0 to 1 Million: Scaling my side project to 1 million requests a day

In the Beginning

In late 2014 I decided that I needed a side project.  There were some technologies that I wanted to learn, and in my experience building an actual project was the best way to do that.  As I sat on my couch trying to figure out what to build, I remembered an idea I had back when I was still a junior dev doing WordPress development.  The idea was that people building commercial plugins and themes should be able to use the automated update system that WordPress provides.  There were a few self-managed solutions out there for this, but I thought building a SaaS product would be a good way to learn some new tech.

Getting Started

My programming history in 2014 looked something like: LAMP (PHP, MySQL, Apache) -> Ruby on Rails -> Django.  In 2014 Node.js was becoming extremely popular and MongoDB had started to become mature.  Both of these technologies interested me, so I decided to use them on this new project.  As to not get too overwhelmed with learning things, I decided to use Angular for fronted since I was already familiar with it.

A few months after getting started, I finally deployed https://kernl.us for the world to see.  To give you an idea of the expectations I had for this project, I deployed it to a $5/month Digital Ocean droplet.  That means everything (Mongo, Nginx, Node) was on a single $5 machine.  For the next month or two, this sufficed since my traffic was very low.

The First Wave

In December of 2014 things started to get interesting with Kernl.  I had moved Kernl out of a closed alpha and into beta, which led to a rise in sign ups.  Traffic steadily started to climb, but not so high that it couldn’t be handled by a single $5 droplet.

Around December 5th I had a customer with a large install base start to use Kernl.  As you can see the graph scale completely changes.  Kernl went from ~2500 requests per day, to over 2000 requests per hour.  That seems like a lot (or it did at the time), but it was still well within what a single $5 droplet could handle.  After all, thats less that 1 request per second.

Scaling Up

Through the first 3 months of 2015 Kernl experienced steady growth.  I started charging for it in February, which helped fuel further growth as it made customers feel more comfortable trusting it with something as important as updates.  Starting in March, I noticed that resource consumption on my $5 droplet was getting a bit out of hand.  Wanting to keep costs low (both in my development time and actual money) I opted to scale Kernl vertically to a $20 per month droplet.  It had 2GB of RAM and 2 cores, which seemed like plenty.  I knew that this wasn’t a permanent solution, but it was the lowest friction one at the time.

During the ‘Scaling Up’ period that Kernl went through, I also ran into issues with Apache.  I started out by using Apache as a reverse proxy because I was familiar with it, but it started to fall over on me when I would occasionally receive requests rates of about 20/s.  Instead of tweaking Apache, I switched to using Nginx and have yet to run in to any issues with it.  I’m sure Apache can handle far more that 20 requests/s, but I simply don’t know enough about tweaking it’s settings to make that happen.

SCaling Out & Increasing Availability

For the rest of 2015 Kernl saw continued steady growth.  As Kernl grew and customers started to rely on it for more than just updates (Bitbucket / Github push-to-build), I knew that it was time to make things far more reliable and resilient than they currently were.  Over the course of 6 months, I made the following changes:

  • Moved file storage to AWS S3 – One thing that occasionally brought Kernl down or resulted in dropped connections was when a large customer would push an update out.  Lots of connections would stay open while the files were being download, which made it hard for other requests to get through without timing out.  Moving uploaded files to S3 was a no-brainer, as it makes scaling file downloads stupid-simple.
  • Moved Mongo to Compose.io – One thing I learned about Mongo was that managing a cluster is a huge pain in the ass.  I tried to run my own Mongo cluster for a month, but it was just too much work to do correctly.  In the end, paying Compose.io $18/month was the best choice.  They’re also awesome at what they do and I highly recommend them.
  • Moved Nginx to it’s own server – In the very beginning, Nginx lived on the same box as the Node application.  For better scaling (and separation of concerns) I moved Nginx to it’s own $5 droplet.  Eventually I would end up with 2 Nginx servers when I implemented a floating ip address.
  • Added more Node servers – With Nginx living on it’s own server, Mongo living on Compose.io, and files being served off of S3, I was able to finally scale out the Node side of things.  Kernl currently has 3 Node app servers, which handle requests rates of up to 170/second.

Final Thoughts

Over the past year I’ve wondered if taking the time to build things right the first time through would have been worth it.  I’ve come to the conclusion that optimizing for simplicity is probably what kept me interested in Kernl long enough to make it profitable.  I deal with enough complication in my day job, so having to deal with it in a “fun” side project feels like a great way to kill passion.

What’s New With Kernl – November 2016

It’s been a long time since the last Kernl update blog, so lets get right into it.

Big Features

  • GitLab CI Support – You can now build your plugins and themes automatically on Kernl using GitLab.com!  We’ve had support for GitHub and BitBucket for a long time, and finally figured out a good way to make things work for GitLab.  See the documentation on how to get started.
  • Slack Build Integration – If you are a slack user, you can now tell Kernl where to publish build status messages.
  • Replay Last Webhook – Sometimes when you’re running a CI service with Kernl it would be useful to re-try that last push that Kernl received.  You can now do that on the “Continuous Integration” page.

Minor Features

  • Repository Caching – We now do some minor caching of your git repositories on the Kernl front end.  The first load will still reach out to the different git providers, but subsequent loads during your sessions will read an in-memory cache instead.
  • Better Webhook Log Links – Instead of displaying a UUID, the webhook build log now displays the name of the plugin or theme.

Other

  • Miscellaneous Upgrades – Underlying OS packages and Node.js packages were upgraded.
  • Payment Bug Fixes – There were a few minor bugs that kept showing up if someone’s credit card expired.  This fix hopefully allows for a more self-service approach.
  • Minor copy changes – A few changes were made to the wording on the Kernl landing page.

What’s next?

  • It’s been a few months since Ubuntu 16.04 LTS came out, so I’ll be spending significant amounts of time upgrading our infrastructure to the latest LTS version.
  • If our load balancer goes down right now, everything goes under.  A floating IP address between two load balancers will solve that issue and provide high(er) availability.
  • Better insights into purchase code usage and activity.

Two Frameworks

The past couple of months have found me working diligently on work stuff, but also consistently dropping an hour a day on my current side project.  It just so happens that the side project and my actual work share the same language (Python) and framework (Django).  This has been nice because it’s given my brain a moment to relax with regards to learning new material,  but at the same time I feel stagnate.

Django is my framework of choice.   I know it inside and out, can bend it to my will, and work extremely fast in it.  However I’m not blind to the fact that the popularity of the old monolithic frameworks(Rails, Django, Cake, etc) for new projects is waning.  People these days are starting new projects with a service oriented architecture in mind.  They’re using Node.js with Express on the backend for an API, and then Angular on the front end to create a nice single page app.  I’ve done this sort of development before extensively, but I’m out of practice.  So I’ve come to a fork in the road.

Over the years I’ve come to realize that I can only hold two frameworks in my mind at one time. It doesn’t matter if they are written in different languages or not (those seem to stick with me easier for some reason), but two frameworks is the max I can handle.  So my choices are as follows:  1) Learn Android, 2) Get good at Node.

I’ve made one Android app before when I worked at a marketing firm.  It was fun.  I enjoyed not doing web stuff for once.  I found Java overly verbose,  but as long as you stayed within the “modern Java” lines it was fine.  As for Node, I already know it but I’m just out of practice.  I feel like it would be valuable to become an expert in but sometimes I feel burnt out on the web.

After a lot of deliberation, I think I’m going to move forward with Android development by making an Android app for RedemFit.  It’ll give me a chance to break out of Web development for awhile and hopefully will become something I enjoy doing as much as web.

Using Restangular with Django TastyPie

TastyPie’s JSON responses split the response into two sections: meta data and actual data. The meta is really nice, because it helps you data pagination, result counts, and the like, but it kind of gets in the way of Restangular. Integrating with Restangular is easy though!

Add the following to your app.js file.

yourApp.config(function(RestangularProvider) {
    RestangularProvider.setBaseUrl("/api");
    RestangularProvider.setResponseExtractor(function(response, operation, what, url) {
        var newResponse;
        if (operation === "getList") {
            newResponse = response.objects;
            newResponse.metadata = response.meta;
        } else {
            newResponse = response;
        }
        return newResponse;
    });
    RestangularProvider.setRequestSuffix('/?');
});

Done.

Creating jQuery Plugins

Update: I was able to get permission to release the iScroll plugin! Check it out here.

Not too long ago I decided to write a jQuery plugin for making the use of iScroll a little less painful. Since I made the plugin at work I’m not really at liberty to share it. But what I can share is a step by step tutorial for creating a jQuery plugin of your own. Let’s get started.

Step 1: Scope

If you’ve been writing Javascript with jQuery for any amount of time, you find out pretty quickly that proper scoping is very important. You also learn that the $ symbol isn’t reliable. So what’s a coder to do? Make sure that your scope is contained within an anonymous function, and that you pass the jQuery object into that function.

(function($) {
	console.log($(document).jquery);
})(jQuery);

If you paste this code into your console (assuming jQuery is included), you should receive a print out of what version of jQuery you’re using.

Step 2: Functions

Now that you have the basic wrapper written, we need to write some real code. Before we start, there are 3 things you need to know.

  1. Functions are attached to the $.fn object.
  2. There may be more than one element passed into your function (plugin)
  3. We want to keep the chain alive if possible. (See jQuery Chaining if you have questions)

So, let’s write a function that adds the class “bob” to every item in the set. Yes, we could just use the .addClass() method, but then we wouldn’t need to write a plugin would we?

(function($) {
	$.fn.addBob = function() {  //Add the function
		return this.each(function() { //Loop over each element in the set and return them to keep the chain alive.
			var $this = $(this);
			$this.addClass("bob");
		});
	};
})(jQuery);

Step 3: Options

So let’s say you need to pass some options to your plugin. You know, like Bob’s last name, or if we should remove Bob. To accomplish this, all you do is create a defaultOptions object and load it with defaults. Then you use the $.extend function to overwrite it’s values with values passed in as a function parameter.

(function($) {
	$.fn.addBob = function(customOptions) {  //Add the function
		var options = $.extend({}, $.fn.addBob.defaultOptions, customOptions);
		return this.each(function() { //Loop over each element in the set and return them to keep the chain alive.
			var $this = $(this);
 
			//Determine what name to use.
			var name = "";
			if(options.lastName != "") {
				name = "bob-" + options.lastName;
			} else {
				name = "bob";
			}
 
			//Are we removing items?
			if(options.remove) {
				$this.removeClass(name);
			} else {
				$this.addClass(name);
			}
		});
	};
 
	$.fn.addBob.defaultOptions = {
		lastName : "",
		remove : false	
	};
})(jQuery);

Step 4: Running your plugin

Now that you’ve written your plugin, you need to run it!
Before

<ol id='x'>
	<li></li>
	<li></li>
</ol>
<ol id='y'>
	<li></li>
	<li></li>
</ol>

JS

	$("#x li, #y li").addBob({lastName: "awesome"});

After

<ol id='x'>
	<li class='bob-awesome'></li>
	<li class='bob-awesome'></li>
</ol>
<ol id='y'>
	<li class='bob-awesome'></li>
	<li class='bob-awesome'></li>
</ol>

JS

	$("#y li").addBob({lastName: "awesome", remove: true});

After

<ol id='x'>
	<li class='bob-awesome'></li>
	<li class='bob-awesome'></li>
</ol>
<ol id='y'>
	<li></li>
	<li></li>
</ol>

That’s all there is to it. If you have any questions, leave a comment and I’ll get back to you as soon as I can.

jQuery Chaining

jQuery is the jewel in the crown that is web development. Once you discover it, Javascript is no longer a chore to write, hell, it might even be considered fun! Sure being able to select elements by ID, class, or type is great, but what about all the other stuff? What about chaining? I’ve heard such great stuff about it!

Chaining

The first thing you need to know about chaining is that you chain actions on to collections. A collection is what is returned when you select something using jQuery.

$("input");  //Collection of all input elements on the page.

When most people start using jQuery, they do something like this:

$("input").val("123");
$("input").addClass("awesome");
$("input").attr("data-bind", "15");

Yes, this code will work, but it’s inefficient. Every time you perform a selection, jQuery must traverse the DOM and find all the input elements. If you use chaining, it will simply use the collection of input elements that it already has.

$("input")
	.val("123")
	.addClass("awesome")
	.attr("data-bind", "15");

So why does this work? Because each method that you call in the chain returns the collection. So in this case “val()”, “addClass()”, and “attr()” all return “$(input)”. However, not all methods support chaining. For instance, the “text()” method breaks the chain, so if you’re going to use it, do it at the end.
What if you want to keep the chain alive though? No problem. You can simply back-out of the destructive action using the “end()” method.

Before

<ol id='mylist'>
	<li>
	</li>
	<li>
	</li>
	<li>
	</li>
</ol>

Javascript

$('#mylist')
	.find('>li')
		.filter(':last')
			.addClass('Meow')
		.end()
		.filter(':first')
			.addClass('Mix')
		.end()
		.addClass('catfood')
	.end()
	.addClass('thelist');

After

<ol id='mylist' class='thelist'>
	<li class='Mix catfood'>
	</li>
	<li class='catfood'>
	</li>
	<li class='Meow catfood'>
	</li>
</ol>

While sometimes confusing, you can see that chaining is often the most efficient way to handle modifying the DOM.

Writing Chainable Plugins/Functions

Now that you know all about chaining, you’ll probably want to write your own chainable plugins/functions. It’s very easy to do this, since all you need to do is return the jQuery object at the end of the function.

In this example, we’ll write a plugin that attaches a second counter to an element.

Plugin

(function($) {
	$.fn.count = function() {
		return this.each(function() {  //We do an 'each', because the collection may have more than one item in it.
			var self = $(this);  //
			self.html('0');
			var theInterval = window.setInterval(function() {
				var c = parseFloat(self.text());
				self.html(c + 1);
			}, 1000);
		});
	}
}) (jQuery);

HTML

<div>
	<span id='test'></span>
</div>

Execution

$("#test").count().parent().addClass('counters'); //Chaining still works :)