feat!: judge idle reservations by the reserved device, not process identity

[KinjiKawaguchi]

Why

Running a workload inside Docker made the idle-reservation watch nag its owner repeatedly, because usage attribution rested on a single chain — PID → real UID → getent → username → owner — that breaks under containers, user namespaces, and shared accounts. The breakage was swallowed silently: the reporter dropped unresolvable processes, and the judgement read "no process attributable to the owner" as "absent".

Closes #160

What

• Judge idleness device-first. judge_reservation_activity now reads what happens on the reserved device — utilization and the presence of any usage — without asking whose processes they are. A reservation already binds the device to the person responsible; matching identities stays with unauthorized-usage detection. The OS-username link is no longer a precondition for judging, so owners without one now receive idle notices too.
• Report unattributed processes. gpu-usage-reporter reports processes whose UID cannot be resolved as unattributed entries (with the raw UID) instead of dropping them, and the shared-file observer carries them into the snapshot. The field is additive and optional in both directions: old reports keep parsing, old servers ignore the new field.
• Quiet handling for unknown DM recipients. An owner with no Slack link used to surface as a SendFailure on every poll. NotificationError::RecipientUnknown now tells "we do not know where to send this" apart from "sending broke"; idle detection counts it quietly and backs off for the usual silence window.
• Guides updated accordingly (judgement wording, report schema, verification steps).

Behavior changes

• Someone else computing on a reserved GPU no longer triggers a misleading "not in use" notice to the owner (the squatter is still handled by the unauthorized-usage flow).
• Owners who never linked an OS username were previously never notified; they now are.
• "Held without computing" covers any allocation on the reserved device, not only the owner's own processes.

How

Breaking for the library API — the next release becomes 2.0.0: DetectIdleReservationsUseCase loses its IdentityLinkRepository type parameter and constructor argument (its judgement also becomes synchronous), judge_reservation_activity drops owner_identities, GpuUsageReport gains a required field, and NotificationError gains a variant. Riding the same major: all public error enums are now #[non_exhaustive], so future failure kinds ship as minor releases; external matches need a wildcard arm.

Nothing operational breaks: no env var changes, the report JSON schema is additive, and reporters and the server can be updated in either order. ObservationSnapshot gains unattributed_usages, kept as a parallel collection so the reconcile flow is untouched.

🤖 Generated with Claude Code

[Copilot]

🔵 Needs a closer look

judge_reservation_activity can still misclassify a reservation as Absent when utilization indicates computing but no process entries are present (e.g., short-lived work between utilization sampling and process snapshot), which risks reintroducing false idle notices.

Pull request overview

This PR updates idle-reservation detection to judge “in use / held / absent” based on what is happening on the reserved GPU devices (utilization + any observed usage), rather than attributing processes to the reservation owner (which breaks under containers / namespaces). It also extends the GPU usage report schema to carry “unattributed” usages (UIDs that cannot be resolved to OS usernames) and refines notification error handling so unknown DM recipients don’t count as repeated delivery failures.

Changes:

• Make reservation activity judgement device-first and include unattributed usages in snapshots and judgement.
• Extend gpu-usage-reporter + shared-file observer schema with unattributed usage entries to avoid silently dropping unresolvable UIDs.
• Introduce NotificationError::RecipientUnknown and adjust idle-notice handling/backoff + docs accordingly.

File summaries

File	Description
src/lib.rs	Re-exports the new UnattributedUsageEntry in the public prelude.
src/infrastructure/slack_direct_message.rs	Classifies missing IdentityLink/Slack link as RecipientUnknown instead of SendFailure.
src/infrastructure/resource_usage_observer/shared_file.rs	Adds unattributed parsing/serialization and threads unattributed usages into ObservationSnapshot.
src/infrastructure/resource_usage_observer/mod.rs	Re-exports UnattributedUsageEntry from the shared-file observer module.
src/infrastructure/idle_reservation_notifier/slack.rs	Updates idle-notice wording to be owner-agnostic (“利用を確認できていません”).
src/infrastructure/idle_reservation_notifier/mock.rs	Adds mock behavior for RecipientUnknown to test quiet/backoff behavior.
src/domain/services/resource_usage/reservation_activity.rs	Changes reservation activity judgement to be identity-agnostic and include unattributed usages.
src/domain/ports/resource_usage_observer.rs	Introduces UnattributedUsage + ObservationSnapshot::with_unattributed_usages/accessor.
src/domain/ports/notifier.rs	Adds NotificationError::RecipientUnknown and Display formatting.
src/domain/ports/mod.rs	Re-exports UnattributedUsage through the domain ports module.
src/domain/ports/idle_reservation_notifier.rs	Updates idle evidence semantics to be about “any usage” on reserved GPUs.
src/bin/lab-resource-manager.rs	Updates use case wiring due to DetectIdleReservationsUseCase signature change.
src/bin/gpu-usage-reporter.rs	Emits unattributed entries (device_number, uid, started_at, used_memory_mib) instead of dropping unknown UIDs.
src/application/usecases/detect_idle_reservations.rs	Removes identity-link dependency for judging; treats RecipientUnknown quietly with normal silence backoff.
src/application/usecases/detect_idle_reservations_tests.rs	Updates tests for device-first judgement and adds unattributed + recipient-unknown scenarios.
docs/USER_GUIDE.md	Documents that containerized compute still counts as “in use” regardless of process identity.
docs/USER_GUIDE_ja.md	Japanese guide updates matching the device-first judgement behavior.
docs/ADMIN_GUIDE.md	Documents unattributed schema and updates idle threshold semantics/verification steps.
docs/ADMIN_GUIDE_ja.md	Japanese admin guide updates for unattributed schema and device-first judgement behavior.

Review details

Suppressed comments (2)

src/domain/services/resource_usage/reservation_activity.rs:111

• judge_reservation_activity returns Absent when no process-based usage is observed, even if GPU activity shows the reserved device was computing during the sampling window. Because gpu-usage-reporter samples utilization over a window and only then snapshots processes, short-lived or just-finished workloads can legitimately produce devices[].peak_utilization_percent without any processes/unattributed entries, and this path would misclassify them as absent and potentially trigger an idle notice.

    let occupied = occupied_gpus(reserved, snapshot);

    if occupied.is_empty() {
        return ReservationActivity::Absent;
    }

src/bin/gpu-usage-reporter.rs:382

• resolve_username is invoked once per observed process, which can spawn many getent subprocesses when multiple processes share the same UID. Caching UID→username (including negative lookups) within the process would avoid redundant getent calls and reduce runtime overhead.

/// UIDをこのホストのOSユーザー名に解決する
///
/// コンテナ内のUIDやuser namespaceでずらされたUIDは、このホストのアカウントに
/// 対応せず解決できない。それは利用がないことではなく、持ち主が分からないことを意味する。
fn resolve_username(uid: u32) -> Option<String> {
    let output = Command::new("getent")
        .args(["passwd", &uid.to_string()])
        .output()
        .ok()?;
    if !output.status.success() {
        return None;
    }

    let stdout = String::from_utf8(output.stdout).ok()?;
    stdout.split(':').next().map(str::to_string)
}

• Files reviewed: 19/19 changed files
• Comments generated: 0
• Review effort level: Lite

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[Copilot]

Copilot review overview

🔵 Needs a closer look

judge_reservation_activity can still classify a reservation as Absent even when utilization sampling indicates computation (utilization-only evidence is ignored when no process entries are present).

Review effort: Lite
Findings: None

[Copilot]

Copilot review overview

🔵 Needs a closer look

It introduces breaking API changes and modifies core idle/notification behavior across multiple layers (reporter, observer, domain logic, and docs), warranting final human review.

Review effort: Lite
Findings: None