baozaotumao
39fe248f9f
- 新增 .claude/skills/new-project/SKILL.md（标准 skill 格式） - install-skill.sh 安装时组装 SKILL.md + verify.sh，单一源无重复 - verify.sh 改用索引数组替代 declare -A，兼容 macOS bash 3.2 - log_pass/log_skip 显式 return 0，避免 set -e 下非 verbose 误退出 - README 改为 skill 优先；补全 copier.yml/scripts/template 入库
48 lines
2.0 KiB
Markdown
48 lines
2.0 KiB
Markdown
---
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paths: ["backend/**"]
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---
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# backend-concurrency
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Backend 并发模型：WebSocket 双向转发的 Task 管理 + SQLite 并发处理。
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Backend 是纯异步 I/O 代理，无 CPU 密集工作，无需进程池。关注点在两处：双向转发的任务管理、SQLite 并发。
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## 1. WebSocket 双向转发
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每个连接 = 两个 Task（上行 / 下行），并联运行；任一侧断开必须取消另一侧，避免 Task 泄漏：
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```python
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@router.websocket("/ws/{session_id}")
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async def ws_proxy(ws: WebSocket, session_id: str, repo: SessionRepository = Depends(get_session_repo)):
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await ws.accept()
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await session_service.get_or_create(repo, session_id)
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checkpoint = await session_service.load_checkpoint(repo, session_id)
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async with agent_client.connect(session_id, checkpoint=checkpoint) as agent_ws:
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to_agent = asyncio.create_task(forward_to_agent(ws, agent_ws))
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to_browser = asyncio.create_task(forward_to_browser(agent_ws, ws, repo)) # 转发同时写 checkpoint
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done, pending = await asyncio.wait(
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{to_agent, to_browser}, return_when=asyncio.FIRST_COMPLETED
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)
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for task in pending: # 一侧结束，取消另一侧
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task.cancel()
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```
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## 2. SQLite 并发
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SQLite 默认串行写，并发下易触发 `database is locked`。引擎连接时必须开 WAL + busy_timeout：
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```python
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# db/base.py —— connect 时执行
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@event.listens_for(engine.sync_engine, "connect")
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def set_sqlite_pragma(dbapi_conn, _):
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cursor = dbapi_conn.cursor()
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cursor.execute("PRAGMA journal_mode=WAL") # 读写不互斥
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cursor.execute("PRAGMA busy_timeout=5000") # 锁等待 5s 而非立即报错
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cursor.execute("PRAGMA foreign_keys=ON")
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cursor.close()
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```
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- 一个请求/连接一个 `AsyncSession`（`get_db` 作用域），**禁止跨 Task 共享 Session**
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- 本工作负载写入量低，WAL 足够；若未来高并发，迁移到 Postgres（仅换 `database_url` 与 driver，ORM 不变）
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