Date: Fri, 2 Feb 2001 09:54:38 -0800 (PST) From: John Polstra <jdp@polstra.com> To: hackers@freebsd.org Cc: julian@elischer.org Subject: Re: CVSup7.FreeBSD.org is back in service Message-ID: <200102021754.f12Hscu03043@vashon.polstra.com> In-Reply-To: <3A79145A.39CF9671@elischer.org> References: <200101312315.f0VNFwR04246@vashon.polstra.com> <3A79145A.39CF9671@elischer.org>
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In article <3A79145A.39CF9671@elischer.org>, Julian Elischer <julian@elischer.org> wrote: > > I have the folowing suggestion for CVSup.. > the ability to specify several servers. > Cvsup can have a quick exchange with each to inquire about load and check the > latency and bandwidth > and the last time updated, and choose the best.... > Since you control both ends this is possible.. This is a frequently requested feature, but I've always been reluctant to provide it. Human nature being what it is, I'm afraid soon everybody would have 15 servers listed in their supfiles. So 15 servers would get hit on each update instead of just one. It is true that the load query wouldn't hit the servers nearly as hard as an actual update. But it would require forking a process at least. (Yes, it could be done by creating a thread, but experience has shown that to be a bad idea. All you need is one client doing something weird to trigger a bug in the server, and poof, the master server has crashed. It's a lot safer to isolate each client in its own process as quickly as possible.) Also, the loads on the mirrors I've observed vary erratically and rapidly. Servers can and do go from 20 clients to 3 clients in a matter of seconds. So the results of a load query 15 seconds ago aren't all that valuable, nor are figures representing load averages over time. I would rather leave load balancing out of the CVSup protocol and have it implemented by other means. The folks who run the mirrors in Japan have a very nice setup which uses SNMP to query the number of active CVSup clients on each mirror. They don't do automatic load balancing with it currently, but they make some nice graphs available on the web for people to use. (Sorry, I don't remember the URL.) John -- John Polstra jdp@polstra.com John D. Polstra & Co., Inc. Seattle, Washington USA "Disappointment is a good sign of basic intelligence." -- Chögyam Trungpa To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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