@sematext/gc-stats

Note!

This is a fork of dainis/node-gcstats. I did not write the code nor claim I have. I'm only maintaining the dependencies that are required for my own open-source projects. Repos I maintain that need gc-stats to work:

• https://github.com/sematext/sematext-agent-express
• https://github.com/sematext/spm-agent-nodejs
• https://github.com/sematext/spm-agent

GCStats

Exposes stats about V8 GC after it has been executed.

Usage

Create a new instance of the module and subscribe to stats-events from that:

var gc = (require('gc-stats'))();

gc.on('stats', function (stats) {
    console.log('GC happened', stats);
});

This will print blobs like this whenever a GC happened:

GC happened {
  startTime: 9426055813976,
  endTime: 9426057735390,
  pause: 1921414,
  pauseMS: 1,
  gctype: 1,
  before: {
     totalHeapSize: 11354112,
     totalHeapExecutableSize: 3670016,
     usedHeapSize: 7457184,
     heapSizeLimit: 1501560832,
     totalPhysicalSize: 9725880,
     totalAvailableSize: 1488434544,
     mallocedMemory: 8192,
     peakMallocedMemory: 1186040
  },
  after: {
     totalHeapSize: 12402688,
     totalHeapExecutableSize: 3670016,
     usedHeapSize: 6485792,
     heapSizeLimit: 1501560832,
     totalPhysicalSize: 10166144,
     totalAvailableSize: 1489388528,
     mallocedMemory: 8192,
     peakMallocedMemory: 1186040
  },
  diff: {
     totalHeapSize: 1048576,
     totalHeapExecutableSize: 0,
     usedHeapSize: -971392,
     heapSizeLimit: 0,
     totalPhysicalSize: 440264,
     totalAvailableSize: 953984,
     mallocedMemory: 0,
     peakMallocedMemory: 0
  }
}

Property insights

• totalHeapSize: Number of bytes V8 has allocated for the heap. This can grow if usedHeap needs more.
• usedHeapSize: Number of bytes in use by application data
• total HeapExecutableSize: Number of bytes for compiled bytecode and JITed code
• heapSizeLimit: The absolute limit the heap cannot exceed
• totalPhysicalSize: Committed size (node 0.11+)
• totalAvailableSize: Available heap size(node 4+)
• startTime: Nanoseconds for start, using hrtime()
• endTime: Nanoseconds for end, using hrtime()
• pause: Nanoseconds from start to end of GC using hrtime()
• pauseMS: pause expressed in milliseconds
• mallocedMemory
• peakMallocedMemory
• numberOfNativeContexts
• numberOfDetachedContexts
• gctype can have the following values(v8 source):
  • 1: Scavenge (minor GC)
  • 2: Mark/Sweep/Compact (major GC)
  • 4: Incremental marking
  • 8: Weak/Phantom callback processing
  • 15: All

Installation

npm install gc-stats

Node version support

node-gcstats depends on C++ extensions which are compiled when the gc-stats module is installed. Compatibility information can be inspected via the Travis-CI build jobs.

Changelog

1.5.2

20 October 2020

• ci: add nodejs_version: 14 #46
• Test on node 13 in linux, upload prebuilt binaries #47
• fix(deps): ran npm audit fix and updated mocha version #43
• small improvement in example.js #38
• update dependencies for node 12 #37
• Update node-pre-gyp to solve issues with node 10 and lerna #32
• expose startTime and endTime #24
• Remove duplicate line from README.md #20
• Replace constructor w/ Singleton; Use bindings module; #17
• Explain where version compatibility information can be located #14
• Test against recent Node releases #13
• Add Travis CI badge #12
• Thanks #9
• update nan to v1.7.0 #5
• Add info on GC type and expand README info #4
• Add some help to the README. #2
• Fix #35, use round for ms #35
• Fix #27, update node-pre-gyp #27
• Use uv_async for work scheduling(fix #22) and add few more fields to stats #22
• Fixed #1, now it will use Nan package for v8 stuff, so hopefully no more breakages with new versions #1
• added release it 57a223c
• Update dependencies 906f87e
• #36 update nan so that it compiles on node 12 97fd32d