@dnlup/doc

doc

Get usage and health data about your Node.js process

• Installation
• Usage
• API
  • Doc([options])
    • events
      • data

Installation

$ npm i @dnlup/doc

Usage

const Doc = require('@dnlup/doc');

const doc = Doc(); // Use the default sample interval
doc.on('data', data => {
  doStuffWithCpuUsage(data.cpu)
  doStuffWithMemoryUsage(data.memory)
  doStuffWithEventLoopDelay(data.eventLoopDelay)
  doStuffWithGarbageCollectionDuration(data.gc)
})

API

Doc([options])

Create a new Doc instance with the given options.

• options: Object. Optional. Configuration object
• options.sampleInterval: Number. Optional. Sample interval (ms), each sampleInterval ms a data event is emitted. On Node 10 the default value is 500 while on Node >= 12 is 1000. Under the hood the package uses monitorEventLoopDelay where available to sample the event loop and this allows to increase the default sample interval on Node >= 12.
• options.eventLoopOptions: Object. Optional. Options to setup monitorEventLoopDelay

events

data

Process data event.

Properties:

Name	Description
eventLoopDelay	Event loop delay (ms)
memory	Object containing memory usage stats
memory.rss	RSS memory (bytes)
memory.heapTotal	Total heap Memory (bytes)
memory.heapUsed	Heap memory used (bytes)
memory.external	Extarnal memory (bytes)
cpu	Cpu usage percentage
gc	Object containing garbage collection stats
gc.major	average duration (ms) of perf_hooks.constants.NODE_PERFORMANCE_GC_MAJOR*
gc.minor	average duration (ms) of perf_hooks.constants.NODE_PERFORMANCE_GC_MINOR*
gc.incremental	average duration (ms) of perf_hooks.constants.NODE_PERFORMANCE_GC_INCREMENTAL*
gc.weakCB	average duration (ms) of perf_hooks.constants.NODE_PERFORMANCE_GC_WEAKCB*
raw	Object containing raw values
raw.cpu	Object containing the raw values returned from process.cpuUsage()
raw.eventLoopDelay	Raw representation of the event loop delay, on Node 10 it is the delay in nanoseconds, on Node >= 12 is a Histogram instance

• *: the average duration of garbage collection statistics may be undefined if no garbage collection occurred within the sampleInterval

Changelog

1.2.0-0 (2020-07-03)

Features

• use PerformanceObserver for gc stats (fae15d2)

Bug Fixes

• gc types are number | undefined (fae1cf4)
• split gc into separate file to make testing easier (fae108f)