aggregate-promise-stacks.ts

import fs from 'node:fs'
import async_hooks from 'node:async_hooks'
import process from 'node:process'
declare global {
  var promises: Record<string, number>
  var enableHook: () => {}
  var disableHook: () => {}
  var dumpPromises: () => void
}
global.promises = {}
const sourceMatchRegex = /auction-graph-api[/](src|dist)/
const hook = async_hooks
  .createHook({
    init: (_, type, __) => {
      if (type !== 'PROMISE') return
      const stack = String(new Error().stack)
      // We don't want stack frames that are exclusively in node_modules or in
      // internal node code.
      stack
        .split('\n')
        // At least one stack frame should be in our own source code.
        .filter(item => item.search(sourceMatchRegex) >= 0)
        // ... but not this very stack frame we're currently in.
        .filter(item => !item.trim().startsWith('at AsyncHook.init'))
        // If any frames are left, upsert the promises array.
        .every(_ => {
          global.promises[stack] = (global.promises[stack] || 0) + 1
          global.promises.total = (global.promises.total || 0) + 1
          // If multiple frames are in our source code, only upsert once.
          return false
        })
    },
  })
global.enableHook = () => hook.enable()
global.disableHook = () => hook.disable()
global.dumpPromises = () => {
  Object.entries(global.promises)
    // Show the total at the end.
    .filter(([key, _]) => key !== 'total')
    // Print most frequently hit stacks last.
    .sort(([_, lValue], [__, rValue]) => lValue - rValue)
    // Avoid console.log because it is async.
    .forEach(([key, value]) => fs.writeSync(1, `${key} ---> ${value}\n`))
  // Print the total.
  fs.writeSync(1, `total --> ${global.promises.total}\n`)
}