Tech Tips

概要

node.jsでアプリを作成しているとメモリリーク（やCPUの負荷）に悩まされることが多い。
多くはスナップショットを撮ってボトルネックを見つけて改善することできたから、
ここではその方法を載せる。
スナップショットの結果はライブラリの関係上Chromeブラウザの開発者ツールで確認する。

環境

• OS
  • Linux www4322gi 3.2.0-64-generic #97-Ubuntu SMP Wed Jun 4 22:04:21 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
• Node
  • version: v0.10.26
• Library
  • nodegrind
  • heapdump

事前準備

ここからnvmとnode.jsをインストールする。

構築

expressのテンプレート作成

$ vim package.json
{
  "name": "snapshot_test",
  "version": "0.0.1",
  "dependencies": {
    "express": "4.8.7",
    "ejs": "1.0.0",
    "express-generator": "4.8.0"
  }
}

$ npm install

$ ls node_modules/.bin/
express

$ ./node_modules/.bin/express -e -t ejs snapshot_test

$ ls snapshot_test/
app.js  bin  package.json  public  routes  views

サンプルアプリ開発

$ cd snapshot_test
$ vim package.json
{
  "name": "snapshot_test",
  "version": "0.0.0",
  "private": true,
  "scripts": {
    "start": "node ./bin/www"
  },
  "dependencies": {
    "express": "~4.8.6",
    "body-parser": "~1.6.6",
    "cookie-parser": "~1.3.2",
    "morgan": "~1.2.3",
    "serve-favicon": "~2.0.1",
    "debug": "~1.0.4",
    "ejs": "~0.8.5",
    "request": "2.40.0",
    "cheerio": "0.17.0"
  }
}

$ npm update

routes/index.js

var express = require('express');
var router = express.Router();

var request = require('request');
var cheerio = require('cheerio');

/* GET home page. */
router.get('/', function(req, res) {
  var url = 'http://160.16.71.152:12080/';

  request(url, function (error, response, body) {
    // Connection success
    if (!error && response.statusCode == 200) {
      // Parse
      var $ = cheerio.load(body);
      var hrefs = [];

      // Retrieve all link urls in the page
      $('a').each(function() {
        hrefs.push($(this).attr('href'));
      });

      // return response
      var result = {}
      result.status = 'success';
      result.contents = hrefs;
      res.send(JSON.stringify(result));
    // Error result
    } else {
      var result = {}
      result.status = 'error';
      result.contents = '';
      res.send(JSON.stringify(result));
    }
  })
});

module.exports = router;

スナップショット部分の開発

$ vim package.json
{
  "name": "snapshot_test",
  "version": "0.0.0",
  "private": true,
  "scripts": {
    "start": "node ./bin/www"
  },
  "dependencies": {
    "express": "~4.8.6",
    "body-parser": "~1.6.6",
    "cookie-parser": "~1.3.2",
    "morgan": "~1.2.3",
    "serve-favicon": "~2.0.1",
    "debug": "~1.0.4",
    "ejs": "~0.8.5",
    "request": "2.40.0",
    "cheerio": "0.17.0",
    "nodegrind": "0.1.8",
    "heapdump": "0.2.10"
  }
}

$ npm update

routes/snapcpu.js

var express = require('express');
var router = express.Router();

var fs = require('fs');
var profiler = require('nodegrind');

router.get('/', function(req, res) {
  // filename
  var name =  (new Date().getTime()) + '.cpuprofile';

  // Start to measure
  profiler.startCPU(name);

  // Stop to measure after 5 sec
  setTimeout(function(){
    var cpuProfile = profiler.stopCPU(name, 'cpuprofile');

    //Write profile
    fs.writeFile(name, cpuProfile, function(err){
      if (err) res.send(err);
      else     res.send('OK:' + name);
    });
  }, 5000);
});

module.exports = router;

routes/snapheap.js

var express = require('express');
var router = express.Router();

var fs = require('fs');
var heapdump = require('heapdump');

router.get('/', function(req, res) {
  // filename
  var name = (new Date().getTime()) + '.heapsnapshot';

  // Take a snapshot of heap
  heapdump.writeSnapshot(name, function() {
    res.send('OK:' + name);
  });
});

module.exports = router;

ルーティングの設定

app.js

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');

var routes = require('./routes/index');
var users = require('./routes/users');
var snapcpu = require('./routes/snapcpu');
var snapheap = require('./routes/snapheap');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');

// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', routes);
app.use('/users', users);
app.use('/snapcpu', snapcpu);
app.use('/snapheap', snapheap);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
    var err = new Error('Not Found');
    err.status = 404;
    next(err);
});

// error handlers

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
    app.use(function(err, req, res, next) {
        res.status(err.status || 500);
        res.render('error', {
            message: err.message,
            error: err
        });
    });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
        message: err.message,
        error: {}
    });
});

module.exports = app;

動作確認

$ curl http://127.0.0.1:3000
{"status":"success","contents":["http://160.16.71.152:12080/","http://160.16.71.152:12080/?page_id=382",.....................,"http://www.adazing.com/"]}

スナップショット確認

ヒープのスナップショット

$ for i in `seq 5`; do curl 'http://127.0.0.1:3000/'; sleep 1s; done

$ curl http://127.0.0.1:3000/snapheap
OK:1409475822884.heapsnapshot

$ ls
1409475822884.heapsnapshot  app.js  bin  node_modules  package.json  public  routes  views

CPU使用率のスナップショット

$ for i in `seq 10`; do curl 'http://127.0.0.1:3000'; sleep 1s; done

# Do following command during for loop
$ curl http://127.0.0.1:3000/snapcpu

$ ls
1409475822884.heapsnapshot  1409477190566.cpuprofile  app.js  bin  node_modules  package.json  public  routes  views

Chromeブラウザで結果を確認

CPUとヒープ