#35757: memcached.PyMemcacheCache reentrancy problem with ASGI-based runserver
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Reporter: Harm Verhagen | Owner: (none)
Type: Uncategorized | Status: closed
Component: Uncategorized | Version: 5.1
Severity: Normal | Resolution: invalid
Keywords: | 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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Comment (by Harm Verhagen):
I reproduced this problem with a small Django project.
It seems to be related with channels (v3)
Please advise, if Django related (if so, could you reopen the ticket?)
I created a new project according the to polls example. The problem occurs
when adding 'channels' to `INSTALLED_APPS` (without even using channels).
polls.views.py
{{{#!python
from django.http import HttpResponse
from django.core.cache import cache
def incr():
key = 'example:key'
try:
val = cache.incr(key, 1)
except ValueError:
cache.set(key, 1)
val = 1
return val
def index(request):
v = incr()
return HttpResponse("Hello, world. You're at the polls index. %d" % v)
}}}
settings.py
{{{#!python
CACHES = {
'default': {
'BACKEND': 'django.core.cache.backends.memcached.PyMemcacheCache',
# 'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
# using LocMemCache 'fixes' the problem
'LOCATION': "localhost:11211"
},
}
INSTALLED_APPS = [
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'channels', # adding this line shows the problem, removing
this line 'fixes' the problem
]
ASGI_APPLICATION = "mysite.asgi.application" # required for
channels
}}}
Steps to reproduce, run the following script get_parallel.sh
{{{#!bash
#!/bin/bash
#
# do requests in parallel
#https://code.djangoproject.com/ticket/35757
url='http://localhost:8000/polls/'
curl $url&
curl $url&
curl $url&
curl $url
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/35757#comment:12>
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