浅念
106 lines
4.7 KiB
Python
106 lines
4.7 KiB
Python
"""TenantHostMiddleware——按 Host 头解析租户的纯 ASGI 中间件(Task 7)。
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为什么必须是纯 ASGI 类而不是 ``@app.middleware("http")``(前序审查实证过
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的坑): 那条路走 BaseHTTPMiddleware,只跑 http scope——WebSocket 请求会
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整个绕过租户解析落进 routes/runtime.py 的兜底,租户 A 的 WS 流量静默写进
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租户 B 的库(串库不崩溃,极难发现)。本类自己分发 http 与 websocket 两种
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scope type,两条路都先过租户解析。
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行为:
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- scope 非 http/websocket(lifespan 等)原样放行;
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- path 精确等于 ``/health`` 豁免(部署健康检查 ``curl 127.0.0.1:8018``
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/health,Host 是 IP:端口必然未知;精确匹配,``/healthxxx`` 不豁免);
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- Host 头 → ``registry.resolve_site``: 未知 → http 404 / ws close(1008);
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租户停用 → http 503 中性"服务暂停"页(不暴露租户信息)/ ws close(1013);
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- 解析成功把 tenant/site 写进 ``scope["state"]``——Request/WebSocket.state
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与 scope["state"] 共享同一 dict(setdefault 保证),routes 的 get_runtime
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即读到本中间件写入的 runtime。
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Registry 延迟取: ``add_middleware`` 实例化时 lifespan 还没跑、
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``app.state.registry`` 未挂,构造期拿不到——从 ``scope["app"].state``
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逐请求取(Starlette 在中间件栈外层保证 scope 带 app)。
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"""
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from starlette.responses import HTMLResponse, PlainTextResponse
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from starlette.types import ASGIApp, Receive, Scope, Send
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# 归一复用 registry 的私有实现——同一包内单一事实源,中间件与域名索引
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# 的建法永不漂移(resolve_site 内部也会再归一次,双保险无害)
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from app.platform.registry import (
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TenantDisabledError,
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UnknownTenantError,
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_normalize_host,
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)
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# 中性"服务暂停"页: 不暴露租户 slug/域名/停用原因(可能是欠费等敏感信息)
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PAUSE_PAGE = (
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"<!DOCTYPE html><html lang=\"zh-CN\"><head><meta charset=\"utf-8\">"
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"<title>服务暂停</title></head>"
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"<body style=\"font-family:system-ui,sans-serif;text-align:center;"
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"padding:4rem 1rem;color:#333;\">"
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"<p style=\"font-size:1.1rem;\">服务暂停维护中，请稍后再试。</p>"
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"</body></html>"
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)
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def _host_from_scope(scope: Scope) -> str:
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"""ASGI headers(小写 bytes 键值对)里的 host → str 并归一。"""
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for key, value in scope.get("headers") or []:
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if key == b"host":
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return _normalize_host(value.decode("latin-1"))
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return ""
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async def _close_ws(receive: Receive, send: Send, code: int, reason: str) -> None:
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"""以 close 代 accept 拒绝 WS(ASGI 规范序列: 先收到 websocket.connect,
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再回 websocket.close)。reason 中性,不带租户信息。
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客户端在握手期间放弃时收到的首个事件是 websocket.disconnect 而非
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connect——对端已撤,close 送达不了,直接 return。receive 本身抛异常
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(传输层断)则向上传播,由外层 ServerErrorMiddleware 记日志:拒绝路径
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无任何已建立状态可留,无需也不应再兜一层。"""
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event = await receive()
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if event["type"] == "websocket.disconnect":
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return
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await send({"type": "websocket.close", "code": code, "reason": reason})
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class TenantHostMiddleware:
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"""纯 ASGI 租户路由中间件(设计动机见模块 docstring)。"""
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def __init__(self, app: ASGIApp) -> None:
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self.app = app
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async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
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if scope["type"] not in ("http", "websocket"):
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return await self.app(scope, receive, send)
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if scope.get("path") == "/health":
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return await self.app(scope, receive, send)
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registry = getattr(scope["app"].state, "registry", None)
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if registry is None:
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raise RuntimeError(
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"app.state.registry 未挂载——TenantHostMiddleware 需要 "
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"lifespan(或测试注入缝)先加载 TenantRegistry")
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try:
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runtime, site = await registry.resolve_site(_host_from_scope(scope))
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except UnknownTenantError:
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if scope["type"] == "websocket":
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await _close_ws(receive, send, 1008, "unknown host")
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else:
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await PlainTextResponse("Not Found", status_code=404)(
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scope, receive, send)
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return
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except TenantDisabledError:
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if scope["type"] == "websocket":
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await _close_ws(receive, send, 1013, "service paused")
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else:
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await HTMLResponse(PAUSE_PAGE, status_code=503)(
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scope, receive, send)
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return
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state = scope.setdefault("state", {})
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state["tenant"] = runtime
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state["site"] = site
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await self.app(scope, receive, send)
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