first update based on feedback from Dridi Hi,
https://github.com/varnishcache/varnish-cache/wiki/Varnish-Improvement-Proposals : "The VIP procedure starts with a discussions on varnish-dev" I had skipped this bit for previous suggestions, but this time I want to get it right. I'd like to propose the following: # Synopsis Add support for calling vcl subs on the response of backend probes. # Why? Add a way to manipulate backends not just on the basis of a binary health check result, but optionally also on the basis of other information returned by the backend with the probe response. One example would be to dynamically change the weight of backends based on a load metric returned with the probe response, which will also require vmod_directors to support changing the weight dynamically. # How? * Add VCC support to register VCL subs with probes * Add a default vcl_probe_response sub to the builtin.vcl which implements the current behavior. Probes without an explicit response sub definition will use vcl_probe_response * in probe response vcl context, make the following objects available - analogous to beresp - beresp.backend - beresp.http.* - beresp.proto - beresp.status - beresp.reason - later? - beresp.body By design, all access should be read-only, but we might want to have all but .backend writable for practical reasons (writes having no effect other than being visible in the sub probe_resp) - probe.* attributes of the probe (read-only) - probe.name - probe.expected_response - probe.timeout - probe.interval - probe.initial - probe.window - probe.threshold * a probe response vcl sub may return with the following ok fail * The default vcl_probe_response: sub vcl_probe_response { if (beresp.proto ~ "^HTTP/\d+\.\d+$" && beresp.status == probe.expected_response) { return (fail); } return (ok); } this matches the existing implementation, we might want to change the first condition to beresp.proto ~ "^HTTP/1\.[01]$" once this is in place * Toy example for the use case mentioned above (needs more changes) sub probe_weight { if (beresp.http.X-Load ~ "^\d+\.\d+$") { my_rr.set_weight(beresp.backend, 1 / std.real(req.http.X-Load, 1.0)); } } _______________________________________________ varnish-dev mailing list varnish-dev@varnish-cache.org https://www.varnish-cache.org/lists/mailman/listinfo/varnish-dev