From owner-freebsd-net Wed Apr 17 16:50:20 2002 Delivered-To: freebsd-net@freebsd.org Received: from patrocles.silby.com (d84.as9.nwbl0.wi.voyager.net [169.207.132.212]) by hub.freebsd.org (Postfix) with ESMTP id DB6F637B404 for ; Wed, 17 Apr 2002 16:50:13 -0700 (PDT) Received: from patrocles.silby.com (localhost [127.0.0.1]) by patrocles.silby.com (8.12.2/8.12.2) with ESMTP id g3I5nnLx017543; Thu, 18 Apr 2002 00:49:49 -0500 (CDT) (envelope-from silby@silby.com) Received: from localhost (silby@localhost) by patrocles.silby.com (8.12.2/8.12.2/Submit) with ESMTP id g3I5nj8O017540; Thu, 18 Apr 2002 00:49:47 -0500 (CDT) X-Authentication-Warning: patrocles.silby.com: silby owned process doing -bs Date: Thu, 18 Apr 2002 00:49:45 -0500 (CDT) From: Mike Silbersack To: Mark Delany Cc: Bill Fenner , Subject: Re: What does FreeBSD do when listen queue is full ? In-Reply-To: <20020417213805.A91259@bushwire.net> Message-ID: <20020418004301.K17506-100000@patrocles.silby.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On Wed, 17 Apr 2002, Mark Delany wrote: > Are we discussing what happens when the number of pending connections > exceeds the backlog? If the suggestion is to leave such connections > pending then the question becomes what's the real purpose of backlog? Yes, that is what we're discussing. > For arguments sake, say I have a web server that I know handles 10 > requests per second and I want to offer a 2 second response time. To > do this I set the backlog to 20 on each of the web servers and > configure the load balancer to periodically check each server by > attempting to establish a session. > > If the load balancer connection attempt fails then it knows that that > particular server already has 2 seconds worth of work so it should not > consider that server as available at the moment (note that some load > balancer configurations mean that connection counting is not possible > and, oftentimes they don't do so accurately anyway). Well, 4.5+ would already be considered broken by your standards; it does not send a RST when dropping connections that have exceeded the backlog. I understand your method, but it seems perhaps a bit too simplistic. Have you considered having the load balancer make a simple request (fetching a static piece of html) every .25 seconds or so? The total response time from such connections would presumably give you a much better picture of how loaded the server is. If we do go ahead and make the changes that Bill proposes, it should be possible to add a sysctl that would cause a RST to be emitted rather than the connection to be returned to the syncache. Mike "Silby" Silbersack To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message