CODEWITHSUNDEEP
google-app-engineconcurrencygoogle-cloud-datastore
Tony the Pony
Tony the Pony

Reputation: 41447

GAE Datastore concurrency question

If two processes modify the same entity concurrently, but only modify different properties, can they potentially overwrite the changes made by the other process when calling DatastoreService.put?

Process A:

   theSameEntity.setProperty ("foo", "abc");
   DatastoreService.put (theSameEntity);

Process B:

   theSameEntity.setProperty ("bar", 123);
   DatastoreService.put (theSameEntity);

Upvotes: 1

Views: 246

Answers (2)

Stuart Mitchell
Stuart Mitchell

Reputation: 66

Yes, I have observed this (though in my case the concurrent requests modified the same property).

I don't think transactions will help because they don't lock the datastore they guarantee, that the operations in the transaction will see the same data. I Would like to know if anyone has found a solution to this.

Upvotes: 1

Cameron
Cameron

Reputation: 98856

Yes, it's possible they'll overwrite each other's changes, since the entire entity is sent to the datastore (serialized using protocol buffers) with each write (not just a diff).

You'll need to use transactions if you want to avoid this.

Upvotes: 3

Related Questions