#34865: DatabaseWrapper are not GC and connections are not closed
-------------------------------------+-------------------------------------
Reporter: Fábio Domingues | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Fábio Domingues):
Tested using Uvicorn and Daphne, the database engine should not matter, I
tested with PostgreSQL, `CONN_MAX_AGE` could be any value and the effect
is the same using ''async'' or ''sync'' views.
{{{#!python
get_refs = lambda: [o for o in gc.get_objects() if isinstance(o,
BaseDatabaseWrapper)]
plot_refs = lambda: objgraph.show_backrefs(get_refs(), filename="sample-
graph.png")
def sync_view(request):
MyModel.objects.count()
# gc.collect()
# plot_refs()
return HttpResponse(f"Number of BaseDatabaseWrapper instances:
{len(get_refs())}")
async def async_view(request):
await MyModel.objects.acount()
# gc.collect()
# plot_refs()
return HttpResponse(f"Number of BaseDatabaseWrapper instances:
{len(get_refs())}")
}}}
On each refresh you should see the number of instances increase. If you
plot the references you would see many diagrams like the one in the
attachment. Throwing `gc.collect()` actually get it, but it take some
milliseconds, even if the underlying database connection is already
closed.
--
Ticket URL: <https://code.djangoproject.com/ticket/34865#comment:5>
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