# Copyright 2015 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.
"""
Sample application that demonstrates how to use the App Engine Memcache API.
For more information, see README.md.
"""
# [START gae_memcache_guestbook_all]
import cgi
import cStringIO
import logging
import urllib
from google.appengine.api import memcache
from google.appengine.api import users
from google.appengine.ext import ndb
import webapp2
class Greeting(ndb.Model):
"""Models an individual Guestbook entry with author, content, and date."""
author = ndb.StringProperty()
content = ndb.StringProperty()
date = ndb.DateTimeProperty(auto_now_add=True)
def guestbook_key(guestbook_name=None):
"""Constructs a Datastore key for a Guestbook entity with guestbook_name"""
return ndb.Key("Guestbook", guestbook_name or "default_guestbook")
class MainPage(webapp2.RequestHandler):
def get(self):
self.response.out.write("")
guestbook_name = self.request.get("guestbook_name")
greetings = self.get_greetings(guestbook_name)
stats = memcache.get_stats()
self.response.write("Cache Hits:{}
".format(stats["hits"]))
self.response.write("Cache Misses:{}
".format(stats["misses"]))
self.response.write(greetings)
self.response.write(
"""
""".format(
urllib.urlencode({"guestbook_name": guestbook_name}),
cgi.escape(guestbook_name),
)
)
# [START gae_memcache_guestbook_check_memcache]
def get_greetings(self, guestbook_name):
"""
get_greetings()
Checks the cache to see if there are cached greetings.
If not, call render_greetings and set the cache
Args:
guestbook_name: Guestbook entity group key (string).
Returns:
A string of HTML containing greetings.
"""
greetings = memcache.get("{}:greetings".format(guestbook_name))
if greetings is None:
greetings = self.render_greetings(guestbook_name)
try:
added = memcache.add(
"{}:greetings".format(guestbook_name), greetings, 10
)
if not added:
logging.error("Memcache set failed.")
except ValueError:
logging.error("Memcache set failed - data larger than 1MB")
return greetings
# [END gae_memcache_guestbook_check_memcache]
# [START gae_memcache_guestbook_query_datastore]
def render_greetings(self, guestbook_name):
"""
render_greetings()
Queries the database for greetings, iterate through the
results and create the HTML.
Args:
guestbook_name: Guestbook entity group key (string).
Returns:
A string of HTML containing greetings
"""
greetings = ndb.gql(
"SELECT * "
"FROM Greeting "
"WHERE ANCESTOR IS :1 "
"ORDER BY date DESC LIMIT 10",
guestbook_key(guestbook_name),
)
output = cStringIO.StringIO()
for greeting in greetings:
if greeting.author:
output.write("{} wrote:".format(greeting.author))
else:
output.write("An anonymous person wrote:")
output.write(
"{}
".format(cgi.escape(greeting.content))
)
return output.getvalue()
# [END gae_memcache_guestbook_query_datastore]
class Guestbook(webapp2.RequestHandler):
def post(self):
# We set the same parent key on the 'Greeting' to ensure each greeting
# is in the same entity group. Queries across the single entity group
# are strongly consistent. However, the write rate to a single entity
# group is limited to ~1/second.
guestbook_name = self.request.get("guestbook_name")
greeting = Greeting(parent=guestbook_key(guestbook_name))
if users.get_current_user():
greeting.author = users.get_current_user().nickname()
greeting.content = self.request.get("content")
greeting.put()
memcache.delete("{}:greetings".format(guestbook_name))
self.redirect("/?" + urllib.urlencode({"guestbook_name": guestbook_name}))
app = webapp2.WSGIApplication([("/", MainPage), ("/sign", Guestbook)], debug=True)
# [END gae_memcache_guestbook_all]