#33497: Database persistent connections do not work with ASGI in 4.0
-------------------------------------+-------------------------------------
Reporter: Stenkar | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 4.0
(models, ORM) |
Severity: Normal | Resolution: needsinfo
Keywords: ASGI; Database | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by Carlton Gibson):
* cc: Florian Apolloner, Andrew Godwin (added)
Comment:
Hi Stenkar.
Would you be able to put together a minimal test-project here, so that
folks can reproduce quickly.
This **may** be due to Django 4.0 having per-request contexts for the
thread sensitivity of `sync_to_async()` — See #32889.
If so, that's kind-of a good thing, in that too many open resources is
what you'd expect in async code, and up to now, we've not been hitting
that, as we've essentially been running serially.
Immediate thought for a mitigation would be to use a connection pool.
Equally, can we limit the number of threads in play using
[https://github.com/django/asgiref/blob/02fecb6046bb5ec0dbbad00ffcd2043e893fcea5/asgiref/sync.py#L303-L304
asgiref's `AGSI_THREADS` environment variable]? (But see
[https://github.com/django/daphne/issues/319#issuecomment-991962381 the
discussion on the related Daphne issue about whether that's the right
place for that at all].)
This is likely a topic we'll need to deal with (eventually) in Django:
once you start getting async working, you soon hit resource limits, and
handling that with structures for sequencing and maximum parallelism is
one of those hard-batteries™ that we maybe should provide. 🤔
--
Ticket URL: <https://code.djangoproject.com/ticket/33497#comment:4>
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