#23642: LocMemCache.incr is not thread safe
-------------------------------------+-------------------------------------
Reporter: tchaumeny | Owner: nobody
Type: Bug | Status: new
Component: Core (Cache system) | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage:
Has patch: 0 | Unreviewed
Needs tests: 0 | Needs documentation: 0
Easy pickings: 0 | Patch needs improvement: 0
| UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by tchaumeny):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> `LocMemCache` is documented as being thread-safe, but its `incr`
> operation isn't: there is not lock wrapping the whole get+set operation.
>
> The code below demonstrates the issue:
>
> {{{
> import threading
>
> from django.core.cache.backends.locmem import LocMemCache
>
> cache = LocMemCache('test', {})
>
> cache.set('foo', 0)
>
> def increment(key):
> cache.incr(key)
>
> threads = []
> for i in range(20):
> t = threading.Thread(target=increment, args=('foo',))
> t.start()
> threads.append(t)
>
> for t in threads:
> t.join()
>
> print cache.get('foo') # Random results — 20 is expected
> }}}
New description:
`LocMemCache` is documented as being thread-safe, but its `incr` operation
isn't: there is no lock wrapping the whole get+set operation.
The code below demonstrates the issue:
{{{
import threading
from django.core.cache.backends.locmem import LocMemCache
cache = LocMemCache('test', {})
cache.set('foo', 0)
def increment(key):
cache.incr(key)
threads = []
for i in range(20):
t = threading.Thread(target=increment, args=('foo',))
t.start()
threads.append(t)
for t in threads:
t.join()
print cache.get('foo') # Random results — 20 is expected
}}}
--
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Ticket URL: <https://code.djangoproject.com/ticket/23642#comment:1>
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