Device verification of round_robin on a real 51-node pool surfaced three bugs,
all fixed here. Listed by impact.
1. sticky key 'domain' was always empty -> all traffic collapsed to one node.
The router resolves a domain destination to an IP and overwrites
metadata.Destination before a group's DialContext runs, so destination.Fqdn
is empty when the balancer builds the key. stickyComponent("domain") read
that empty Fqdn, so a single process's key was process+NUL for every site
-> one fixed slot. On device this measured 28/1/1 across a 3-node pool
(uniformity 0.27). Fix: read metadata.Domain (survives the resolve), fall
back to destination.Fqdn only for a direct dial. After: spread 0.95+.
2. living pool nodes could change slot index during a health-check, moving
sticky keys. balancePoolFirstLive compacted with a filtering append (a
transiently-dead slot shifted every later live node left); planTolerantPool
did delete(inPool, occupant) (an evicted-but-living node re-entered a later
slot, cascading); manual URLTest rebuild ran the tolerant planner even at
pool_tolerance==0. All now replace-in-slot (fixed-length copy(current), only
dead/empty slots rewritten by index; dedicated planFirstLivePool for the
tolerance==0 rebuild).
3. stickiness could not be disabled via sticky_hash: [] -- the config decoder
(badjson.UnmarshallExcludedContext) re-marshals the struct and collapses an
empty array to nil, indistinguishable from omitted, so the default always
applied. Disabling now uses the explicit sentinel sticky_hash: ["none"].
Tests: domain-from-metadata + fallback, replace-in-slot survivor/cascade/
first-live regressions (fail against pre-fix code), ["none"] disable + []
defaults + none-mixed error. All green under -race; gofmt clean.
Leadaxe
a531879e02