Transactions test

import logging
from google.appengine.ext import ndb, deferred
from webapp2 import RequestHandler, WSGIApplication


ENTITY_ID = 1


class MyModel(ndb.Model):
    prop = ndb.IntegerProperty(default=0)


def txn(key):
    entity = key.get()
    entity.prop += 1
    entity.put()


def defer_func():
    key = ndb.Key(MyModel, ENTITY_ID)
    ndb.transaction(lambda: txn(key), retries=0)


class TestHandler(RequestHandler):
    def get(self):
        MyModel(id=ENTITY_ID).put()
        for i in xrange(50000):
            deferred.defer(defer_func)


app = WSGIApplication([
    ('/test', TestHandler)
])