Hi Ben,
I've recently upgraded one of my busiest sites to use beaker 1.4.2 and
I am getting an intermittent error:
Module beaker.cache:115 in get
<< def get(self, key, **kw):
"""Retrieve a cached value from the container"""
return self._get_value(key, **kw).get_value()
get_value = get
>> return self._get_value(key, **kw).get_value()
Module beaker.container:269 in get_value
<< if not creation_lock.acquire(wait=False):
debug("get_value returning old value while new
one is created")
return value
else:
debug("lock_creatfunc (didnt wait)")
>> return value
UnboundLocalError: local variable 'value' referenced before assignment
I am using Memcached with the pure-python driver as the caching
backend. What we do is manually invalidate (delete) the cache under
certain circumstances. What is happening here as far as I can tell
is:
- the cache gets delted (using memcached's delete key functionality)
- the first request comes in where it gets regenerated
- while the cache is being regenerated, a second request comes in
and beaker tries to return the old value which no longer exists, even
though for some reason beaker thinks its there.
I understand this is to avoid the dog-pile effect, and would be the
correct thing to do if we still had the old cache.
Is delting the key not the way to go? Can I 'invlidate' the cache
some other way that preserves the anti-dogpile effect?
Also, should beaker not behave differently if there is no old value to
return?
Thanks,
Damian
> This bug has been fixed with a work-around in Beaker, and Beaker 1.4.2
> has been released with it.
>
> - Ben
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