key collisions

mark rkmr.em at
Thu Feb 15 05:23:05 UTC 2007

Hi Dave,
I have not made much progress! I had the same problem of not being
able to reproduce in the test environment! But in production I
consistently get the problem!
So I moved to cmemcached
which is a python wrapper for the libmemcache. It seemed to solve the
problem at the beginning, but what was happening was if there was a
collision the app died with this message:

[FATAL at 1170222010.740685] mcm_fetch_cmd():1176: memcache(4) protocol
error: server sent data for key not in request

I have not fixed this problem yet! It seems to be the same problem as
before but the client here checking for consistency I think.

It will be great if someone can find a fix for this!

On 2/14/07, Dave St.Germain <dcs at> wrote:
> hi, mark,
> I'm having the same problem with key collisions with the python
> binding, and I was wondering if you've made any progress.  I haven't
> been able to reproduce the problem in a test, but in production,
> we'll encounter the problem all of a sudden after a while (the only
> "solution" so far is to restart memcached).  The server returns the
> wrong value for the requested key.  Not only that, but if you try a
> get_many for key 'foo', you may get a response that has key 'bar' and
> its value.
> Since I haven't been able to reproduce this behavior in a test, I
> don't yet know if it's the python binding or memcached itself.
> Does anyone have any ideas?
> Dave
> > Hi
> > I am consistently getting key collisions. There are total of around
> > 2000 key
> > value pairs cached.
> > This is how I prepare the key for memcached:
> > () where
> > key is the unique
> > id for the database row that I want to cache.
> > When I do a 'get' for a specific key, I get a value of a different
> > key.
> > I am using python-memcached as the client.
> > This is causing lot of problems. If anyone has faced similar issues
> > or has
> > any suggestions do reply.
> > cheers
> > mark

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