Jozsef Suba jozsefs

Scaling your API with rate limiters

The following are examples of the four types rate limiters discussed in the accompanying blog post. In the examples below I've used pseudocode-like Ruby, so if you're unfamiliar with Ruby you should be able to easily translate this approach to other languages. Complete examples in Ruby are also provided later in this gist.

In most cases you'll want all these examples to be classes, but I've used simple functions here to keep the code samples brief.

Request rate limiter

This uses a basic token bucket algorithm and relies on the fact that Redis scripts execute atomically. No other operations can run between fetching the count and writing the new count.

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

So you're curious in learning this new thing called Reactive Programming, particularly its variant comprising of Rx, Bacon.js, RAC, and others.

Learning it is hard, even harder by the lack of good material. When I started, I tried looking for tutorials. I found only a handful of practical guides, but they just scratched the surface and never tackled the challenge of building the whole architecture around it. Library documentations often don't help when you're trying to understand some function. I mean, honestly, look at this:

Rx.Observable.prototype.flatMapLatest(selector, [thisArg])

Projects each element of an observable sequence into a new sequence of observable sequences by incorporating the element's index and then transforms an observable sequence of observable sequences into an observable sequence producing values only from the most recent observable sequence.

	const Queue = require('then-queue'); // async queue that doesn't care what order you call push and pop.

	const queue = new Queue();

	// push sends to the first waiting `pop` if available, otherwise it acts as a buffer
	listenToNewMessages(message => queue.push(message));

	async function* MessagesGenerator() {
	try {
	while (true) {

	html,
	body,
	#doc {
	height: 100%; // Passes through the height of the parent iframe element
	}
	#doc {
	// Magic to prevent iOS growing the iFrame to fit the content.
	// This container will mimic the behavior of the iframe on a desktop browser
	-webkit-overflow-scrolling:touch;
	overflow-y: scroll;

	function createUser(username, callback) {
	var connection = DatabaseClient.connect();
	var users = connection.call('collection', 'users');
	var query = users.call('query', {username: username});
	return query.then(function(existing){
	if(existing) throw new Error("User already exists: " + username);
	else return users.call('create', {username: username});
	}).fin(function(connection){ return connection.call('close'); });
	}