debugging-aid/inprogress/leak2.js

Experimental tools for debugging Node.js apps without pausing

'use strict'

const inspector = require('inspector')
const session = new inspector.Session()

const iliketoleakyleaky = {
  myspoon: 'my spoon is too big'
}

let collectable = {
  ishallbe: 'collected!'
}

const {
  Worker,
  isMainThread,
  parentPort,
  workerData
} = require('worker_threads')

if (isMainThread) {
  mainThread()
} else {
  worker()
}

function mainThread () {
  const worker = new Worker(__filename)
  worker.on('message', console.log)
  worker.on('error', console.error)

  session.connect()
  let started = false

  session.on('HeapProfiler.addHeapSnapshotChunk', (m) => {
    if (!started) {
      worker.postMessage({ command: 'start' })
      started = true
    }
    worker.postMessage({ command: 'chunk', chunk: m.params.chunk })
  })

  session.post('HeapProfiler.takeHeapSnapshot', null, (err, r) => {
    worker.postMessage({ command: 'end' })
    started = false

    console.log('HeapProfiler.takeHeapSnapshot done:', err, r)
    collectable = { newnewnew: 'stuffstuff' }
    session.post('HeapProfiler.takeHeapSnapshot', null, (err, r) => {
      worker.postMessage({ command: 'end' })
      started = false
      console.log('HeapProfiler.takeHeapSnapshot done:', err, r)
      session.disconnect()
    })
  })
}

function worker () {
  let previous, current, currentString

  const logic = () => {
    console.log(current)
    // reformat to extract meaningful data
    // diff
    // find largest items
    // extract and save
  }

  const commands = {
    start (message) {
      previous = current
      current = null
      currentString = ''
    },
    chunk (message) {
      currentString += message.chunk
    },
    end (message) {
      current = JSON.parse(currentString)
      logic()
    }
  }
  parentPort.on('message', (message) => {
    commands[message.command](message)
  })
}