feat(scanner): emit excess alerts as S3 notification events (HS-04) (#6176)

* feat(scanner): emit excess alerts as S3 notification events

The excess-versions / excess-version-size / excess-folders alerts were
metrics-and-logs only; consoles and external auditors had no way to hear
them (rustfs/backlog#1868, HS-04). MinIO emits s3:ObjectManyVersions /
s3:ObjectLargeVersions / s3:PrefixManyFolders for the same conditions —
RustFS carries those as EventName::Scanner* with s3:Scanner:* wire names
that already existed unpublished.

The three alert sites now also dispatch through the standard event
pipeline (send_event via the storage_api owner facade), carrying the
actual values and thresholds in req_params and UserAgent "Scanner".
Without a cooldown a single over-threshold object would re-emit on every
~60s scan cycle, so emissions are edge-held per (kind, bucket, object)
for 24h (RUSTFS_SCANNER_ALERT_COOLDOWN_SECS, 0 = every cycle), backed by
a process-global map with a 4096-key hard cap that clears rather than
grows. Metrics and structured logs stay level-triggered every cycle;
only the notification events are held back. A restart resets the
cooldown deliberately: one re-emission per still-hot key buys back
visibility after the restarts that accompany incident response.

Tests pin the edge-hold semantics (first fires, immediate re-check held,
independent keys, cooldown expiry re-fires, zero cooldown always emits,
hard bound) in one sequential test for the process-global map, and pin
the emitted wire names against EventName's canonical string forms so a
subscribed bucket notification can never silently stop matching.
docs/operations/scanner-excess-alerts.md documents the three events,
the metric-vs-event cadence difference, and the HS-15 threshold deltas
(alert_excess_folders 65538 vs MinIO 50000 is deliberate: Proxmox
Backup Server chunk layout compatibility).

Closes rustfs/backlog#1868.

Co-Authored-By: heihutu <heihutu@gmail.com>

* docs(operations): split scanner excess alerts into English and Chinese pages

The page shipped Chinese-only; keep it as scanner-excess-alerts_zh.md and
add a faithful English translation at the original path, cross-linked at
the top of both.

Co-Authored-By: heihutu <heihutu@gmail.com>

---------

Co-authored-by: heihutu <heihutu@gmail.com>
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# Scanner Excess Alerts: Metrics, S3 Events, and Thresholds
> 中文版:[scanner-excess-alerts_zh.md](scanner-excess-alerts_zh.md)
Date: 2026-08-18 (rustfs/backlog#1868 / HS-04; includes the HS-15 threshold-delta notes)
The background scanner detects three classes of "excess" conditions while it walks buckets and surfaces them as alerts. This page documents each alert's trigger condition, the subscribable S3 event, the cooldown semantics, and the threshold differences versus MinIO — for operators debugging alerts and for event consumers wiring up subscriptions.
## The three alerts
| Alert | Trigger (per scan cycle) | Metric | S3 event (RustFS wire name) | MinIO event name |
|---|---|---|---|---|
| Excess versions | Retained versions of one object ≥ `scanner:alert_excess_versions` | `rustfs_scanner_excess_object_versions_total{bucket}` | `s3:Scanner:ManyVersions` | `s3:ObjectManyVersions` |
| Excess version size | Cumulative bytes of all versions of one object ≥ `scanner:alert_excess_version_size` | `rustfs_scanner_excess_object_version_size_total{bucket}` | `s3:Scanner:LargeVersions` | `s3:ObjectLargeVersions` |
| Excess folders | Direct subfolders of one directory > `scanner:alert_excess_folders` | `rustfs_scanner_excess_folders_total{root}` | `s3:Scanner:BigPrefix` | `s3:PrefixManyFolders` |
Subscribe like any bucket notification: configure a notification on the target bucket with the RustFS wire name above (or the `s3:Scanner:*` wildcard). Events carry `UserAgent: Scanner` as their origin marker, and `req_params` holds the observed value and the threshold (`versions` / `cumulativeSize` / `folders` / `threshold`), so consumers can judge severity directly.
## Metrics and events fire on different cadences
- **Metrics and structured logs are level-triggered**: as long as the object stays over the threshold, every scan cycle counts and logs it (default cycle ≈ 60s; see `scanner:speed`).
- **S3 events are edge-triggered with a cooldown**: the same (alert kind, bucket, object) emits at most once per cooldown window — 24 hours by default (`RUSTFS_SCANNER_ALERT_COOLDOWN_SECS`; set it to 0 to emit every cycle). When the window lapses and the object is still over the threshold, the event fires again. The cooldown table lives in process memory with a 4096-entry hard cap; on overflow it is cleared and rebuilt (worst case: one extra emission per still-hot key).
- A process restart resets the cooldown (every still-over-threshold object emits once more after a restart) — deliberately: restarts usually accompany incident response, and the re-emission buys visibility.
## Threshold defaults and the MinIO deltas (HS-15)
| Config key | ENV | RustFS default | MinIO default | Notes |
|---|---|---|---|---|
| `scanner:alert_excess_versions` | `RUSTFS_SCANNER_ALERT_EXCESS_VERSIONS` | 100 | 100 | Identical |
| `scanner:alert_excess_version_size` | `RUSTFS_SCANNER_ALERT_EXCESS_VERSION_SIZE` | 1 TiB | 1 TB | Same order of magnitude; different unit basis (TiB vs TB) |
| `scanner:alert_excess_folders` | `RUSTFS_SCANNER_ALERT_EXCESS_FOLDERS` | 65538 | 50000 | **Deliberate divergence**: 65538 tolerates the Proxmox Backup Server chunk layout (65536 chunks per directory plus the directory's own entries); MinIO's 50000 would fire continuously for PBS users. Set it to 50000 explicitly to match MinIO behavior |
All three keys accept both env and admin config (`PUT /rustfs/admin/v3/config`, `scanner` subsystem); hot updates take effect immediately.
## Why the event names are mapped
RustFS's event enum (`rustfs_s3_types::EventName::ScannerManyVersions/LargeVersions/BigPrefix`) keeps the repo's established `s3:Scanner:*` wire names (literally different from MinIO's `s3:ObjectManyVersions`; the enum comments preserve the mapping). Subscribers should use the RustFS wire names in this page. If you need MinIO-literal compatibility, map the names on the console/consumer side — do not change the published wire names.
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# Scanner 超限告警:指标、S3 事件与阈值
> English version: [scanner-excess-alerts.md](scanner-excess-alerts.md)
日期:2026-08-18rustfs/backlog#1868 / HS-04,含 HS-15 阈值差异说明)
后台 scanner 在扫描过程中检测三类"超限"状态并对外告警。本文说明每类告警的触发条件、可订阅的 S3 事件、冷却语义,以及与 MinIO 的阈值差异,供运维排障与事件消费方对接。
## 三类告警
| 告警 | 触发条件(任一扫描周期) | 指标 | S3 事件(RustFS wire 名) | MinIO 对应事件名 |
|---|---|---|---|---|
| 版本数超限 | 单对象保留版本数 ≥ `scanner:alert_excess_versions` | `rustfs_scanner_excess_object_versions_total{bucket}` | `s3:Scanner:ManyVersions` | `s3:ObjectManyVersions` |
| 版本总大小超限 | 单对象全部版本累计字节 ≥ `scanner:alert_excess_version_size` | `rustfs_scanner_excess_object_version_size_total{bucket}` | `s3:Scanner:LargeVersions` | `s3:ObjectLargeVersions` |
| 子目录数超限 | 单目录直接子目录数 > `scanner:alert_excess_folders` | `rustfs_scanner_excess_folders_total{root}` | `s3:Scanner:BigPrefix` | `s3:PrefixManyFolders` |
订阅方式与普通桶通知一致:对目标桶配置 notification,事件名填上表 RustFS wire 名(或通配 `s3:Scanner:*`)。事件以 `UserAgent: Scanner` 标记来源,`req_params` 携带实际值与阈值(`versions` / `cumulativeSize` / `folders` / `threshold`),便于消费方直接判断严重程度。
## 指标与事件的触发节奏不同
- **指标与结构化日志是电平触发**:只要对象仍在阈值之上,每个扫描周期都会计数/打日志(默认周期约 60s,见 `scanner:speed`)。
- **S3 事件是边沿触发 + 冷却**:同一 (告警类型, 桶, 对象) 在冷却窗口内只发一次,默认 24 小时(`RUSTFS_SCANNER_ALERT_COOLDOWN_SECS`,设 0 表示每周期都发)。窗口过后对象仍超限会再次发出。冷却表在进程内有 4096 条硬顶,超限清空重建(最坏情况是每个仍超限的 key 多发一次)。
- 进程重启会重置冷却(重启后每个仍超限的对象会再发一次)——这是有意为之:重启常伴随排障,重发提供可见性。
## 阈值默认值与 MinIO 差异(HS-15
| 配置键 | ENV | RustFS 默认 | MinIO 默认 | 差异说明 |
|---|---|---|---|---|
| `scanner:alert_excess_versions` | `RUSTFS_SCANNER_ALERT_EXCESS_VERSIONS` | 100 | 100 | 一致 |
| `scanner:alert_excess_version_size` | `RUSTFS_SCANNER_ALERT_EXCESS_VERSION_SIZE` | 1 TiB | 1 TB | 语义同量级,单位口径不同(TiB vs TB) |
| `scanner:alert_excess_folders` | `RUSTFS_SCANNER_ALERT_EXCESS_FOLDERS` | 65538 | 50000 | **有意差异**65538 兼容 Proxmox Backup Server 的 chunk 布局(每目录 65536 个 chunk + 目录自身条目),按 MinIO 的 50000 会对 PBS 用户持续误报。如需与 MinIO 行为一致可显式配置为 50000 |
三个键均支持 env 与 admin config`PUT /rustfs/admin/v3/config``scanner` 子系统)双通道,热更新即时生效。
## 事件名映射的由来
RustFS 的事件枚举(`rustfs_s3_types::EventName::ScannerManyVersions/LargeVersions/BigPrefix`)沿用仓库既有 wire 名 `s3:Scanner:*`(与 MinIO 的 `s3:ObjectManyVersions` 字面不同,枚举注释中保留了映射关系)。订阅方应以本文的 RustFS wire 名为准;如需 MinIO 字面兼容,请在 console/消费侧做名称映射,不要修改已发布的 wire 名。