Re: Continuations

[Scott McKay <address@hidden>]

At 5:03 PM +0000 8/11/03, Paul Graham wrote:
>We had multiple servers.  (Yahoo Store now has over 100.)
>We just had users talk to a single server for the duration
>of their login session.  --pg

Unless you had a way of "persisting" the continuation state,
this just doesn't meet my definition of a "high availability"
web server architecture.  Did you do anything more sophisticated
to keep people from losing if, e.g., a server went down?

I personally don't see why a continuation, with its implicitly
captured state, is superior to having a session object that
explicitly captures the state.  The HotDispatch web site (also
written in Lisp, BTW) that I worked had very complex workflow,
and we found that objects worked just fine, and also worked
correctly in the face of load-balancing and crashed servers.

>--Evan Martin wrote:
>>  On Sun, 2003-08-10 at 20:21, Paul Graham wrote:
>>  > I argued this in my dissertation, but now I think I was wrong.
>>  > They're extremely useful for overcoming the statelessness of
>>  > CGI scripts.  See
>>  >
>>  > http://lib1.store.vip.sc5.yahoo.com/lib/paulgraham/bbnexcerpts.txt
>>
>>  I've read of other people doing similar things, and I think it's very
>>  cool, but I wondered:
>>  How can this scale to a large website, such as one with multiple
>>  independent web servers?
>>
>>  --
>>  Evan Martin
>>  martine@danga.com
>>  http://neugierig.org
>>