[architect] tech-debt: extract pkg/api/gpu_utilization_worker.go (413 LOC background worker) to its own package

[hivecommons-hive]

Architecture Finding

Type: tech-debt / package boundary (background worker in HTTP-wiring package)
Affected area: pkg/api/gpu_utilization_worker.go (413 LOC) + pkg/api/gpu_utilization_worker_test.go (484 LOC)

pkg/api/ is the HTTP surface package — routing, middleware, server startup, and route-group wiring. Everything else in it names its role (server.go, routes_*.go, route_group_*.go, middleware_setup.go, startup.go, buildinfo.go, config.go). The single outlier is gpu_utilization_worker.go, a self-contained periodic background worker with its own goroutine, Start()/Stop(), DCGM scraping, snapshot retention/cleanup, and threshold-alert emission.

Concrete evidence that it does not belong in pkg/api:

• Zero HTTP surface. The file exposes no http.Handler, no route registration, and no middleware — only NewGPUUtilizationWorker, Start, Stop, collectUtilization, scrapeDCGMPerCluster, collectForReservation, and cleanupOldSnapshots (7 functions total).
• Only two intra-package callers. pkg/api/server.go:272 constructs it (server.background.gpuUtilWorker = NewGPUUtilizationWorker(...)) and pkg/api/server_runtime.go:39 types the field. No other file in pkg/api touches it.
• Its own dependency graph is broader than pkg/api's. It imports pkg/gpu, pkg/k8s, pkg/models, pkg/notifications, pkg/store, pkg/safego, and pkg/api/metrics. Of those, only pkg/api/metrics is in-package; the other six are cross-cutting domains a worker naturally reaches, but a routing file should not.
• Pattern precedent already exists in this repo. The identical shape in pkg/agent was resolved by extraction: PredictionWorker, InsightWorker, DeviceTracker, and MetricsHistory were carved out of pkg/agent/*.go into pkg/agent/workers/ ([architect] refactor: extract background workers to pkg/agent/workers #18271, bead 0075a94d-1ec). The GPU worker is the mirror-image case in pkg/api, with the same size class (413 LOC production + 484 LOC tests, comparable to workers.PredictionWorker).
• Header comment on the sibling pkg/gpu/scraper.go explicitly warns about direction: "extracted from pkg/agent to break the pkg/api → pkg/agent import dependency ([architect] pkg/api directly imports pkg/agent — violates binary independence, extract shared utilities #17131, [architect] Extract DCGM types from pkg/agent to pkg/gpu #17640)". Keeping a worker under pkg/api risks re-introducing the same directional coupling the prior extraction was designed to prevent.

Impact

• Test-package confusion. Any change to pkg/api/server.go or route wiring re-triggers pkg/api/gpu_utilization_worker_test.go (484 LOC, DCGM scrape mocks and 90-day retention scenarios) even when nothing about the worker changed, because Go's test unit is the package.
• Blast-radius for pkg/api compile errors. Any breakage in the worker's dependency chain (pkg/gpu, pkg/notifications, pkg/store) breaks the whole HTTP package's build, blocking route-wiring iteration.
• Discovery friction. New contributors looking for periodic-worker patterns grep pkg/agent/workers/ and pkg/gpu/, not pkg/api/. The precedent set by the prior extraction is silently violated by this one file.
• pkg/api/metrics back-reference is the only blocker to a cleaner move to pkg/gpu/. If the metrics counter emission is dependency-injected (WorkerMetrics interface with RecordUtilization, RecordAlert methods, satisfied by pkg/api/metrics), the worker can live in pkg/gpu alongside the scraper it wraps. Without that injection, it stays trapped in pkg/api.

Recommendation

Two-step extraction, either step landable independently:

Step A — cheap move, no cycle risk (recommended first):

1. Create pkg/api/gpuworker/ package.
2. Move pkg/api/gpu_utilization_worker.go → pkg/api/gpuworker/worker.go, renaming the exported types from GPUUtilizationWorker/NewGPUUtilizationWorker to gpuworker.Worker/gpuworker.New.
3. Move pkg/api/gpu_utilization_worker_test.go → pkg/api/gpuworker/worker_test.go (adjust package and any unexported-symbol accesses).
4. Update pkg/api/server.go:272 and pkg/api/server_runtime.go:39 to use the new package name.
5. This mirrors the pkg/agent/workers extraction (#18271) exactly and does not touch dependency direction.

Step B — cross-package move (do only after Step A stabilises):

1. Introduce a Metrics interface in pkg/api/gpuworker covering the two consolemetrics calls the worker makes (grep consolemetrics\. inside the file to enumerate).
2. Move pkg/api/gpuworker/ → pkg/gpu/utilworker/ with the interface constructor-injected from pkg/api/server.go (which retains the concrete consolemetrics import). This preserves the pkg/api → pkg/gpu direction the pkg/gpu/scraper.go header comment mandates.

No workflow (.github/workflows/) changes required for either step — both stay inside pkg/.

Related historical extractions (for reviewer context):

• #18271 / bead 0075a94d-1ec: pkg/agent/workers (PredictionWorker, InsightWorker, DeviceTracker, MetricsHistory)
• #18310 / bead 924f0d4a-91e: pkg/agent/tokentracker
• #18125 / bead 0f137940-e25: pkg/agent/updater
• #17131/#17640: pkg/gpu split from pkg/agent to break pkg/api → pkg/agent direction

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Filed by architect agent (ACMM L6 — full mode)

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[hivecommons-hive]

A merged PR referenced this issue without closing it. Carrying the remainder back here so the issue timeline shows what is still open.

• refactor: extract pkg/api/gpu_utilization_worker.go to pkg/api/gpuworker [architect] #23736 — refactor: extract pkg/api/gpu_utilization_worker.go to pkg/api/gpuworker [architect] (refactor: extract pkg/api/gpu_utilization_worker.go to pkg/api/gpuworker [architect] #23736) — needs human

Remainder from the PR body:

Step B — moving pkg/api/gpuworker further to pkg/gpu with a Metrics interface — remains open; also the underlying ai.SetClusterContextProviders init-time coupling deserves its own follow-up

This comment is edited in place by the task-list sweep on every cycle; it is not duplicated.

[hivecommons-hive]

Verified against main (commit 47b5c85): Step A is already complete via PR #23736.

• pkg/api/gpuworker/worker.go and pkg/api/gpuworker/worker_test.go exist (package gpuworker, types Worker/New).
• pkg/api/gpu_utilization_worker.go and its test no longer exist in pkg/api/.
• pkg/api/server.go:273 uses gpuworker.New(db, k8sClient, notificationService).
• pkg/api/server_runtime.go:40 field type is *gpuworker.Worker.
• Repo-wide grep for GPUUtilizationWorker/NewGPUUtilizationWorker returns no matches.

No code changes needed; closing as already resolved. No PR opened.

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