> Den 10/02/2015 kl. 17.15 skrev Erik Cederstrand <erik+li...@cederstrand.dk>:
>
> Hi list,
>
> I'm tracking down a bug in my app that shouldn't be happening with the
> transaction statements I added in my code. In my logging settings, I can set
> 'django.db.backends' to DEBUG to log the queries (I'm using the postresql
> backend). I see 'SAVEPOINT' statements logged, but I also need 'BEGIN' and
> 'COMMIT' so I can see when the transaction started and ended. How do I do
> that?
Hmm, I'm beginning to think I don't understand Django transactions. I have the
following two snippets, boiled down from my original code. The first one calls
cache methods via helper functions, the other one calls the cache methods
directly. If I run the code in parallel in two different processes, then the
first example asserts almost instantly, while the second example survives
several minutes. Can someone explain this?
import random
from django.db import transaction
from django.core.cache import cache
def get_val(key):
cache.get(key)
def set_val(key, val):
cache.add(key, val)
def del_val(key):
cache.delete(key)
# First example, fails
while True:
with transaction.atomic():
if not get_val('foo'):
print('no key found')
time.sleep(random.random())
if set_val('foo', 'bar'):
print('key added')
time.sleep(random.random())
else:
assert False
del_val('foo')
print('key deleted')
time.sleep(random.random())
# Second example, runs correctly
while True:
with transaction.atomic():
if not cache.get('foo'):
print('no key found')
time.sleep(random.random())
if cache.add('foo', 'bar'):
print('key added')
time.sleep(random.random())
else:
assert False
cache.delete('foo')
print('key deleted')
time.sleep(random.random())
Thanks,
Erik
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