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main.py
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main.py
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#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
import logging
import os
from google.appengine.ext import ndb
import jinja2
import webapp2
from models import MovieQuote
# Jinja Environment instance necessary to use Jinja templates.
jinja_env = jinja2.Environment(
loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
autoescape=True)
# Strong Consistency
# Lock thing down until everything is done
# Generic key to serve as the parent
# When a Datastore entity is "put" into the Datastore really what happens is an event is created to do the "put" eventually,
# but flow is returned for speed reasons immediately (the real "put" is slow and done later on another thread).
# Then the page was reloading before the "put" actually finished and new quotes weren't displayed.
# We added a parent key to all MovieQuote entities, then did an Ancesotr Query for entities that had that parent key.
# Ancestor Queries will look for unfinished events within the entity group and wait for them to complete before running the query.
# The potential problem with this solution is that If you had a million users you wouldn't want to lock down the entire Datastore using
# a single shared parent for all users. If you were worried about scaling to milllions of people there needs to be a more clever mechanism in place
# where there are MANY entity groups using different parent keys if Strong Consistency is required.
PARENT_KEY = ndb.Key("Entity", "moviequote_root")
class MainHandler(webapp2.RequestHandler):
def get(self):
template = jinja_env.get_template("templates/moviequotes.html")
'''self.response.write('Hello world!')'''
#moviequotes_query = MovieQuote.query().order(-MovieQuote.last_touch_date_time) NOT STRONG CONSISTENCY
moviequotes_query = MovieQuote.query(ancestor=PARENT_KEY).order(-MovieQuote.last_touch_date_time) # ASKING FOR THE ITEMS IN THE ROOT, WILL WAIT UNTIL ALL WORKS ARE DONE [STRONG CONSISTENCY]
self.response.write(template.render({'moviequotes_query': moviequotes_query}))
class AddQuoteAction(webapp2.RequestHandler):
def post(self):
logging.info(str(self.request))
quote = self.request.get('quote')
movie = self.request.get('movie')
# logging.info("Todo: Add Quote \"" + quote + "\" from movie \"" + movie + "\"")
# self.response.write("Todo: Add Quote \"" + quote + "\" from movie \"" + movie + "\"")
#new_moviequote = MovieQuote(parent = PARENT_KEY, quote=quote, movie=movie)
new_moviequote = MovieQuote(parent = PARENT_KEY,
quote=quote,
movie=movie)
new_moviequote.put()
self.redirect(self.request.referer)
class InsertQuoteAction(webapp2.RequestHandler):
def post(self):
quote = self.request.get('quote')
movie = self.request.get('movie')
if self.request.get("entity_key"):
# logging.info("URL Safe = \"" + self.request.get("entity_key") + "\"")
moviequote_key = ndb.Key(urlsafe=self.request.get("entity_key"))
# logging.info("String rep of REAL key = \"" + str(moviequote_key) + "\"")
moviequote = moviequote_key.get()
moviequote.quote = self.request.get("quote")
moviequote.movie = self.request.get("movie")
moviequote.put();
else:
new_moviequote = MovieQuote(parent = PARENT_KEY,
quote=quote,
movie=movie)
new_moviequote.put()
self.redirect(self.request.referer)
class DeleteQuoteAction(webapp2.RequestHandler):
def post(self):
moviequote_key = ndb.Key(urlsafe=self.request.get("entity_key"))
moviequote_key.delete()
self.redirect(self.request.referer)
app = webapp2.WSGIApplication([
('/', MainHandler),
('/addquote', AddQuoteAction),
('/insertquote', InsertQuoteAction),
('/deletequote', DeleteQuoteAction)
], debug=True)