how to profile nodejs applications

v8profiler.js

var fs = require('fs');
var profiler = require('@risingstack/v8-profiler')
var request = require('request')
var samplingIntervalMicros = 1000;
var express = require('express')
var app = express();
var bodyParser = require('body-parser')

var enableProfiler = false;

app.use(bodyParser.json())
app.use(bodyParser.urlencoded({
    extended: false
}))

app.get('/', function (req, res) {

    var startTime = new Date();

    if(req.query.enable == 'true'){
        enableProfiler = true;
    }else{
        enableProfiler = false;
    }

    if (enableProfiler) profiler.startProfiling('1', true);

    request.get('https://nodejs.org/api/fs.html', function (err, data) {

        if (err) throw err;

        
        fs.stat('./package.json', function (err, stats) {
            if (err) throw err;

            fs.readFile(__filename, function readFileCallback(err, data) {
                if (err) throw err;

                setTimeout(function timeoutCallback() {
                    if (enableProfiler) {

                        var profile1 = profiler.stopProfiling();

                        fs.writeFileSync('./profile1.json', JSON.stringify(profile1));

                        var profileWithTimingInformation = exports.toTreeWithTiming(profile1, samplingIntervalMicros);
                        console.log('v8 profiler completed.......')
                        fs.writeFileSync('./profile1_modified.json', JSON.stringify(profileWithTimingInformation));

                    }

                    console.log('execution time :', new Date() - startTime)
                    res.send('success!!!!!!!!!')
                    // console.log('profile header', profile1.getHeader());

                    // profile1.export(function (error, result) {

                    //     var profile = profiler.stopProfiling();


                    //     fs.writeFileSync('profile1.json', result);
                    //     profile1.delete();

                    //     res.send('success!!!!!!!!!')
                    // });

                }, 9000)
            })
        })
    })


})


exports.toTreeWithTiming = function toTreeWithTiming(profile) {
    return processRawNode(profile.head);
};


function processRawNode(rawNode) {

    /**
     S= self time & total time
     self is how much time was spent doing work directly in that function.

       total is how much time was spent in that function, and in the functions it called.
     */
     
    //How to  calculate self time or method time and total time in V8 Profiler 
    //https://github.com/jlfwong/chrome2calltree
    /**
        
        "functionName": "(root)",
        "url": "",
        "lineNumber": 0,
        "callUID": 108,
        "bailoutReason": "",
        "id": 1,
        "scriptId": 0,
        "hitCount": 2,

        (%N = Name and line no. & Method name, %M = method time, %T = total time, %c = Class Name, %m = Method name
     */
    var node = {
        functionName: rawNode.functionName,
        url: rawNode.url,
        lineNumber: rawNode.lineNumber,
        sh: rawNode.hitCount,
        th: rawNode.hitCount,
        selfTime: 0,
        totalTime: 0,
        b: getBailoutReason(rawNode),
        children: []
    };

    var children = rawNode.children;
    for (var i = 0, len = children.length; i < len; i++) {
        var childNode = processRawNode(children[i], samplingIntervalMicros);
        node.children.push(childNode);
        node.th += childNode.th;
    }

    node.totalTime = node.th * samplingIntervalMicros;
    node.selfTime = node.sh * samplingIntervalMicros;

    return node;
}


function getBailoutReason(rawNode) {
    var reason = rawNode.bailoutReason;
    if (!reason || reason === 'no reason') {
        return undefined;
    }
    return reason;
}

app.listen(8080, function () {
    console.log('app is listening in 8080 port')
})