helloworld.py

from google.appengine.ext import db
from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
import random

class SimpleCounterShard(db.Model):
  count = db.IntegerProperty(required=True, default=0)

NUM_SHARDS = 10

def get_count():
  total = 0
  for counter in SimpleCounterShard.all():
    total += counter.count
  return total

def increment():
  def txn():
    index = random.randint(0, NUM_SHARDS - 1)
    shard_name = "shard" + str(index)
    counter = SimpleCounterShard.get_by_key_name(shard_name)
    if counter is None:
      counter = SimpleCounterShard(key_name=shard_name)
    counter.count += 1
    counter.put()
  db.run_in_transaction(txn)

class IncrementPage(webapp.RequestHandler):
  def get(self):
    increment()

class CounterPage(webapp.RequestHandler):
  def get(self):
    self.response.out.write("Hello, %d!" % (get_count(), ))

class DeletePage(webapp.RequestHandler):
  def get(self):
    for counter in SimpleCounterShard.all():
      counter.delete()

application = webapp.WSGIApplication([('/', CounterPage), ('/inc/', IncrementPage), ('/delete/', DeletePage)])

def main():
  run_wsgi_app(application)

if __name__ == "__main__":
  main()