Dan,

I'm pretty sure we're agreeing.

-jj

On 4/28/07, Dan <[EMAIL PROTECTED]> wrote:
>
>  IMHO.  I never implemented memcache, but the distributed memory concept is
> *not* by itself scalable architecture.  The key is session data.  Typically
> (as in default Pylons setup) session data is tied to physical hardware...
> your web server.  To make use of memcache, one would first need to implement
> scalable architecture, such as the 'share nothing' approach.
>
>  Again, I'm not claiming to be an expert on the 'share nothing'
> architecture, but my understanding is that 'share nothing' stores all data
> in the database... even session data.  This way, it doesn't matter what web
> server in your farm takes users requests.  They will all ask the database
> (the db will be your bottleneck) but at least they will *mostly* know how to
> access and store data.
>
>  So the basic point to my post is that scalable architecture is more about
> theory than specific tools.   The theory behind building scalable web
> applications is a growing subject in system engineering that I find
> interesting.  You can check a decent article about myspace.com struggles at
> - http://www.baselinemag.com/article2/0,1540,2084131,00.asp
>
>  'memcache' is a tool, when applied to a scalable architecture, could
> provide performance improvements.
>
>  Dan
>
>
>  Cliff Wells wrote:
>  On Fri, 2007-04-27 at 17:27 -0700, Shannon -jj Behrens wrote:
>
>
>  On 4/27/07, Cliff Wells <[EMAIL PROTECTED]> wrote:
>
>
>
>
>  Out of curiosity, how is this ugly? This should be mostly handled
> transparently by the proxy (i.e. sends same sessions to same backend).
>
>  If one Web server dies, all the users using that Web server lose their
> sessions. That sucks. It also limits the effectiveness of the load
> balancer. It can only redistribute *new* users instead of each new
> request.
>
>  Ah. Makes sense. I guess reading books *does* help!
>
>
>
>
>
>  or b) use a session server (less ugly).
>
>  And what do you recommend for this?
>
>  If I had to make the decision today, I'd probably use memcache.
>
>  mmm. Memcached rocks.
>
>
>
>
>
>  I've not seen this approach, so I'm
> curious (or maybe the proxy acts as a session server, so we're talking
> about the same thing?).
>
>  What do you mean the proxy acts as a session server? I don't know of
> any load balancers who can act as session servers.
>
>  I wasn't sure exactly what you meant by "session server", but now I do.
> So you are correct. I was thinking perhaps you meant "external process
> that maintains sessions across backends" in which case some load
> balancers do.
>
>
>
>
>  By the way, this topic is covered nicely in "Scalable Internet
> Architectures" and "Building Scalable Web Sites".
>
> (weird, de ja vu ;)
>
>  If only I had time to read actual books rather than bug people on the
> net for answers...
>
>
> Cliff
>
>
>
>
>
>  >
>


-- 
http://jjinux.blogspot.com/

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