Add caching to routes

POST requests will set to cache, but never read from it
GET requests will set to, and read from, cache. If `no-cache` is present in the `cache-control` header, a fresh/non-cached version will be retrieved, set to cache, and returned

services/oembed/src/app.js

@@ -3,6 +3,7 @@ const helmet = require('helmet');
 const { json } = require('body-parser');
 const { asyncRoute } = require('@parameter1/base-cms-utils');
 const embedly = require('./embedly');
+const cache = require('./cache');
 
 const app = express();
 const dev = process.env.NODE_ENV === 'development';
@@ -12,15 +13,28 @@ app.use(json());
 app.set('trust proxy', ['loopback', 'linklocal', 'uniquelocal']);
 
 app.post('/', asyncRoute(async (req, res) => {
-  const { body } = req;
-  const data = await embedly.oembed(body.url, body.params);
+  const { url, ...params } = req.body;
+  const data = await embedly.oembed(url, params);
+  // post will set to cache, but not read from it
+  await cache.setFor({ url, params, data });
   res.json(data);
 }));
 
 app.get('/', asyncRoute(async (req, res) => {
-  const { query } = req;
-  const data = await embedly.oembed(query.url, query);
-  res.json(data);
+  const { url, ...params } = req.query;
+  const cacheControl = req.headers['cache-control'];
+  const noCache = cacheControl && /no-cache/i.test(cacheControl);
+
+  // allow for fresh data retrieval
+  const cached = noCache ? null : await cache.getFor({ url, params });
+  res.set('X-Cache', cached ? 'hit' : 'miss');
+  if (cached) {
+    res.set('Age', cached.age);
+    return res.json(cached.data);
+  }
+  const data = await embedly.oembed(url, params);
+  await cache.setFor({ url, params, data });
+  return res.json(data);
 }));
 
 // eslint-disable-next-line no-unused-vars

services/oembed/src/cache.js

@@ -0,0 +1,30 @@
+const { createHash } = require('crypto');
+const redis = require('./redis');
+
+const createCacheKey = ({ url, params } = {}) => {
+  const hash = createHash('sha256').update(JSON.stringify({ url, params })).digest('hex');
+  return `base_oembed:${hash}`;
+};
+
+const getFor = async ({ url, params } = {}) => {
+  const key = createCacheKey({ url, params });
+  const serialized = await redis.get(key);
+  if (!serialized) return null;
+  const cacheValue = JSON.parse(serialized);
+  const age = Math.round((Date.now() - cacheValue.cacheTime) / 1000);
+  return { ...cacheValue, age };
+};
+
+const setFor = async ({ url, params, data } = {}) => {
+  const key = createCacheKey({ url, params });
+  const cacheValue = { data, cacheTime: Date.now() };
+  const ttl = 60 * 60 * 24 * 3; // cache for 72 hours
+  await redis.set(key, JSON.stringify(cacheValue), 'EX', ttl);
+};
+
+
+module.exports = {
+  createCacheKey,
+  getFor,
+  setFor,
+};