Raul Ochoa rochoa

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.

modified version of http://bl.ocks.org/curran/01aa2685f083b6c1b9fb with the map's bounding box on the globe

original readme follows:

--

Pan and zoom in the map on the left to rotate the globe.

Click and drag the globe to pan on the map.

	CREATE OR REPLACE FUNCTION tile (z integer, x integer, y integer, query text) RETURNS TABLE(id int8, geom geometry)
	AS $$
	DECLARE
	sql TEXT;
	BEGIN
	sql := 'with _conf as (
	select
	CDB_XYZ_resolution(' \|\| z \|\| ') as res,
	1.0/CDB_XYZ_resolution(' \|\| z \|\| ') as invres,
	st_xmin(CDB_XYZ_Extent(' \|\| x \|\| ',' \|\| y \|\| ',' \|\| z \|\|')) as tile_x,

	-- Source code from https://github.com/CartoDB/crankshaft/blob/develop/src/pg/sql/30_dot_density.sql
	CREATE OR REPLACE FUNCTION cdb_dot_density(geom geometry , no_points Integer, max_iter_per_point Integer DEFAULT 1000)
	RETURNS GEOMETRY AS $$
	DECLARE
	extent GEOMETRY;
	test_point Geometry;
	width NUMERIC;
	height NUMERIC;
	x0 NUMERIC;
	y0 NUMERIC;

	CREATE OR REPLACE FUNCTION public.CDB_Delayed_TableMetadata_Trigger()
	RETURNS trigger AS $$
	DECLARE upd timestamp;
	BEGIN
	IF TG_RELID = 'cartodb.CDB_TableMetadata'::regclass::oid THEN
	RETURN NULL;
	END IF;
	SELECT updated_at INTO upd
	FROM cartodb.CDB_TableMetadata WHERE tabname = TG_RELID::regclass;
	IF upd IS NOT NULL AND (now() - upd) > '20m'::interval THEN

	WITH deltas as (
	SELECT
	st_distance(the_geom::geography, lag(the_geom::geography, 1) over(order by timestamp)) as ddist,
	timestamp - lag(timestamp, 1) over(order by timestamp) as dt
	from out_2 offset 1000
	)

	select avg(ddist/dt) as speed from deltas

	<!DOCTYPE html>
	<html>
	<head>
	<title>CartoDB + Leaflet interactivity example \| CartoDB.js</title>
	<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
	<meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
	<link rel="shortcut icon" href="http://cartodb.com/assets/favicon.ico" />
	<style>
	html, body, #map {
	height: 100%;