#18984: TransactionTestCase._fixture_teardown locks under mysql
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Reporter: jdunck | Owner: aaugustin
Type: Bug | Status: new
Component: Testing framework | Version: master
Severity: Release blocker | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by aaugustin):
I finally managed to reproduce the problem with `TransactionTestCase` and
`TEST_MIRROR` but without `multi_db = True`.
In order to create a pending transaction, I made a raw SQL query and
didn't call `commit_unless_managed()`. This is obviously incorrect, but I
can imagine this sequence happening accidentally — for instance if an
exception is raised in a test before calling `commit_unless_managed()`.
I've attached a test case as a patch, but I don't intend to commit it, for
the reasons explained above.
----
To fix the problem, I had to `rollback_unless_managed()` all connections,
and not only the default connection like the pull request does, because
`multi_db = False`. I think the PR worked for Jeremy's case because he
only had a pending transaction on the default connection. If so, rolling
back the transaction on the default connection was enough.
Of course, if I had set `multi_db = True`, the PR would have rolled back
the transactions on all databases. But currently that doesn't work at all.
I think it's best to avoid deadlocks even in the case of programming
mistakes, and calling `rollback_unless_managed()` is inexpensive when the
connection hasn't been used.
I've also attached a patch that implements this solution.
----
I propose to commit this patch and open a new ticket for the
`TransactionTestCase` + `TEST_MIRROR` + `multi_db = True` combination.
--
Ticket URL: <https://code.djangoproject.com/ticket/18984#comment:9>
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