пятница, 11 февраля 2011 г., 13:52:01 UTC+4 пользователь MarcMarc написал:
> Hi,
>
>
>
> My problem looks like this: when using memcached with fcgi on prefork
>
> mode I`m getting wrong values for a given keys. Values are
>
> dictionaries with keys, so I`m logging those erros like this:
>
>
>
> Memcached error: shops_categories.get_count.5942 -> {'version': None,
>
> 'value': 1328, 'key': 'shops_categories.get_count.5935', 'vkey':
>
> None}
>
>
>
> As shown above requested key was
>
> shops_categories.get_available_items_count.5942 and fetched value is
>
> wrong, key for given value is
>
> shops_categories.get_available_items_count.5935. Strange. This log is
>
> generated by custom method 'get', which contains no magic, its just a
>
> wrapper over django.core.cache.cache.get to log a key that was asked
>
> for and value that django.core.cache.cache.get fetched.
>
>
>
> There are some clues about this strange behaviour:
>
>
>
> - problem seems to be related to start/stop of the fcgi child process.
>
> When testing with 'ab -n 1000 -c 10' and runfcgi maxchildren=5 and
>
> maxrequests parameter set to 10 those errors are visible and almost
>
> constant, but set maxrequests to, let`s say, 100 000 and there are
>
> none of them.
>
>
>
> - most of the time mixed up values are similar, but this is not a
>
> rule. For instance:
>
>
>
> 11-02-11 09:50 aktywni.cache.utils ERROR utils: 23
>
> Memcached error: shops_categories.get_category_descendants.5650 ->
>
> {'version': None, 'value': 122, 'key':
>
> 'shops_categories.get_available_items_count.5650', 'vkey': None}
>
>
>
> 11-02-11 09:50 aktywni.cache.utils ERROR utils: 23
>
> Memcached error: shops_categories.get_available_items_count.5650 ->
>
> {'version': None, 'value': 1328, 'key':
>
> 'shops_categories.get_available_items_count.5935', 'vkey': None}
>
>
>
> 11-02-11 09:50 aktywni.cache.utils ERROR utils: 23
>
> Memcached error: shops_categories.get_category_descendants.5948 ->
>
> {'version': None, 'value': 0, 'key':
>
> 'shops_categories.get_available_items_count.5795', 'vkey': None}
>
>
>
> - single view generates around 25-50 cache requests, or even more.
>
>
>
> - when using get_multi tracebacks looks like this one:
>
>
>
> File "/var/www/htdocs/serwisy/aktywni.pl/lib/django/core/cache/
>
> backends/memcached.py", line 60, in get_many
>
> return self._cache.get_multi(map(smart_str,keys))
>
>
>
> File "/var/www/htdocs/serwisy/aktywni.pl/lib/memcache.py", line 738,
>
> in get_multi
>
> retvals[prefixed_to_orig_key[rkey]] = val # un-prefix returned
>
> key.
>
>
>
> KeyError: 'shops_categories.get_lowest_categories'
>
>
>
> - I`ve tested my site on threaded fcgi, and there is no such problem
>
> in
>
>
>
> Maybe there is some problem with connection to memcached left open
>
> after fcgi process is killed after set amount of requests? Maybe for
>
> some reason another request from next process is getting values from
>
> the already killed one? Of course there is no evidence of failure in
>
> memcached logs in verbose mode.
>
>
>
> Feel free to ask more questions, this is my first apperance on this
>
> group, I`ve tried to show every piece of evidence : )
>
>
>
> Env summary:
>
> Ubuntu 10.10 minimal (but there was the same problem on Gentoo)
>
> memcached 1.4.5
>
> python-memcached 1.43
>
> django 1.2.1
>
> nginx 0.7.67
Hello! So did you find the solution of this problem?
I have the same problem and it would be great if there is a real solutions.
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