We use chef and ohai which talks to AWS to calculate node counts for servers based off tags and metadata. We then have a cookbook that generates the haproxy.cfg every time chef runs (on a cron). If the file changes we reload the config which seems to keep the sessions alive.
There are far simpler ways to achieve the above. For instance a really simple bash script that echo's static content to haproxy.cfg and the amazon command line tools feeding a for loop that prints out the server lines with their options. Having said all of this.. I think it would be cool to allow a file based backend. What I mean by that is that I would prefer to generate backend files and upon those files changing haproxy would automatically load them. So for instance on my static backend I may update the static.servers file which is referenced in haproxy.cfg. I believe you can do similar things with mod_jdk and apache. On 9 January 2013 22:47, Kevin Heatwole <ke...@heatwoles.us> wrote: > You might be right that the best way to do dynamic configuration is to > have a tool from a third-party (or created in house) that does monitoring > of the backend servers and edits the config file itself and reloads haproxy. > > I just don't want the hassle of finding such tools or writing my own. > Maybe haproxy could contain such a tool that is separate from haproxy but > maintained, tested, and delivered with haproxy. I have to admit that I > haven't researched any of the tools you use. I should do that, but I > always worry about creating a new dependency on a new tool since these > tools are usually available for free and could lose support and maintenance > at any time. > > HAProxy already has some support for dynamic configuration in the health > checks that mark down/up a server depending on the result of the health > check. I figure it is relatively simple to build configuration checks on > top of the health checks since most of the hard work has already been done > for health checks. > > On Jan 9, 2013, at 5:34 PM, Zachary Stern <z...@enternewmedia.com> wrote: > > Right, and my point is that you can make it dynamic without changing the > way haproxy itself works. What your asking for seems like making haproxy > itself overcomplicated, especially for people with simple deployments. But > hey, maybe I'm 100% wrong. In fact, let's operate on that assumption. > > > On Wed, Jan 9, 2013 at 5:26 PM, Kevin Heatwole <ke...@heatwoles.us> wrote: > >> I guess I wasn't clear again. I'm not talking about "editing" the >> configuration file and reloading HAProxy. >> >> My suggestion is simply to implement a dynamic interface to the backend >> servers so they can change the current behavior of the HAProxy instance >> (especially in a load balanced HAProxy backend). >> >> I'll leave it to the developers to figure out what can be dynamically >> changed and if adding a server to a backend is too complex, then that won't >> be part of the interface. >> >> On Jan 9, 2013, at 5:18 PM, Zachary Stern <z...@enternewmedia.com> wrote: >> >> I understood completely KT. It's perfectly possible to add new lines to >> the haproxy config dynamically and automatically using things like puppet. >> >> E.g. my iptables configurations are dyanmically generated as I spin up >> new servers, using puppet and the rackspace API. You could do something >> similar, regardless of cloud or not. >> >> When I spin up a new server, it's connected to puppet, tagged as a >> certain kind of server, and dynamically added as a backend to haproxy if >> appropriate. >> >> >> On Wed, Jan 9, 2013 at 5:16 PM, KT Walrus <ke...@my.walr.us> wrote: >> >>> I think you might have misunderstood. By "adding new server", I mean to >>> add it as a server in HAProxy configuration. That is, the effect is to add >>> the "server" line for the new server into the config file. This has >>> nothing to do with launching the server in the cloud. It is the reverse of >>> marking a server DOWN, except that the server being marked UP was not >>> originally included in the list of servers for the HAProxy backend. >>> >>> On Jan 9, 2013, at 4:21 PM, Zachary Stern <z...@enternewmedia.com> wrote: >>> >>> >>> >>> On Wed, Jan 9, 2013 at 4:13 PM, Kevin Heatwole <ke...@heatwoles.us>wrote: >>> >>>> 4. Adding new server to backend by having configuration check return >>>> new server configuration. >>>> >>> >>> I don't know about the other features, but this one I think violates the >>> UNIX philosophy of "do one thing and do it well". There are already plenty >>> of tools you can use to achieve this with HAproxy, like puppet or chef, and >>> things like the ruby fog gem for cloud provisioning, etc. >>> >>> >>> -- >>> >>> zachary alex stern I systems architect >>> >>> o: 212.363.1654 x106 | f: 212.202.6488 | z...@enternewmedia.com >>> >>> 60-62 e. 11th street, 4th floor | new york, ny | 10003 >>> >>> www.enternewmedia.com >>> >>> >>> >> >> >> -- >> >> zachary alex stern I systems architect >> >> o: 212.363.1654 x106 | f: 212.202.6488 | z...@enternewmedia.com >> >> 60-62 e. 11th street, 4th floor | new york, ny | 10003 >> >> www.enternewmedia.com >> >> >> > > > -- > > zachary alex stern I systems architect > > o: 212.363.1654 x106 | f: 212.202.6488 | z...@enternewmedia.com > > 60-62 e. 11th street, 4th floor | new york, ny | 10003 > > www.enternewmedia.com > > >
