All, We currently support strict and timed round robin for round robin DNS records and I'd like to propose adding consistent hashing based DNS selection. We're trying to replace our current ATS -> Haproxy setup with only ATS and that's been the motivation behind all of our recent HostDB improvements because we (and many others) use Haproxy simply for load balancing / host selection.
I've been hacking around with a few ideas and implementation methods but basically here is what I have so far: 1) Add a new records.config called called proxy.config.hostdb.consisent_hash of type INT which will enable / disable the feature. 2) Add a new records.config option called proxy.config.hostdb.consistent_hash_selection of type STRING, this will be how the string is assembled to produce the hash. After bouncing a few ideas around I was thinking a subset of the custom log format strings make the most sense ( https://docs.trafficserver.apache.org/en/latest/admin/event-logging-formats.en.html), so basically you would do something like: CONFIG proxy.config.hostdb.consistent_hash_selection STRING %<cqup> %<{X-Foo-Header}cqh> This would hash based on the pre-remapped request path and an incoming header called "X-Foo-Header." Reusing this existing syntax seemed to make the most sense. Additionally, because cookies are typically a good way to uniquely identify a session I'll likely add another format which will get the value of an individual cookie, is this something people would find useful? I'd really love feedback before I land the patch. Thoughts? Thanks, Brian
