fix(server): allow disabling periodic idle vNPU cleanup to avoid premature reclamation

[dartagnanli]

What & Why

Issue #86 reports that the periodic idle vNPU cleanup goroutine (startPeriodicCheckIdleVNPUs) destroys vNPUs based solely on IsContainerUsed == 0. Because a vNPU allocated to a Pod that is already Running but whose container has not yet started using the NPU also reports IsContainerUsed == 0, the cleanup can reclaim the vNPU too early — breaking workloads (e.g. npu-smi info fails inside the container shortly after the Pod starts).

#86 is framed as a discussion and lists several more thorough directions (combining IsContainerUsed with Pod allocation state, adding a protection window, or a Pod-referenced rule like mind-cluster's DestroyNotUsedVNPU). Those require deeper changes to the cleanup policy.

This PR takes a smaller, complementary step: give operators a switch to disable the periodic cleanup goroutine so the premature-reclamation symptom stops on affected nodes without waiting for the larger redesign.

Changes

• New bool flag --enable_periodic_idle_vnpu_cleanup (default false). When false, Start() does not launch the periodic startPeriodicCheckIdleVNPUs goroutine.
• The one-shot CleanupIdleVNPUs() on plugin restart (cmd/main.go) is intentionally left unconditional and unchanged — it is a separate entry point. The flag name (enable_periodic_...) and its help text make this boundary explicit to avoid the "total cleanup switch" ambiguity.
• Wiring threaded through NewPluginServer.

Scope note

This is a mitigation, not a full resolution of #86's cleanup-policy discussion. The flag defaults to false (periodic cleanup disabled) to stop the premature-reclamation symptom by default; setting it to true restores the previous behavior. Reviewers may prefer a different default — easy to adjust.

Testing

• go build ./internal/server/... ./cmd/... ✅
• go vet ./internal/server/... ./cmd/... ✅
• go test ./internal/server/ — 109 passed, consistent with baseline (ran 3×)

Modernizations (in the touched files)

While editing these files I also applied the Go modernization lints the editor flagged. All behavior-preserving; happy to split into a separate PR if preferred:

• interface{} → any
• wg.Add(1) + go func(){ defer Done() } → wg.Go(...)
• for i := 0; i < n; i++ → for i := range n
• reverse index loop → slices.Backward

Refs #86

Summary by CodeRabbit

• New Features

  • Added an option to enable periodic cleanup of idle vNPU resources.
  • Cleanup is disabled by default and can be activated through the CLI flag.

• Bug Fixes

  • Improved server goroutine lifecycle management for more reliable startup and shutdown behavior.

• Tests

  • Updated server tests to cover the new cleanup configuration and restart behavior.

[hami-robot]

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: dd1d77fe-1d4f-4824-ab9e-432ceefbae6a

📥 Commits

Reviewing files that changed from the base of the PR and between 34bc10b and 0243445.

📒 Files selected for processing (4)

• cmd/main.go
• internal/server/register.go
• internal/server/server.go
• internal/server/server_test.go

📝 Walkthrough

Walkthrough

The CLI adds a flag for periodic idle vNPU cleanup. PluginServer accepts and applies the flag, updates stop-channel typing, and uses WaitGroup.Go for goroutine startup. Registration and server tests are updated accordingly.

Changes

Server cleanup lifecycle

Layer / File(s)	Summary
Cleanup configuration and server contract cmd/main.go, internal/server/server.go	The CLI flag is passed into NewPluginServer; the server stores it, conditionally resets and exposes stopCh, and updates related types to any.
Runtime goroutine lifecycle internal/server/server.go, internal/server/register.go	Periodic cleanup and gRPC serving use ps.wg.Go, while watchAndRegister no longer performs its own WaitGroup.Done; device construction uses for i := range vCount.
Server test alignment internal/server/server_test.go	Tests adopt the constructor and channel changes, update logger variadics to any, modernize cleanup and loop syntax, and enable periodic cleanup in restart setup.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant CLI
  participant PluginServer
  participant Cleanup
  participant GRPCServer
  CLI->>PluginServer: pass cleanup flag to NewPluginServer
  PluginServer->>PluginServer: Start with ps.wg.Go
  PluginServer->>Cleanup: start periodic cleanup when enabled
  PluginServer->>GRPCServer: start serving through ps.wg.Go
  GRPCServer-->>PluginServer: stop or restart serving

Loading

Possibly related PRs

• Project-HAMi/ascend-device-plugin#95: Related changes to server goroutine and WaitGroup lifecycle handling.

Suggested labels: enhancement

Suggested reviewers: dsfans2014, ashergaga

Poem

I’m a rabbit with cleanup to do,
Idle vNPUs get swept anew.
Goroutines hop in a managed line,
Stop channels now type just fine.
Tests thump paws and restart bright—
All servers burrow through the night.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: making periodic idle vNPU cleanup optional to prevent premature reclamation.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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