89 lines
2.7 KiB
Markdown
89 lines
2.7 KiB
Markdown
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# API-AI-R01: resolveSnapshot 并发竞争
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## 基本信息
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| 字段 | 值 |
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|------|-----|
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| Issue ID | API-AI-R01 |
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| 类型 | Non-blocking / 优化 |
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| 仓库 | api-server |
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| 关联 Issue | API-AI-016 (Snapshot Builder) |
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| 发现日期 | 2026-06-17 |
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| 优先级 | P2 |
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## 问题描述
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`runtime-internal.service.ts` 中的 `resolveSnapshot()` 存在并发竞态窗口。
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### 场景
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两个 Runtime 实例同时对同一个 job 调用 `getSnapshot()`，且 job 当前没有有效 snapshot（未生成或已过期）：
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```
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时间线 →
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实例 A 实例 B
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│ │
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├─ resolveSnapshot(job) │
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│ snapshotId=null → 进 else │
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│ ├─ resolveSnapshot(job)
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│ │ snapshotId=null → 进 else
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│ │
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├─ buildSnapshot() → snap-A │
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│ ├─ buildSnapshot() → snap-B
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│ │
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├─ job.update(snapshotId=A) │
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│ ├─ job.update(snapshotId=B) ← 覆盖 A
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```
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### 后果
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1. 数据库产生 snap-A 孤儿行（无 job 引用）
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2. 浪费一次全量聚合查询（buildSnapshot）
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3. snap-A 在 24h TTL 后自动过期清理
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### 为什么当前影响可接受
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- 不会丢数据或返回错误
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- snapshot 构建是幂等的，两份结果一致性高
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- 触发条件苛刻：两个 Runtime 实例需同时 poll 到同一个 job（poll 时有 lock 机制大幅降低概率）
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- 即使发生，额外开销仅为一次聚合查询
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## 建议修复方案
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方案：对 job 行加悲观锁后再判断 snapshot 状态。
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```typescript
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// resolveSnapshot 改为：
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private async resolveSnapshot(job) {
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// SELECT ... FOR UPDATE 锁住 job 行
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const locked = await this.prisma.aiRuntimeJob.findUnique({
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where: { id: job.id },
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// Prisma 不直接支持 FOR UPDATE，需用 $queryRaw
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});
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if (locked.snapshotId) {
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const existing = await this.prisma.learningAnalysisSnapshot.findUnique({
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where: { id: locked.snapshotId },
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});
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if (existing && (!existing.expiresAt || new Date(existing.expiresAt) >= new Date())) {
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return existing;
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}
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}
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const snapshot = await this.snapshotBuilder.buildSnapshot(...);
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await this.prisma.aiRuntimeJob.update({
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where: { id: job.id },
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data: { snapshotId: snapshot.id },
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});
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return snapshot;
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}
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```
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或者使用 `$transaction` 包裹读-判断-写逻辑，依赖数据库隔离级别保护。
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## 相关文件
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- `src/modules/ai-runtime/internal/runtime-internal.service.ts:resolveSnapshot()`
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- `src/modules/ai-runtime/snapshot-builder.service.ts:buildSnapshot()`
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