Every deploy on a hive host, the replacement opentelemetry-collector
reaches bind() while the outgoing process still holds
127.0.0.1:8888 (its self-scrape endpoint). nixpkgs sets
Restart = "always" with no RestartSec, so the unit spends its five
default attempts in under two seconds, hits start-limit-hit and stops
retrying — ~27s of telemetry blackout per deploy.
RestartSec = 5 with a 12-attempt burst over a 120s window rides the
race out instead: the blackout ends within one interval of the port
coming free, and 55s of it being held is survivable where 2s was not.
StartLimitBurst/StartLimitIntervalSec go at the systemd.services attr
level, which NixOS renders into [Unit]; under serviceConfig systemd
ignores them silently. module-eval-hive-otel asserts the placement.
The single module-eval derivation forced ~62 full nixosSystem
fixtures live at once to compute its cases list: 10.6GB peak RSS /
5m25s to evaluate, by far the dominant cost in nix flake check.
Splits it into 21 independent checks.module-eval-* derivations
(1-7 fixtures each) sharing builders/helpers via module-eval/lib.nix,
so no single derivation needs more than a handful of fixtures live
at once. A few cases spanning two clusters carry a small duplicated
fixture rather than threading shared state through lib.nix.
