cache-expire

measurement_viewer.py

 import sys
+from datetime import timedelta, datetime
 
 import tornado.ioloop
 import tornado.web
@@ -14,6 +15,12 @@ class MainHandler(tornado.web.RequestHandler):
         pollutions = yield models.Type.get_all()
         last_measurements = yield models.Measurement.get_all_last()
 
+        expire = datetime.today() + timedelta(hours=1)
+        expire -= timedelta(seconds=expire.second, minutes=expire.minute)
+        expire += timedelta(seconds=90)
+
+        self.add_header("Expires", expire)
+
         self.set_header('Content-Type', 'application/json')
         self.write(json.dumps(self.get_full_json_response(stations=stations, pollutions=pollutions,
                                                           last_measurements=last_measurements)))