Implemented retrieval of alerts history

Tools/GardeningServer/alerts.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import calendar
 import datetime
 import json
 import logging
 import webapp2
 import zlib
 
 from google.appengine.api import memcache
+from google.appengine.api import users
+from google.appengine.datastore import datastore_query
 from google.appengine.ext import ndb
 
 LOGGER = logging.getLogger(__name__)
 
 
 class DateTimeEncoder(json.JSONEncoder):
     def default(self, obj):
         if isinstance(obj, datetime.datetime):
             return calendar.timegm(obj.timetuple())
         # Let the base class default method raise the TypeError.
         return json.JSONEncoder.default(self, obj)
 
 
 class AlertsJSON(ndb.Model):
+    key = ndb.StringProperty()

[Z_DONOTUSE, 2014/10/08 01:08:42]

key implies uniqueness to me. How about calling this field type?

[Sergiy Byelozyorov, 2014/10/08 12:50:26]

Done.

     json = ndb.BlobProperty(compressed=True)
     date = ndb.DateTimeProperty(auto_now_add=True)
 
 
 class AlertsHandler(webapp2.RequestHandler):
-    MEMCACHE_ALERTS_KEY = 'alerts'
+    ALERTS_KEY = 'alerts'
 
     # Has no 'response' member.
     # pylint: disable=E1101
     def send_json_headers(self):
         self.response.headers.add_header('Access-Control-Allow-Origin', '*')
         self.response.headers['Content-Type'] = 'application/json'
 
     # Has no 'response' member.
     # pylint: disable=E1101
     def send_json_data(self, data):
         self.send_json_headers()
         self.response.write(data)
 
     def generate_json_dump(self, alerts):
         return json.dumps(alerts, cls=DateTimeEncoder, indent=1)
 
     def get_from_memcache(self, memcache_key):
         compressed = memcache.get(memcache_key)
         if not compressed:
             self.send_json_headers()
             return
         uncompressed = zlib.decompress(compressed)
         self.send_json_data(uncompressed)
 
     def get(self):
-        self.get_from_memcache(AlertsHandler.MEMCACHE_ALERTS_KEY)
+        self.get_from_memcache(AlertsHandler.ALERTS_KEY)
 
-    def save_alerts_to_history(self, alerts):
+    def post_to_history(self, alerts_key, alerts):
         last_entry = AlertsJSON.query().order(-AlertsJSON.date).get()
         last_alerts = json.loads(last_entry.json) if last_entry else {}
 
         # Only changes to the fields with 'alerts' in the name should cause a
         # new history entry to be saved.
         def alert_fields(alerts_json):
             filtered_json = {}
             for key, value in alerts_json.iteritems():
                 if 'alerts' in key:
                     filtered_json[key] = value
             return filtered_json
 
         if alert_fields(last_alerts) != alert_fields(alerts):
-            new_entry = AlertsJSON(json=self.generate_json_dump(alerts))
+            new_entry = AlertsJSON(
+                json=self.generate_json_dump(alerts),
+                key=alerts_key)
             new_entry.put()
 
     # Has no 'response' member.
     # pylint: disable=E1101
     def post_to_memcache(self, memcache_key, alerts):
         uncompressed = self.generate_json_dump(alerts)
         compression_level = 1
         compressed = zlib.compress(uncompressed, compression_level)
         memcache.set(memcache_key, compressed)
 
     def parse_alerts(self, alerts_json):
         try:
             alerts = json.loads(alerts_json)
         except ValueError:
             warning = 'content field was not JSON'
             self.response.set_status(400, warning)
             LOGGER.warn(warning)
             return
 
         alerts.update({'date': datetime.datetime.utcnow()})
 
         return alerts
 
-    def update_alerts(self, memcache_key):
+    def update_alerts(self, alerts_key):
         alerts = self.parse_alerts(self.request.get('content'))
         if alerts:
-            self.post_to_memcache(memcache_key, alerts)
-            self.save_alerts_to_history(alerts)
+            self.post_to_memcache(alerts_key, alerts)
+            self.post_to_history(alerts_key, alerts)
 
     def post(self):
-        self.update_alerts(AlertsHandler.MEMCACHE_ALERTS_KEY)
+        self.update_alerts(AlertsHandler.ALERTS_KEY)
+
+
+class AlertsHistory(webapp2.RequestHandler):
+    MAX_LIMIT_PER_PAGE = 100
+
+    def get(self):
+        alerts_query = AlertsJSON.query().order(-AlertsJSON.date)
+
+        # Return only public alerts for non-internal users.
+        user = users.get_current_user()
+        if not user or not user.email().endswith('@google.com'):
+            alerts_query = alerts_query.filter(
+                AlertsJSON.key == AlertsHandler.ALERTS_KEY)
+
+        cursor = self.request.get('cursor')
+        if cursor:
+            cursor = datastore_query.Cursor(urlsafe=cursor)
+
+        limit = int(self.request.get('limit', self.MAX_LIMIT_PER_PAGE))
+        limit = min(self.MAX_LIMIT_PER_PAGE, limit)
+
+        if cursor:
+            alerts, next_cursor, has_more = alerts_query.fetch_page(
+                limit, start_cursor=cursor)
+        else:
+            alerts, next_cursor, has_more = alerts_query.fetch_page(limit)
+
+        combined_json = {
+            'has_more': has_more,
+            'cursor': next_cursor.urlsafe() if next_cursor else '',
+            'history': [json.loads(alert.json) for alert in alerts]
+        }
+
+        self.response.headers['Content-Type'] = 'application/json'
+        self.response.out.write(json.dumps(combined_json))
 
 
 app = webapp2.WSGIApplication([
-    ('/alerts', AlertsHandler)
+    ('/alerts', AlertsHandler),
+    ('/alerts-history', AlertsHistory)
 ])