Re: Connection limiting & Sorry servers

On Wed, 2009-08-05 at 18:26 +0200, Willy Tarreau wrote:
> On Wed, Aug 05, 2009 at 05:52:50PM +0200, Bo??tjan Mer??un wrote:
> > Hi Willy
> >
> > On Mon, 2009-08-03 at 09:21 +0200, Willy Tarreau wrote:
> >
> > > why are you saying that ? Except for rare cases of huge bugs, a server
> > > is not limited in requests per second. At full speed, it will simply use
> > > 100% of the CPU, which is why you bought it after all. When a server dies,
> > > it's almost always because a limited resource has been exhausted, and most
> > > often this resource is memory. In some cases, it may be other limits such
> > > as sockets, file descriptors, etc... which cause some unexpected exceptions
> > > not to be properly caught.
> >
> > We have a problem that our servers open connections to some 3rd party,
> > and if we get too many users at the same time, they get too many
> > connections.
>
> So you're agreeing that the problem comes from "too many connections". This
> is exactly what "maxconn" is solving.

The whole story is like that: during the process on our servers, we have to open a few connections for every user to some 3rd party and the process for the user finishes.
If any of the connections is unsuccesful, so is everything that user did before that (if he does not try again and eventually succeeds). The 3rd party limits total concurrent connections and connections per second.
The number of connections that users make to the 3rd party depends on what users do on our pages. User can just browse the site for 10 minutes and open no connections or he can finish his process in a minute and open more then 10 connections during that time.

As you probably see, my problem is the difference between the user, that comes the check the site and the user that knows exactly what he wants on the site.

The factor is at least 20 (probably more) which means that one setting is not good for all scenarios, either it will be to high and users will flood the 3rd patry with too many connections or few users will be able to browse the site and the rest will wait even though server will be sleeping.

I know that these problems should be solved on different levels like application, 3rd party connection limiting etc... but the problem is actually more of political nature and what I am trying to do is just solving the current situation with the tools and options I have. One of them is HAProxy and it's connection limiting and with it I would like to help myself as much as I can.

I hope that clarified my situation a bit.

I will not be able to test anything for a week or more likely two, but I will continue as soon as possible and if I come to any useful conclusions, I will also notify the list.

Thank you again and best regards

                Bostjan