Willy. Yes. That sounds good to me.
Thanks. And have a nice Christmas... On 24 December 2012 09:23, Willy Tarreau <w...@1wt.eu> wrote: > Hi Malcolm, > > On Mon, Dec 24, 2012 at 09:06:25AM +0000, Malcolm Turnbull wrote: >> Willy / Simon, >> >> I'm very happy to add a down option, my original thought was that you >> would use the standard health checks as well as the dynamic agent for >> changing the weight. > > That's what I thought I initially understood from our discussion a few > months ago but then your post of the specs last week slightly confused > me as I understood you needed this as a dedicated check. I think it was > the same for Simon. > >> As you may for example want a specific HAproxy SMTP health check + use >> the dynamic weighting agent. > > Exactly. But then we have two options : > - retrieve the information from the checked port (easy for HTTP or TCP) > - retrieve the information from a dedicated port => this involves a > second task to do this, with its own check intervals. > > The latter doesn't seem stupid at all, quite the opposite in fact, but > it will require more settings on the server line. However it comes with > a benefit, it is that when the agent returns "disable", checks are > disabled on the real port, but then we could have the agent continue to > be checked and later return a valid result again. > >> I'm not sure if that would cause some coding issues if the health >> checks say 'Down' and the agent says 50%? (I would assume haproxy >> health checks take priority?) > > Status and weights are orthogonal. The real check should have precedence. > >> Or if the agent says Down but the HAProxy health check says up? > > I think it should be ANDed. This could help provide a first implementation > of multi-port checks after all. > >> I've certainly happy for Down to be added as an option with a >> description string. >> Also I'm assuming that later (the dynamic agent) could easily be >> extended to an http style get check rather than TCP (lb-agent-chk) if >> users prefer to write an HTTP server application to integrate with it >> (Kemp and Barracuda support this method). > > That's what I'm commonly observing too. Even right now, there are a lot > of users who use httpchk for services that are not HTTP at all, but they > have a very simple agent responding to checks. > > So now we have to decide what to do. I think Simon's code already provides > some useful features (assuming we support "down"). It should probably be > extended later to support combined checks. > > In my opinion, this could be done in three steps : > > 1) we merge Simon's work with the "option lb-agent-chk" directive which > *replaces* the health check method with this one ; > > 2) we implement "agent-port" and "agent-interval" on the server lines to > automatically enable the agent to be run on another port even when a > different check is running ; > > 3) we implement "http-check agent-hdr <name>" to retrieve the agent string > from an HTTP header for HTTP checks ; > > That way we always support exactly the same syntax but can retrieve the > required information at different places depending on the checks. Does > that sound good to you ? > > Best regards, > Willy > -- Regards, Malcolm Turnbull. Loadbalancer.org Ltd. Phone: +44 (0)870 443 8779 http://www.loadbalancer.org/
