Tracium

Tracium is the Google Lighthouse tracing parser extracted into a stand-alone library.

Tracium is a modern alternative to Big Rig. Tracium correctly parses modern Chrome Traces (generated by Chrome 66+).

Usage

Install:

$ npm install tracium

Use:

const Tracium = require('tracium');
const traceJSON = JSON.parse(fs.readFileSync('./mytrace.json', 'utf8'));
const tasks = Tracium.computeMainThreadTasks(traceJSON, {
  // |flatten| default to |false|. When false, only top-level tasks will be returned.
  flatten: true,
});

Check out examples at //examples/ folder.

API

tracium.computeMainThreadTasks(traceJson[, options])

• traceJson <Object> A JSON of a Chromium trace
• options <Object> Set of options for trace processing
  • flatten <boolean> Defaults to false. Whether to flatten tasks tree.
• returns: <Array<Object>> An array of tasks:
  • kind <string> describes task attribution. Can be one of the following:
    • 'parseHTML'
    • 'styleLayout'
    • 'paintCompositeRender'
    • 'scriptParseCompile'
    • 'scriptEvaluation'
    • 'garbageCollection'
    • 'other'
  • startTime <number> monotonic start time in milliseconds
  • endTime <number> monotonic end time in milliseconds
  • duration <number> task duration in milliseconds, a.k.a. "wall time"
  • selfTime <number> time spent in the task at the current level of the task tree
  • event <Object> original trace event object associated with the task
  • children <Array<[Task]>> an array of child tasks
  • parent <?[Task]> a parent task if any

Returns an array of tasks that belong to the main thread of the inspected page. If flatten is passed to false, than only top-level tasks will be returned.

An example task

{
  event:
   { pid: 29772,
     tid: 775,
     ts: 588826692280,
     ph: 'X',
     cat: 'toplevel',
     name: 'TaskQueueManager::ProcessTaskFromWorkQueue',
     args:
      { src_file: '../../base/trace_event/trace_log.cc',
        src_func: 'SetEnabled' },
     dur: 27,
     tdur: 22,
     tts: 514358 },
  startTime: 0,
  endTime: 0.027,
  children: [],
  duration: 0.027,
  selfTime: 0.027,
  kind: 'other' }