why is my Python GAE code asynchronous?

Question

This is the code:

def create_game(user_id):
    game = classes.Games(user_id = user_id)
    game.put()

def get_game(user_id):
    game_query = classes.Games.gql('WHERE user_id = :1', user_id)

    game = False
    for item in game_query:
        game = item

    if not game:
        create_game(user_id)
        get_game(user_id)
    else:
        return game

def render_page(self):
    message = 'this is a game page<br>'.decode('utf-8')

    user = creditentials.get_user(self)
    if not user:
        self.redirect('/')
        return

    game = get_game(user.key().id())

    message += 'current game ID: '.decode('utf-8') + str(game.key().id())

    self.response.write(message)

I expect it to create just one instance of the game, instad it creates 10! Appearantly GQL query is perfromed asynchronously, and starting from the 3rd (?) instance of the get_game(user_id) it just skips game_query = classes.Games.gql('WHERE user_id = :1', user_id) line.

Am I right? How do I avoid this?

Answer 1

Queries aren't immediately consistent, so an entity that you've only just created won't be returned in a query performed right-away, you need to wait a bit.

In your case, you don't need to query for the entity - you just created it, so you know it exists, and can use it. Change your create_game function to return the new game, and then use that.

If you expect your user_id to be unique (and given your query, this seems to be the case) you could use it as the entity-id, then you can get-by-id instead of querying, which will strongly-consistent.

Check the "Data Consistency" section on this docs page for more detail on how queries work.