add caching based on lat/lon with a configurable timeout

README.md

@@ -17,3 +17,9 @@ When the API answers the request made by the proxy, the proxy resends the API re
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+
+## Caching
+
+To increase performance and prevent unnecessary duplicate calls to the Dark Sky APIs, the proxy allows caching with a timeout. When the timeout (in seconds) is reached for a particular lat/lon, updated data will be retrieved from Dark Sky.
+
+To enable this feature, specify a CACHE_TIMEOUT > 0 seconds.

endpoints/forecast.js

@@ -3,11 +3,20 @@ const request = require("request-promise");
 const { API_KEY } = process.env;
 const API_URL = `https://api.darksky.net/forecast/${API_KEY}`;
 
+const cache = {};
+
 let { CORS_WHITELIST } = process.env;
 if (CORS_WHITELIST) {
   CORS_WHITELIST = CORS_WHITELIST.replace(/ /g, "").split(",");
 }
 
+let { CACHE_TIMEOUT } = process.env;
+if (!CACHE_TIMEOUT) {
+  CACHE_TIMEOUT = 0;
+} else {
+  CACHE_TIMEOUT = parseInt(CACHE_TIMEOUT, 10);
+}
+
 const getResponseHeaders = request => {
   const headers = {
     "content-type": "application/json"
@@ -27,6 +36,23 @@ exports.handler = (event, context, callback) => {
     return;
   }
 
+  const now = Math.round(new Date().getTime() / 1000);
+
+  if (CACHE_TIMEOUT > 0) {
+    // see if we already have in the cache and the cache is < 1 hour old
+    const cachedItem = cache[`${lat},${lon}`];
+    if (!!cachedItem && now - cachedItem.time < CACHE_TIMEOUT) {
+      // console.log(`returning cached weather data for ${lat},${lon}`);
+      callback(null, {
+        body: JSON.stringify(cachedItem.response),
+        statusCode: 200,
+        headers: getResponseHeaders(event)
+      });
+      return;
+    }
+  }
+  // console.log(`fetching latest weather data for ${lat},${lon}`);
+
   const url = `${API_URL}/${lat},${lon}`;
   // Remove lat and lon parameters, they go in the URL
   delete qs.lat;
@@ -38,6 +64,12 @@ exports.handler = (event, context, callback) => {
   };
   request(url, options)
     .then(response => {
+      // cache response
+      cache[`${lat},${lon}`] = {
+        time: now,
+        response: response
+      };
+
       callback(null, {
         body: JSON.stringify(response),
         statusCode: 200,

netlify.toml

@@ -4,3 +4,4 @@
 [template.environment]
   API_KEY="Set your API key"
   CORS_WHITELIST="Optional comma-separated list of allowed cross-origin domains"
+  CACHE_TIMEOUT=3600