#19707: TransactionMiddleware leaks transaction state
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Reporter: akaariai | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 1.4
(models, ORM) | Resolution: fixed
Severity: Release blocker | Triage Stage: Accepted
Keywords: | Needs documentation: 0
Has patch: 0 | Patch needs improvement: 1
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
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Comment (by akaariai):
One way a rollback might fail is if a connection goes away in the middle
of a request. I just tried (using the attached test project), and if a
connection goes away between the testapp.views.view create() and finishing
the request, then the rollback will fail on MySQL. And, if there is no
try-except, then the connection will leak transaction state. psycopg2
actually manages this situation correctly and the rollback() and close()
will succeed. As a complete shocker mysql doesn't. Now, dropped db
connections are rare, but they are something Django should survive.
Unfortunately the DB API 2 has nothing guaranteeing that rollback() and/or
close() will not raise exceptions in this case.
(To reproduce, place a breakpoint after the testapp.views.view create(),
shut down the dbserver, continue the request).
Raise is a good idea, but only after all the connections have been looped
through, otherwise the later connections might leak state. Would
log.exception() to request log be good enough?
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Ticket URL: <https://code.djangoproject.com/ticket/19707#comment:14>
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