#19519: Django fails to close db connections at end of request-response cycle
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Reporter: amosonn@… | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.4
(models, ORM) | Keywords: connection, managment,
Severity: Normal | closing, mysql, innodb, signal,
Triage Stage: Unreviewed | generator
Easy pickings: 0 | Has patch: 0
| UI/UX: 0
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Under some circumstances (I'll get to guesses about this in the end), the
db connection isn't closed at the end of the request, and resurfaces later
on to service another request. Thus, one request writes to the database,
and then the next request tries to look for that data and fails, because
it uses an outdated connection that hasn't yet been notified of the db
change (per [http://www.python.org/dev/peps/pep-0249/#connection-objects
pep-249], different connections aren't required to see the same data.) The
workaround solution for this is to add a django.db.connection.close()
before that query, which brings to mind
[https://code.djangoproject.com/ticket/13533 bug #13533]. Similarly, This
bug manifests on mysql innodb; but I haven't checked other databases, so
this might just be coincidence. It is also possible that the non-closing
connection bug exists for all back-ends, but that auto-commit isn't enough
to prevent the damage only on mysql innodb.
The situation under which I've seen these connections retained is when
sending an HttpResponse with a generator for content. It might be that
when sending such content, the following lines (django.db:44-47)
{{{
def close_connection(**kwargs):
for conn in connections.all():
conn.close()
signals.request_finished.connect(close_connection)
}}}
which are supposed to make sure the connection closes, don't work, because
the signal isn't raised. It is, however, still a riddle how the old
connection gets attached to a new request.
[https://code.djangoproject.com/ticket/19117 Bug #19117] might also be
related to this.
--
Ticket URL: <https://code.djangoproject.com/ticket/19519>
Django <https://code.djangoproject.com/>
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