CODEWITHSUNDEEP
google-app-engineapp-engine-ndbgoogle-app-engine-python
alzy
alzy

Reputation: 307

Google App Engine ndb: Order of mixed sync and async operations

When using Google App Engine ndb, do I have to worry about mixing synchronous and asynchronous put operations in the same function?

e.g. Say that I have some code like this:

class Entity(ndb.Model):
  some_flag = ndb.BooleanProperty()


def set_flag():
  ent=Entity()

  ent.some_flag = False
  ent.put_async()

  ent.some_flag = True
  ent.put()

Does that datastore take care of ensuring that all pending async writes are applied before the synchronous write (so that after set_flag runs, it is guaranteed that the flag will be True)? Or is there a race condition because the async put might complete after the synchronous put?

Upvotes: 1

Views: 101

Answers (2)

George
George

Reputation: 1516

For sample code, and a practical solution, you may have a look at Dan McGrath's reply to the "Cloud Datastore: ways to avoid race conditions" question.

Upvotes: 0

minou
minou

Reputation: 16563

No, the datastore does not take care of this for you.

Even with synchronous puts, calls from different threads can overwrite each other.

I recommend that you read up a bit on transactions, and when and why there are helpful.

Upvotes: 2

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