On Sat, Oct 27, 2018 at 01:52:29PM +0200, Aleksandar Lazic wrote: > > Right now, if you want to use load feedback for weights, you either need > > something entirely out-of-band from the servers back to HAProxy, or you > > have to use the agent-check option and run a separate health agent. > > With that you mean "external-check command" ? > > https://cbonte.github.io/haproxy-dconv/1.8/configuration.html#external-check%20command No, I mean 'agent-check' per https://cbonte.github.io/haproxy-dconv/1.8/configuration.html#5.2-agent-check
This is an agent that runs on the realserver, not the load balancer. ... > > I would like to propose a new http-agent-check option, with two usage > > modes. > > 1. health-check mode: this connects like the existing agent-check, but > > sends does HTTP request & response rather than pure TCP. > > > > 2. inline mode: if the server has best-case knowledge about it's status, > > and HTTP headers are used for the feedback information, then it > > should be possible to include the feedback in an HTTP response header > > as part of normal queries. The header processing would detect & feed > > the data into the health system during normal traffic. > > Interesting Ideas. > Are there any LB's out there which already uses this concept? I haven't looked specifically, but I am aware of a lot of other dynamic-realserver weight work (mostly in the keepalived/ipvs world, like feedbackd and lvs-kiss from the early 2000's). The inline mode is probably deserving of seperate work, I think it might be possible to implement it with the existing Lua codebase. > > Question: where & how should the feedback information be encoded in the > > response? > > 1. HTTP payload > > 2. Single HTTP header > > 3. Multiple HTTP headers > > I would like to have it in the one header per value 'Server-State-*' as the X- > Prefix is Deprecated. > > https://tools.ietf.org/html/rfc6648 > Deprecating the "X-" Prefix and Similar Constructs in Application Protocols > > for example: > Server-State-Load > Server-State-Users > Server-State-Health > Server-State-... Multiple headers easier to write new parsers for I agree, but supporting the other variants might be worthwhile. I'm thinking to maybe implement my lua-check first, then write a simple HTTP checker within Lua. -- Robin Hugh Johnson E-Mail : robb...@orbis-terrarum.net Home Page : http://www.orbis-terrarum.net/?l=people.robbat2 GnuPG FP : 11ACBA4F 4778E3F6 E4EDF38E B27B944E 34884E85
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