node package manager


A simple javascript profiler designed to work with node and express, especially helpful with cloud solutions like heroku.


A simple javascript profiler designed to work with node and express, especially helpful with cloud solutions like heroku.

In node + express environment, it simply tracks the start and end times of an express request, allowing additional triggers to be added in between. All triggers, start, and end times are logged when response is sent.

Where this shines is in the processing of these logs. By reading all logs generated over many hours or days (and from multiple sources), times can be summed up and total time spent between triggers can be known. This is useful when trying to ballpark where most of node app time is spent.

For example, if 2 triggers were added, one before and one after a chunk of code, the total time spent in that chunk of code can be known. And more importantly, that time as percent of the total time is known, so it is possible to know how much time is actually being spent by a chunk of code before it is optimized.


For example code, look at test/profile_time.test.js.

Run npm test to generate sample test/test.server.log based on the the above example code. You might need to run npm install --dev for tests.

Example node log looks like this:

% cat test/test.server.log
Server started up on port 3000
Server received request: /wait/420
2013-03-26T22:42:02.676Z profile_time /wait/420 {"b:ALL":0,"b:wait":0,"e:wait":420,"e:ALL":421}
Server received request: /wait/180
2013-03-26T22:42:03.100Z profile_time /wait/180 {"b:ALL":0,"b:wait":0,"e:wait":179,"e:ALL":180}

And analysis by bin/parse_logs.js reveals something like this:

% bin/parse_logs.js test/test.server.log
{ first: '2013-03-26T22:42:02.676Z',
  last: '2013-03-26T22:42:03.100Z',
  totalParsedLines: 2,
  totalLines: { wait: 2, ALL: 2 },
  totalTime: { wait: 599, ALL: 601 },
  averageTime: { wait: 300, ALL: 301 },
  percentTime: { wait: 99.7, ALL: 100 },
  percentLines: { wait: 100, ALL: 100 } }

Usage with node + express

profile_time was created to work easily within the express framework, part of node.js.

First, install

npm install profile_time

Second, add setup code

var profile_time = require('profile_time');
var express  = require('express');
var app = express();
app.use(; // will create req.profile_time

Lastly, insert req.profile_time.add() in your routes, like this

app.get('/category/:catg', function(req,res){
	req.profile_time && req.profile_time.add('category.jade');
	res.render('category.jade', data);

Usage with heroku + papertrail

Included is an example script to analyze log files, called parse_logs.js Feel free to copy and modify it for your needs. Basically you'll need to match the strings used in your req.profile_time.add(string).


parse_logs.js logfile.txt
heroku logs -n 1500  | ./parse_logs.js

Note that sometimes heroku logs inserts a newline char in the middle of a log line, which can prevent correct parsing. These occasional data points get skipped.

I personally use it with heroku and the papertrail addon, to scan all log lines from the previous day. With papertrail, you can get the last 7 days of archived log files, for free (10MB max per day).

% gzip -dc ~/download/2013-03-24.gz | ./bin/parse_logs.js 
{ first: '2013-03-24T00:00:00.375Z',
  last: '2013-03-24T23:59:58.836Z',
  totalParsedLines: 29046,
   { ALL: 29046,
     'category.jade': 14054,
     'product.jade': 7073,
     'product/detail.jade': 78 },
   { ALL: 17454705,
     'category.jade': 6816973,
     'product.jade': 3346311,
     'product/detail.jade': 2045 },
   { ALL: 601,
     'category.jade': 485,
     'product.jade': 473,
     'product/detail.jade': 26 },
   { ALL: 100,
     'category.jade': 39.1,
     'product.jade': 19.2,
     'product/detail.jade': 0 },
   { ALL: 100,
     'category.jade': 48.4,
     'product.jade': 24.4,
     'product/detail.jade': 0.3 } }

Usage in a browser

This could be used in a browser but sending times to something like stathat is much more effective. Requires free stathat account.

var startMs = new Date().getTime();
// long code here
var elapsedMs = new Date().getTime() - startMs;
$.ajax({url: ''+elapsMs});

Other profilers

If using heroku, newrelic is also one of my favorites. Definitely try them out for profiling and monitoring.

A list of several node profilers.