Re: scalability

[Louis Mamakos <louie@...>]

On Apr 26, 2009, at 5:05 PM, Tobias Kieslich wrote:

> On Sun, 26 Apr 2009, gary ng wrote:
> > I believe that depends more on how to 'scale out' rather than scale  
> > within a single process(what libevent wants to solve) or machine.
> >
> > Almost all the containers(like apache, lighttpd etc.) can already  
> > handle the role of dispatching(massive connections) quite  
> > efficiently. I see no point implementing that in lua or other  
> > languages unless your need is very specific.
> I like to second that, when you hit 1,000+ connections, the sockets  
> are
> the least of your problem. Serving businesslogic to 1,000 clients  
> blows
> up a single server anyway and at that point you will have to look at
> horizontal scaling. That means you will have to run multiple  
> application
> servers proxied by something that can handle 1,000 + connections light
> lighttpd, nginx ... the usual suspects. It's probably not a good  
> idea to
> do that in Lua and server business logic from the same machine.
>
> 	-Tobias

There are other protocols and applications other than HTTP to web  
servers.  I don't
understand, for instance, how I'd use lighttpd to build an XMPP server  
that needs
to manage a large number of TCP connections.  Likewise, "business  
logic" need not
be a heavyweight operation that hits a database, or even a disk arm.   
An XMPP
server might have lightweight per-connection state in memory for a few  
thousand
sessions.

Using an alternative to select(), like kqueue() is a huge win because  
you don't
have to continually pass an indication of interest back and forth  
across the
kernel system call interface for each invocation.  A small change like  
this can
avoid a lot of complexity in your system in managing multiple  
instances of
an application.

louie