On Dec 30, 6:09 pm, Tycon <[email protected]> wrote:
> Let me clarify that using memcached in beaker doesn't work ONLY FOR
> STORING SESSIONS.
>
> It does work for regular caching in beaker (e.g. using @beaker_cache
> decorator
> to cache controller actions etc).
>
> This is not a bug, it's basically an incorrect implementation, which
> uses wrong design and is completely untested. For storing sessions in
> mecached you need to do the same thing as when storing session in a
> file - pickle the session and store it as a single key in memcached.
> So you can update or remove the session object in a single mecached
> call, and all the sessions attributes will have the same expiration.
> Storing each session attribute as a separate record is incorrect
> because memcached doesn't allow you to update/iterate/delete groups of
> records together.
I'd like to add that the current incorrect memcached/Session
implementation is preferable to the previous implementation, in that
it fails immediately. The old version *would* appear to work since it
would store an additional element in memcached which consisted of all
the keys for a particular namespace, thereby allowing namespace.keys()
to work. But if the cache started pruning its data, then you'd get
random holes in your session data, or perhaps the list of keys() would
be pruned causing a similar failure to the one you have...but only
after many hours/days of uptime.
That the file-based storage stores the session as a pickled dictionary
is an implementation detail of that backend. So once the Session is
modified to be appropriate against memcached, it would store a single
key in a session-id corresponding namespace, containing the session
dictionary (the Python memcached API does the pickling for us). Its
important that the namespace name is associated with the session id,
as opposed to using a constant namespace for all sessions - since in
file-based land, the namespace corresponds to a single file, and it
wouldn't perform very well to have all user sessions stored in a
single giant file with a single pickled dict inside.
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