init api rate-limit on geolocation api routes

server/api/controller/geolocation.js

@@ -0,0 +1,38 @@
+const rateLimit = require('express-rate-limit');
+const log = require('../../log')
+let curReq
+
+const geolocationController = {
+  rateLimiter: rateLimit({
+    windowMs: 15 * 60 * 1000, // 15 minutes
+    max: 100, // Limit each IP to 100 requests per `window` (here, per 15 minutes)
+    standardHeaders: true, // Return rate limit info in the `RateLimit-*` headers
+    legacyHeaders: false, // Disable the `X-RateLimit-*` headers
+  }),
+
+  /** 
+   * Limit api usage
+   * From https://operations.osmfoundation.org/policies/nominatim/
+   * [Requirements] No heavy uses (an absolute maximum of 1 request per second).
+   * [Websites and Apps] Note that the usage limits above apply per website/application: the sum of traffic by all your users should not exceed the limits.
+   */
+  apiLimit (req, res, next) {
+    prevReq = curReq
+    curReq = Date.now()
+    deltaTime = (curReq - prevReq)
+
+    if (typeof prevReq === 'undefined' || deltaTime > 1000) {
+      geolocationController.rateLimiter(req, res, next)
+    } else {
+      log.warn('More than 1 request per second to geolocation api come from ' + req.ip)
+
+      setTimeout(() => {
+        geolocationController.rateLimiter(req, res, next)
+      }, 1000 - deltaTime)
+    }
+    
+  }
+  
+}
+
+module.exports = geolocationController