guestbook.py

import logging
import os

import jinja2
import webapp2
from google.appengine.api import users
from google.appengine.ext import ndb
from google.appengine.api import memcache


# We set a parent key on the 'Greetings' to ensure that they are all in the same
# entity group. Queries across the single entity group will be consistent.
# However, the write rate should be limited to ~1/second.

def guestbook_key(guestbook_name='default_guestbook'):
    return ndb.Key('Guestbook', guestbook_name)

jinja_environment = jinja2.Environment(
    loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
    extensions=['jinja2.ext.autoescape'],
    autoescape=True)


class Greeting(ndb.Model):
    author = ndb.UserProperty()
    content = ndb.StringProperty(indexed=False)
    date = ndb.DateTimeProperty(auto_now_add=True)


class MainPage(webapp2.RequestHandler):
    def get(self):
        guestbook_name = self.request.get('guestbook_name', 'default_guestbook')
        greetings = memcache.get('%s:greetings' % guestbook_name)
        if not greetings:
            greetings_query = Greeting.query(ancestor=guestbook_key(guestbook_name)).order(-Greeting.date)
            greetings = greetings_query.fetch(10)
            if not memcache.set('%s:greetings' % guestbook_name, greetings):
                logging.error('Memcache set failed in GET.')

        if users.get_current_user():
            url = users.create_logout_url(self.request.uri)
            url_linktext = 'Logout'
        else:
            url = users.create_login_url(self.request.uri)
            url_linktext = 'Login'

        template = jinja_environment.get_template('index.html')
        self.response.out.write(template.render(greetings=greetings,
                                                url=url,
                                                url_linktext=url_linktext))


class Guestbook(webapp2.RequestHandler):
    def post(self):
        guestbook_name = self.request.get('guestbook_name', 'default_guestbook')
        greeting = Greeting(parent=guestbook_key(guestbook_name))

        if users.get_current_user():
            greeting.author = users.get_current_user()

        greeting.content = self.request.get('content')
        greeting.put()
        greetings = memcache.get('%s:greetings' % guestbook_name)
        if greetings:
            greetings.append(greeting)
            if not memcache.set('%s:greetings' % guestbook_name, greetings):
                    logging.error('Memcache set failed in POST.')
        self.redirect('/')

application = webapp2.WSGIApplication([
    ('/', MainPage),
    ('/sign', Guestbook),
], debug=True)