This refactors the initial approach in PR #7281, replacing the UsagePool
with a dedicated package-level sync.Map and atomic.Int64 to track
in-flight requests without global lock contention.
It also introduces a lookup map in the admin API to fix a potential
O(n^2) iteration over upstreams, ensuring that draining upstreams
are correctly exposed across config reloads without leaking memory.
Co-authored-by: Y.Horie <u5.horie@gmail.com>
reverseproxy: optimize in-flight tracking and admin API
- Replaced sync.RWMutex with sync.Map and atomic.Int64 to avoid lock contention under high RPS.
- Introduced a lookup map in the admin API to fix a potential O(n^2) iteration over upstreams.
In v2.5.0, upstream health was fixed such that whether an upstream is
considered healthy or not is mostly up to each individual handler's
config. Since "healthy" is an opinion, it is not a global value.
I unintentionally left in the "healthy" field in the API endpoint for
checking upstreams, and it is now misleading (see #4792).
However, num_requests and fails remains, so health can be determined by
the API client, rather than having it be opaquely (and unhelpfully)
determined for the client.
If we do restore this value later on, it'd need to be replicated once
per reverse_proxy handler according to their individual configs.
* 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>
