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Tiny API with Nginx

How to build a tiny REST API using Nginx, Memcached and GeoIP.

tl;dr

As it turns out, Nginx can be configured to act like a full fledged REST API. No web application needed.

Background

We had the need for a tiny API and we figured that the problem was simple enough to be implemented inside of Nginx. The three requirements for the API was;

  1. Responses in JSON (and JSONP)
  2. Client country using GeoIP
  3. Data retrieved from Memcached

I recommend that you use the OpenResty (aka. ngx_openresty) bundle if you want to install Nginx, it contains a few really good third party modules. I’m using five Nginx modules in this project; Echo, GeoIP, Memc, RealIp and XSS.

The complete nginx.conf

worker_processes 4;
events {}

http {
  access_log    off;
  error_log     off;
  geoip_country /path/to/GeoIP.dat;

  server {
    listen            9999;
    real_ip_header    X-Real-IP;
    set_real_ip_from  127.0.0.1;

    location /redirect_ip {
      internal;
      set $memc_key 'redirect';
      memc_pass 127.0.0.1:11211;
    }

    location /loadbalancer.json {
      default_type "application/json";

      echo -n "{\"geoip_country_code\":\"$geoip_country_code\",";
      echo -n "\"redirect\":\"";
      echo_location -n /redirect_ip;
      echo -n "\"}";

      xss_get on;
      xss_callback_arg callback;
      xss_output_type 'application/x-javascript';
    }

    location /loadbalancer {
      if ($request_method != POST) { return 405; }

      allow 127.0.0.1;
      deny all;

      set $memc_key 'redirect';
      set $memc_cmd 'set';
      set $memc_value $arg_var;
      memc_pass 127.0.0.1:11211;
    }
  }
}

Using the API

I like to use cURL when manually testing API’s:

Updating the “redirect” value in Memcached via the API

curl -X POST http://0.0.0.0:9999/loadbalancer?var=10.0.0.5
#=> STORED

Retrieve the JSON

curl -H "X-Real-IP: 213.115.122.2" \
http://0.0.0.0:9999/loadbalancer.json
#=> {"geoip_country_code":"SE", "redirect":"10.0.0.5"}

And if we want to use JSONP:

curl -H "X-Real-IP: 213.115.122.2" \
http://0.0.0.0:9999/loadbalancer.json?callback=foo
#=> foo({"geoip_country_code":"SE", "redirect":"10.0.0.5"});