node/doc/api/tracing.markdown

Tracing

Stability: 1 - Experimental

The tracing module is designed for instrumenting your Node application. It is not meant for general purpose use.

Be very careful with callbacks used in conjunction with this module

Many of these callbacks interact directly with asynchronous subsystems in a synchronous fashion. That is to say, you may be in a callback where a call to console.log() could result in an infinite recursive loop. Also of note, many of these callbacks are in hot execution code paths. That is to say your callbacks are executed quite often in the normal operation of Node, so be wary of doing CPU bound or synchronous workloads in these functions. Consider a ring buffer and a timer to defer processing.

require('tracing') to use this module.

v8

The v8 property is an EventEmitter, it exposes events and interfaces specific to the version of v8 built with node. These interfaces are subject to change by upstream and are therefore not covered under the stability index.

Event: 'gc'

function (before, after) { }

Emitted each time a GC run is completed.

before and after are objects with the following properties:

{
  type: 'mark-sweep-compact',
  flags: 0,
  timestamp: 905535650119053,
  total_heap_size: 6295040,
  total_heap_size_executable: 4194304,
  total_physical_size: 6295040,
  used_heap_size: 2855416,
  heap_size_limit: 1535115264
}

getHeapStatistics()

Returns an object with the following properties

{
  total_heap_size: 7326976,
  total_heap_size_executable: 4194304,
  total_physical_size: 7326976,
  used_heap_size: 3476208,
  heap_size_limit: 1535115264
}