identify changed script lines during execution, improving problem isolation.
      • Scripts run in interpreted mode; scripts in strict mode are not supported by the debugger.

    Practical Usage and Configuration

    • Launch the Script Debugger from the application navigator, Studio, or syntax editor for immediate debugging.
    • Use breakpoints and logpoints to control script execution flow and console output.
    • Configure user preferences such as glide.debugger.log.transaction.count and glide.debugger.logmessageslimit to adjust logging thresholds.
    • Enable or customize the Session Log tab display via the glide.debugger.log.ui system property to suit your interface preferences.
    • Note that Scripts - Background module does not support direct breakpoint setting but allows debugging of invoked script objects.

    Benefits for ServiceNow Customers

    These debugging tools empower developers to efficiently troubleshoot and optimize server-side scripts by providing granular control over script execution and comprehensive logging capabilities. This leads to faster issue resolution, improved script quality, and enhanced productivity in maintaining ServiceNow applications.

    The Script Debugger enables users with the script_debugger role to debug server-side JavaScript. Users with the log_debugger role can use the Session Log to view and download required logs.

    Users with the script_debugger role can perform these actions using Script Debugger:
    • Have a dedicated debug transaction, which applies only to the current session.
    • Set and remove breakpoints.
    • Pause the current session at a breakpoint.
    • Evaluate expressions during runtime.
    • Step through code line-by-line.
    • Step into and out of function and method calls.
    • View the value of local and global variables.
    • View the value of private variables from function closures.
    • View the call stack.
    • View the transaction that the system is processing.
    • Turn off the script debugger to resume running paused scripts.
    Use the Session Log tab to retrieve the session log for business rules, script includes, and a custom UI such as ServiceNow® Agent Workspace that has a GraphQL component. Users with the log_debugger role can:
    • View session logs in a separate tab.
    • Download a log.
    • View logs for Agent Workspace.
    • Specify debug options to view or download only the required logs.
    By default, 100 transactions and 10,000 messages appear on the Session Log tab. If the transaction or message count exceeds the default value, the session log is cleared and the next transactions or messages appear. You can configure this transaction and message count using the glide.debugger.log.transaction.count and glide.debugger.log_messages_limit user preferences respectively. For more information about the glide.debugger.log.transaction.count and glide.debugger.log_messages_limit user preferences, see User preference settings.
    Note:
    Enable Session Log as a separate tab with Script Debugger using the glide.debugger.log.ui system property.
    • The Page option displays logs under forms and lists and on the Session Log tab.
    • The Session option displays logs only on the Session Log tab.

    For more information about the glide.debugger.log.ui system property, see Available system properties.

    When you execute a statement in the Console, the executed statement is stored in the browser cache. You can use the up arrow key to get the previous statement and down arrow key to get the next statement from the browser cache. The user preference setting, glide.debugger.console.cached_stmt_limit, defines the number of statements cached in a browser session. The default statement cache value is 20 and the maximum value is 100. You can configure the statement cache value from user preferences.

    Note:
    The cached statements are not available when the browser cache is cleared or when you log in from a different browser or a different computer.
    The Script Debugger can pause any server-side script that runs in an interactive transaction such as business rules, script includes, script actions, or UI actions that require a response to proceed. If the GlideSystem method isInteractive() returns True when running the script in context, then the Script Debugger can pause it.
    Note:
    Some script objects, such as script includes, can be called from multiple contexts. For example:
    • when a business rule runs a script include on a form submit that is an interactive transaction waiting on the form data to change before continuing.
    • when a scheduled job runs the same script include that is a non-interactive background transaction that can also run other scripts simultaneously.

    To debug client-side scripts, you can use browser-based developers tools.

    A debugger transaction remains open as long as the user session is valid. If a user logs out or their session times out, the system closes the debugger transaction.

    To view debug logs, see Display debugging logs.

    Note:
    When the Script Debugger is enabled, code is executed in interpreted mode. If parts of the script are set to run in strict mode, the debugger is not able to find the correct objects and the debugger fails. The Script Debugger must run on scripts outside of strict mode.