[tbnl-devel] Re: TBNL Example

[Edi Weitz]

On Fri, 25 Feb 2005 22:35:18 +0100, Stefan Scholl <stesch at no-spoon.de> wrote:

> But I hope the session will be removed at some time, even when
> nobody tries to access an expired session?

Yes, see the code for SESSION-GC.  It will be removed at some time
unless nobody tries to access any session at all, whether expired or
not.

To make this more clear:

1. Whenever you try to access an expired session it will be
   automatically removed and thus your Lisp is free to garbage-collect
   it now.

2. Whenever any session whatsoever is accessed a global counter is
   increased and at certain intervals (there's a special variable for
   that but I don't think it's exported) all sessions which are
   expired will be removed even if their users haven't accesses them.

This implies that sessions might stay in the Lisp image for a long
time (although expired) /if/ there's no traffic /or/ if there's only
traffic that doesn't use sessions.

The alternative would be a separate thread which checks for expired
session independently of server traffic.  I think that's overly
complex, though, and the benefit of the current solution is that it
kind of automatically adapts to the server load.

Cheers,
Edi.