[Zope] resolving conflict errors

[Dieter Maurer]

Dennis Allison wrote at 2005-12-8 18:29 -0800:
> ...
>The problem I am trying to resolve appears to be load related.  The
>observed symptom is that (some) session variables spontaneously disappear.  

It is very surprising that some (!) session variables should
spontaneously disappear -- in fact it is unbelievable.

  The session machinery has in no way any preference for
  some variable stored in the session. They are all treated
  in the same way. It looks almost impossible that some
  variables vanish spontaneously while others remain.

The following is quite normal (for buggy applications):

     The value of session variables seems to be reset spontaneously.

     This happens when the value is a mutable object and
     the mutable object is mutated without a notice for the session.

     Then, the modified value is available in this cache
     (until the session is flushed from it). Other caches
     see the old value.
     Because it is apparently non-deterministic which cache
     is used for a request, the observed session value
     seems to switch between different values.

It might be possible (though I have never seen a hint towards this)
that due to some bug the session is reset to an earlier state
(which did not yet have the session variables you now miss).
In this case, you should not only see some variables missing but
the others to have (potentially) outdated values.


-- 
Dieter