CODEWITHSUNDEEP
google-app-enginegoogle-cloud-datastore
iamkhush
iamkhush

Reputation: 2592

GAE Race condition .get() and .put()

I am saving one of the fields in datastore using:

self.user.expiration_date = datetime.datetime.utcnow() + datetime.timedelta(days=31)
self.user.put()

I am using Webapp2. After saving the user expiration date, I redirect the user to a method, where the following code is written.

user = User.all().filter('email =', self.session.get('email'))

digest = self.session.get('passwd').encode('utf-8', 'ignore')
user = user.filter('passwd =', digest).get()
self.user = user

However, after this, when I check for the expiration_date, its Null or previous value.

What should I do here to get correct value?

Upvotes: 0

Views: 101

Answers (1)

Josh J
Josh J

Reputation: 6893

You are seeing the effects of Eventual Consistency in a NoSQL Datastore. This section explains what is up. https://cloud.google.com/datastore/docs/articles/balancing-strong-and-eventual-consistency-with-google-cloud-datastore/#h.w3kz4fze562t

Basically there is a slight delay between when an entity is written and when those writes will be seen by a query. If you refetch the entity by its key, you will avoid this problem.

If you can replace the User.all() query with a User.get_by_id() call and then compare user.email == session.get('email') and user.password == digest then you can avoid it.

Upvotes: 1

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