update(api): enable Google Edge caching.

Relates to #104

lib/controllers/api/index.js

@@ -15,6 +15,7 @@ var express = require('express'),
   CacherRedis = require('cacher-redis');
 
 module.exports = function (app) {
+  const EDGE_CACHE_MAX_AGE = 3600; // 1 hr
   var versions = [];
   var rateHandler;
   var cacher;
@@ -131,6 +132,19 @@ module.exports = function (app) {
     rm(req, res, next);
   };
 
+
+  /**
+   * Enable Google Edge caching for our API
+   * @param req
+   * @param res
+   * @param next
+   */
+  var edgeCache = function (req, res, next) {
+    res.header('Cache-Control', 'public, max-age=' + EDGE_CACHE_MAX_AGE);
+    res.header('Pragma', 'Public');
+    next();
+  };
+
   require('fs').readdirSync(__dirname + '/').forEach(function (file) {
     if (file.match(/.+\.js/g) === null) {
       var version = file;
@@ -142,6 +156,7 @@ module.exports = function (app) {
       impl.use(apiKeyMiddleware);
       impl.use(rateMiddleware);
       impl.use(analyticsMiddleware(version));
+      impl.use(edgeCache);
 
       impl.route = function (method, path, metadata) {
         var args = Array.prototype.slice.call(arguments);