I'd like to guarantee a transaction runs once, and once only. Let's
say I'm simulating a bank transfer of $5 from AccountA to AccountB.
The normal transaction is not idempotent:
Repeat until success {
* start txn
* debit $5 from AccountA
* credit $5 to AccountB
* commit txn
}
If this inadvertently runs multiple times, I will have very unhappy
customers. Maybe I should do this:
Create TxnID entity instance
Repeat until success {
* start txn
* load TxnID (if null, return success immediately)
* debit $5 from AccountA
* credit $5 to AccountB
* delete TxnID
* commit txn
}
With the pain of adding a third entity to my XG transaction (and a
cron that prunes really old, abandoned TxnIDs) it seems that I this
does the trick. Or am I missing something? Is this the best way to
accomplish once-only transactions? Is there an alternative approach?
Thanks in advance,
Jeff
--
You received this message because you are subscribed to the Google Groups
"Google App Engine" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/google-appengine?hl=en.
