#15802: Django stops functioning when the database (PostgreSQL) closes the
connection
-------------------------------------+-------------------------------------
Reporter: Rick.van.Hattem@… | Owner:
Type: Bug | Honza_Kral
Component: Database layer | Status: reopened
(models, ORM) | Version: 1.3
Severity: Normal | Resolution:
Keywords: database, postgres, | Triage Stage: Accepted
postgresql, connection, closed | Needs documentation: 0
Has patch: 1 | Patch needs improvement: 1
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
-------------------------------------+-------------------------------------
Changes (by akaariai):
* cc: anssi.kaariainen@… (added)
* needs_better_patch: 0 => 1
Comment:
In normal HTTP serving situations the connection doesn't get stuck into
closed state. When the request is finished, the connections are closed and
the already committed .close() fix will remove the broken connection. I am
of course talking about 1.4 here, as it has the .close() fix already
applied.
However, if using the connection in a long running task, then there will
be problems. In that setting, the connection is usually never closed. We
should really document that you should call connection.close() after you
are done with it. Actually, we should document how to safely use Django's
connections in task-running setting, I don't think we have that and there
are multiple potential problems in that setting (Idle in TX for example).
The attached patch doesn't apply cleanly (15802-2.diff). It doesn't apply
to the base directory, and even if applied into the django/ directory, it
doesn't apply cleanly. In addition, if I am reading it correctly it is
downright dangerous. I think what happens is this.
{{{
obj.save() # succeeds
# connection is closed for some reason
obj.save() # Hey, ._cursor() gave me a new connection! No error raised
anywhere, perhaps I am even in a different transaction...
}}}
I don't believe there to be any safe way to automatically create a new
connection without the user calling .close() in between. Surprising things
could happen otherwise. The only possible exception would be that when
leaving transaction management the connection could be closed on error.
This could also help in many situations, because usually when you get an
error (possibly due to closed connection), you will rollback the
transaction (leave transaction management), and thus the connection would
get unstuck.
Still one helpful thing would be to return a consistent
`ConnectionClosedError` when the connection is closed outside Django's
control.
In short: I don't think there is anything to do to get this into 1.4. Too
big changes required. The only solution you have is somehow detecting
closed connections in your code and closing the connection manually in
those cases.
--
Ticket URL: <https://code.djangoproject.com/ticket/15802#comment:20>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" 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/django-updates?hl=en.
