debugging-aid/hooks.js

Experimental tools for debugging Node.js apps without pausing

'use strict'
const asyncHooks = require('async_hooks')
const { performance } = require('perf_hooks')
const { cleanHooksStackMeta } = require('./lib/cleanStack')
const { printMessage } = require('./lib/print')
const filePath = process.env.AID_HOOK_SCOPE

const data = new Map()
const depthCache = {}
function getDepthFor (asyncId, triggerAsyncId) {
  const value = (depthCache[triggerAsyncId] || 0) + 1
  depthCache[asyncId] = value
  return value
}
function getFunctionId (stack, asyncId) {
  // debugLog(cleanHooksStack(stack))
  const meta = cleanHooksStackMeta(stack)
  if (meta.untraceable) {
    return null
  }
  let clean = meta.frames[0]
  if (clean.split('(')[1][0] !== '/') {
    printMessage(`COULD NOT PROCESS STACKTRACE ${asyncId} ${stack.split('\n').slice(2).join('\n')}`)
  }
  if (meta.wasAnon) {
    clean = meta.wasAnon + clean
  }
  if (meta.wasConsole) {
    clean = '    at console called' + clean
  }
  return clean.replace('    at ', '')
}
Error.stackTraceLimit = Math.max(Error.stackTraceLimit, 20)
const asyncHook = asyncHooks.createHook({
  init (asyncId, type, triggerAsyncId) {
    const e = {}
    Error.captureStackTrace(e)
    if (data.has(triggerAsyncId) || e.stack.includes(filePath)) {
      const funcId = getFunctionId(e.stack, asyncId)
      if (funcId) {
        data.set(asyncId, { funcId, triggerAsyncId, depth: getDepthFor(asyncId, triggerAsyncId) })
      }
    }
  },

  before (asyncId) {
    const info = data.get(asyncId)
    if (!info) return

    performance.mark('b' + asyncId)
  },

  after (asyncId) {
    const info = data.get(asyncId)
    if (!info) return

    performance.mark('a' + asyncId)
    const prefix = ' '.repeat(info.depth - 1) + '└'
    printMessage(`${prefix}[${denominate(info.triggerAsyncId)}->${denominate(asyncId)}] ${info.funcId}`)
    performance.measure(`[${denominate(asyncId)} from ${denominate(info.triggerAsyncId)}] ${info.funcId}`, 'b' + asyncId, 'a' + asyncId)
  }
// TODO add destroy to clean up data in case node reuses sayncIds
})

let first = 0
function denominate (num) {
  if (!first) {
    first = parseInt(num, 10) - 1
  }
  return pad(num - first)
}

function pad (num) {
  if (num < 10) return '00000' + num
  if (num < 100) return '0000' + num
  if (num < 1000) return '000' + num
  if (num < 10000) return '00' + num
  if (num < 100000) return '0' + num
  return num
}

asyncHook.enable()