[Django] #32747: CacheHandler logic issue
Django
-----------------------------------------------+------------------------
Reporter: Alexander Ebral | Owner: nobody
Type: Bug | Status: new
Component: Core (Cache system) | Version: 3.2
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-----------------------------------------------+------------------------
After the commit:
https://github.com/django/django/commit/98e05ccde440cc9b768952cc10bc8285f4924e1f
logic of the method "all" from CacheHandler class was changed.
Before:
{{{
def all(self):
return getattr(self._caches, 'caches', {}).values()
}}}
This method returned connections that were created in !__getitem!__
Now:
{{{
def all(self):
return [self[alias] for alias in self]
}}}
Connections return for all "CACHES" from settings.py (in case of absence
- they are forcibly created in self[alias])
Which version of this method seems to be right?
In my case this unnecessary mass initialization of custom diskcache-
classes leads to io-lags.
Snippet that helped me:
{{{
import django.core.cache
def cache_getitem(self, alias, exists_only=False):
try:
return getattr(self._connections, alias)
except AttributeError:
if alias not in self.settings:
raise self.exception_class(f"The connection '{alias}' doesn't
exist.")
if exists_only:
return
conn = self.create_connection(alias)
setattr(self._connections, alias, conn)
return conn
def cache_all(self):
connections = [self.__getitem__(alias, exists_only=True) for alias in
self]
return [conn for conn in connections if conn is not None]
django.core.cache.CacheHandler.all = cache_all
django.core.cache.CacheHandler.__getitem__ = cache_getitem
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/32747>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Django
-------------------------------------+------------------------------------
Reporter: Alexander Ebral | Owner: nobody
Type: Bug | Status: new
Component: Core (Cache system) | Version: 3.2
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Mariusz Felisiak):
* cc: Florian Apolloner (added)
* severity: Normal => Release blocker
* stage: Unreviewed => Accepted
Comment:
Thanks for the report. I agree this can cause a performance regression, we
shouldn't initialize unused caches unnecessarily. As far as I'm aware we
can restore the previous behavior with:
{{{
diff --git a/django/core/cache/__init__.py b/django/core/cache/__init__.py
index 05ef3897d0..c008ed1125 100644
--- a/django/core/cache/__init__.py
+++ b/django/core/cache/__init__.py
@@ -43,6 +43,8 @@ class CacheHandler(BaseConnectionHandler):
) from e
return backend_cls(location, params)
+ def all(self):
+ return [self[alias] for alias in self if
hasattr(self._connections, alias)]
caches = CacheHandler()
}}}
Regression in 98e05ccde440cc9b768952cc10bc8285f4924e1f.
--
Ticket URL: <https://code.djangoproject.com/ticket/32747#comment:1>
Django
Reporter: Alexander Ebral | Owner: Mariusz
| Felisiak
Type: Bug | Status: assigned
Component: Core (Cache system) | Version: 3.2
Keywords: | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Mariusz Felisiak):
* owner: nobody => Mariusz Felisiak
* status: new => assigned
--
Ticket URL: <https://code.djangoproject.com/ticket/32747#comment:2>
Django
-------------------------------------+-------------------------------------
Reporter: Alexander Ebral | Owner: Mariusz
| Felisiak
Type: Bug | Status: assigned
Keywords: | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Mariusz Felisiak):
* has_patch: 0 => 1
Comment:
[https://github.com/django/django/pull/14395 PR]
--
Ticket URL: <https://code.djangoproject.com/ticket/32747#comment:3>
Django
-------------------------------------+-------------------------------------
Reporter: Alexander Ebral | Owner: Mariusz
| Felisiak
Component: Core (Cache system) | Version: 3.2
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Mariusz Felisiak <felisiak.mariusz@…>):
* status: assigned => closed
* resolution: => fixed
Comment:
In [changeset:"958cdf65ae90d26236d1815bbba804729595ec7a" 958cdf65]:
{{{
#!CommitTicketReference repository=""
revision="958cdf65ae90d26236d1815bbba804729595ec7a"
Fixed #32747 -- Prevented initialization of unused caches.
Thanks Alexander Ebral for the report.
Regression in 98e05ccde440cc9b768952cc10bc8285f4924e1f.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/32747#comment:4>
Django
-------------------------------------+-------------------------------------
Reporter: Alexander Ebral | Owner: Mariusz
| Felisiak
Type: Bug | Status: closed
Keywords: | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Comment (by Mariusz Felisiak <felisiak.mariusz@…>):
In [changeset:"41e2aa7eb24e564f6984e6e6660b8e5ff5edbd9d" 41e2aa7]:
{{{
#!CommitTicketReference repository=""
revision="41e2aa7eb24e564f6984e6e6660b8e5ff5edbd9d"
[3.2.x] Fixed #32747 -- Prevented initialization of unused caches.
Thanks Alexander Ebral for the report.
Regression in 98e05ccde440cc9b768952cc10bc8285f4924e1f.
Backport of 958cdf65ae90d26236d1815bbba804729595ec7a from main
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/32747#comment:5>