Mike,
As of version 1.6, Django supports persistent
DB connections
(connection pooling). CONN_MAX_AGE specifies
the number of
seconds that a connection will remain open and
be reused.
You can set it to 0 to cause each DB
interaction to open, use,
and close its own connection. You can set it
to None to allow
an unlimited number of connections. See:
-
https://docs.djangoproject.com/en/dev/ref/databases/
However, the behavior you're seeing doesn't
seem to match this
documented behavior. I'd have expected
CONN_MAX_AGE = 0
to prevent connections from being reused, so
they should be
closed at the end of the request that used
them. So, unless you
have 65 or more concurrent requests, you
should not be hitting
your limit.
I'm not surprised that CONN_MAX_AGE = None has
an effect, but
I wouldn't have been able to predict whether
it makes things
better or worse. It allows Django to reuse
connections so fewer
of them should be created, but it also allows
Django to pool them
for as long as it likes, so a large number of
them may accumulate.
Have you tried any other values for
CONN_MAX_AGE, like 1 or 2?
Also, are you using the Django development
server? The docs
linked above say:
"The development server creates a new
thread for each request
it handles, negating the effect of
persistent connections.
Don’t enable them during development."
On 1/17/17 2:25 PM, Michael Grundler
wrote:
When
Django closes a database connection at
the end of a request/response cycle does
that connection still maintain its hold
on the database?
I
ask because I am running an app on a
spatialite (v4.3.0a) database, which,
due to a limitation in the GEOS library
(v3.6.1-CAPI-1.10.1 r0), can only accept
a maximum of 64 connections. When I
configure Django so that CONN_MAX_AGE =
0, the server log will eventually begin
filling up with messages that read
"ERROR: Too many connections: max 64".
If I enable persistent connections by
setting CONN_MAX_AGE = None, these
messages disappear. To me this suggests
that when Django closes a connection at
the end of a request/response cycle that
connection persists from spatialite's
perspective.
Is
this expected behavior?
The
error message is easily reproduced by
starting a project configured to use
spatialite, logging into the admin page,
and then refreshing your browser
repeatedly until 64 requests have been
made.
Thanks
for any insights,
Mike
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