nodejs 应用火焰图简单分析

以前有写过一个使用speedscope 的简单说明，以下是一个使用另外一个工具进行火焰图分析的简单说明

环境准备

• 项目结构

├── app.js

├── package.json

└── yarn.lock

• 代码说明
  app.js

 

//app.js

const express = require('express');

const console = require('console');

const levenshtein = require('fast-levenshtein');

var arr=[];

const HOW_OBVIOUS_THE_FLAME_GRAPH_SHOULD_BE_ON_SCALE_1_TO_100 = 10;

​

const someFakeModule = (function someFakeModule () {

return {

  calculateStringDistance (a, b) {

    return levenshtein.get(a, b, {

    useCollator: true

    })

  }

 }

})()

​

const app = express();

​

app.get('/', (req, res) => {

  res.send(`

  <h2>Take a look at the network tab in devtools</h2>

  <script>

    function loops(func) {

    return func().then(_ => setTimeout(loops, 20, func))

    }

    loops(_ => fetch('api/tick'))

  </script>\

  `)

});

​

app.get('/api/tick', (req, res) => {

  arr.push({name:'Shubham'});

  Promise.resolve('asynchronous flow will make our stacktrace more realistic'.repeat(HOW_OBVIOUS_THE_FLAME_GRAPH_SHOULD_BE_ON_SCALE_1_TO_100))

  .then(text => {

    const randomText =Math.random().toString(32).repeat(HOW_OBVIOUS_THE_FLAME_GRAPH_SHOULD_BE_ON_SCALE_1_TO_100)

    return someFakeModule.calculateStringDistance(text, randomText)

  })

  .then(result => res.end(`result: ${result}, ${arr.length}`))

});

​

app.get('/api/end', () => process.exit());

​

app.listen(8080, () => {

  console.log(`go to http://localhost:8080/ to generate traffic`)

});

pacakge.json

{

  "name": "nodejs-flame-graph",

  "version": "1.0.0",

  "main": "app.js",

  "license": "MIT",

  "scripts": {

    "start": "node --perf-basic-prof-only-functions app.js",

    "pprof":"node --prof app.js",

    "flame":"node --prof-process --preprocess -j isolate*.log | flamebearer"

  },

  "dependencies": {

    "express": "^4.14.1",

    "fast-levenshtein": "^2.0.6"

  },

  "devDependencies": {

    "flamebearer": "^1.1.3"

  }

}

启动&&测试

• 启动集成prof

yarn pprof

• 一些压力测试

ab -n 2000 -c 100 http://localhost:8080/api/tick

• 生成火焰图

yarn flame

• 效果
  可以看出calculateStringDistance 占用是比较高的
  

   

   

• 说明
  对于火焰图的生成使用了flamebearer 工具，实际上perf 也是一个很强大的工具，提供nodejs 官方也介绍了如何使用perf 进行分析

参考资料

https://nodejs.org/en/docs/guides/diagnostics-flamegraph/
https://github.com/mapbox/flamebearer
https://nodejs.org/uk/docs/guides/simple-profiling/