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content-tracing

The content-trace module is used to collect tracing data generated by the underlying Chromium content module. This module does not include a web interface so you need to open chrome://tracing/ in Chrome browser and load the generated file to view the result.

var tracing = require('content-tracing');
tracing.startRecording('*', tracing.DEFAULT_OPTIONS, function() {
  console.log('Tracing started');

  setTimeout(function() {
    tracing.stopRecording('', function(path) {
      console.log('Tracing data recorded to ' + path);
    });
  }, 5000);
});

tracing.getCategories(callback)

  • callback Function

Get a set of category groups. The category groups can change as new code paths are reached.

Once all child processes have acked to the getCategories request, callback is called back with an array of category groups.

tracing.startRecording(categoryFilter, options, callback)

  • categoryFilter String
  • options Integer
  • callback Function

Start recording on all processes.

Recording begins immediately locally, and asynchronously on child processes as soon as they receive the EnableRecording request. Once all child processes have acked to the startRecording request, callback will be called back.

categoryFilter is a filter to control what category groups should be traced. A filter can have an optional - prefix to exclude category groups that contain a matching category. Having both included and excluded category patterns in the same list would not be supported.

Examples:

  • test_MyTest*,
  • test_MyTest*,test_OtherStuff,
  • "-excluded_category1,-excluded_category2

options controls what kind of tracing is enabled, it could be a OR-ed combination of tracing.DEFAULT_OPTIONS, tracing.ENABLE_SYSTRACE, tracing.ENABLE_SAMPLING and tracing.RECORD_CONTINUOUSLY.

tracing.stopRecording(resultFilePath, callback)

  • resultFilePath String
  • callback Function

Stop recording on all processes.

Child processes typically are caching trace data and only rarely flush and send trace data back to the browser process. That is because it may be an expensive operation to send the trace data over IPC, and we would like to avoid much runtime overhead of tracing. So, to end tracing, we must asynchronously ask all child processes to flush any pending trace data.

Once all child processes have acked to the stopRecording request, callback will be called back with a file that contains the traced data.

Trace data will be written into resultFilePath if it is not empty, or into a temporary file. The actual file path will be passed to callback if it's not null.

tracing.startMonitoring(categoryFilter, options, callback)

  • categoryFilter String
  • options Integer
  • callback Function

Start monitoring on all processes.

Monitoring begins immediately locally, and asynchronously on child processes as soon as they receive the startMonitoring request.

Once all child processes have acked to the startMonitoring request, callback will be called back.

tracing.stopMonitoring(callback);

  • callback Function

Stop monitoring on all processes.

Once all child processes have acked to the stopMonitoring request, callback is called back.

tracing.captureMonitoringSnapshot(resultFilePath, callback)

  • resultFilePath String
  • callback Function

Get the current monitoring traced data.

Child processes typically are caching trace data and only rarely flush and send trace data back to the browser process. That is because it may be an expensive operation to send the trace data over IPC, and we would like to avoid much runtime overhead of tracing. So, to end tracing, we must asynchronously ask all child processes to flush any pending trace data.

Once all child processes have acked to the captureMonitoringSnapshot request, callback will be called back with a file that contains the traced data.

tracing.getTraceBufferPercentFull(callback)

  • callback Function

Get the maximum across processes of trace buffer percent full state. When the TraceBufferPercentFull value is determined, the callback is called.

tracing.setWatchEvent(categoryName, eventName, callback)

  • categoryName String
  • eventName String
  • callback Function

callback will will be called every time the given event occurs on any process.

tracing.cancelWatchEvent()

Cancel the watch event. If tracing is enabled, this may race with the watch event callback.