trace_events

• function createTracing(

  options: CreateTracingOptions

  ): Tracing;

  Creates and returns a Tracing object for the given set of categories.

  import trace_events from 'node:trace_events';
  const categories = ['node.perf', 'node.async_hooks'];
  const tracing = trace_events.createTracing({ categories });
  tracing.enable();
  // do stuff
  tracing.disable();
  
• function getEnabledCategories(): undefined | string;

  Returns a comma-separated list of all currently-enabled trace event categories. The current set of enabled trace event categories is determined by the union of all currently-enabled Tracing objects and any categories enabled using the --trace-event-categories flag.

  Given the file test.js below, the command node --trace-event-categories node.perf test.js will print 'node.async_hooks,node.perf' to the console.

  import trace_events from 'node:trace_events';
  const t1 = trace_events.createTracing({ categories: ['node.async_hooks'] });
  const t2 = trace_events.createTracing({ categories: ['node.perf'] });
  const t3 = trace_events.createTracing({ categories: ['v8'] });
  
  t1.enable();
  t2.enable();
  
  console.log(trace_events.getEnabledCategories());
  

Type definitions

• interface CreateTracingOptions

  • categories: string[]

    An array of trace category names. Values included in the array are coerced to a string when possible. An error will be thrown if the value cannot be coerced.

• interface Tracing

  The Tracing object is used to enable or disable tracing for sets of categories. Instances are created using the trace_events.createTracing() method.

  When created, the Tracing object is disabled. Calling the tracing.enable() method adds the categories to the set of enabled trace event categories. Calling tracing.disable() will remove the categories from the set of enabled trace event categories.

  • readonly categories: string

    A comma-separated list of the trace event categories covered by this Tracing object.

  • readonly enabled: boolean

    true only if the Tracing object has been enabled.

  • disable(): void;

    Disables this Tracing object.

    Only trace event categories not covered by other enabled Tracing objects and not specified by the --trace-event-categories flag will be disabled.

    import trace_events from 'node:trace_events';
    const t1 = trace_events.createTracing({ categories: ['node', 'v8'] });
    const t2 = trace_events.createTracing({ categories: ['node.perf', 'node'] });
    t1.enable();
    t2.enable();
    
    // Prints 'node,node.perf,v8'
    console.log(trace_events.getEnabledCategories());
    
    t2.disable(); // Will only disable emission of the 'node.perf' category
    
    // Prints 'node,v8'
    console.log(trace_events.getEnabledCategories());
    
  • enable(): void;

    Enables this Tracing object for the set of categories covered by the Tracing object.