* reverseproxy: Improve hashing LB policies with HRW
Previously, if a list of upstreams changed, hash-based LB policies
would be greatly affected because the hash relied on the position of
upstreams in the pool. Highest Random Weight or "rendezvous" hashing
is apparently robust to pool changes. It runs in O(n) instead of
O(log n), but n is very small usually.
* Fix bug and update tests
* reverseproxy: Begin refactor to enable dynamic upstreams
Streamed here: https://www.youtube.com/watch?v=hj7yzXb11jU
* Implement SRV and A/AAA upstream sources
Also get upstreams at every retry loop iteration instead of just once
before the loop. See #4442.
* Minor tweaks from review
* Limit size of upstreams caches
* Add doc notes deprecating LookupSRV
* Provision dynamic upstreams
Still WIP, preparing to preserve health checker functionality
* Rejigger health checks
Move active health check results into handler-specific Upstreams.
Improve documentation regarding health checks and upstreams.
* Deprecation notice
* Add Caddyfile support, use `caddy.Duration`
* Interface guards
* Implement custom resolvers, add resolvers to http transport Caddyfile
* SRV: fix Caddyfile `name` inline arg, remove proto condition
* Use pointer receiver
* Add debug logs
Co-authored-by: Francis Lavoie <lavofr@gmail.com>
* caddyhttp: reverseproxy: fix hash selection policy
Fixes: #4135
Test: go test './...' -count=1
* caddyhttp: reverseproxy: add test to catch #4135
If you revert the last commit, the test will fail.