65 lines
2.8 KiB
Python
65 lines
2.8 KiB
Python
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"""Neo4j 图驱动：把 neo4j 异步驱动封装成 `RelationshipService` 期望的 `GraphDriver` 协议。
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为什么单独一层：`RelationshipService` 只依赖 `execute_query(query, **params)` 这个窄协议，
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不关心底层是哪个驱动。有这一层，读服务、投影 worker、删除客户端就能共用同一套连接管理，
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也便于测试注入替身。
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**这层此前是空的** —— `app/service/relationship_service.py` 里的 `GraphDriver` 只有一个
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Protocol 声明，没有任何具体实现，组装层也没有装配它，所以读服务在运行期必然降级
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（`neo4j_unavailable`），这正是"Neo4j 连读适配器都没有"的根因。
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降级语义与 Milvus 侧保持一致：本层**不吞异常**（由调用方决定降级方式），但**构造失败返回 None**
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——图库不可用不该让应用起不来，也不该阻塞主链路。
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"""
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import logging
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from collections.abc import Sequence
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from typing import Any
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from app.core.config import get_settings
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logger = logging.getLogger(__name__)
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class Neo4jGraphDriver:
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"""`GraphDriver` 协议的 neo4j 实现。"""
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def __init__(self, driver: Any, database: str) -> None:
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self._driver = driver
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self._database = database
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async def execute_query(self, query: str, **parameters: Any) -> Sequence[Any]:
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"""执行一条 Cypher 并返回记录列表。
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查询文本由调用方提供（`RelationshipService` 与投影 worker 各自持有白名单：
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前者限制关系类型，后者只接受 `ALLOWED_RELATIONSHIPS` 中的关系），本层不做校验，
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只负责执行与结果整形——把校验放在拥有业务语义的地方，避免两处规则漂移。
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"""
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async with self._driver.session(database=self._database) as session:
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result = await session.run(query, **parameters)
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return list(await result.data())
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async def close(self) -> None:
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await self._driver.close()
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def build_graph_driver() -> Neo4jGraphDriver | None:
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"""按配置构造图驱动；依赖缺失或配置不全时返回 None（图能力关闭）。
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与 `get_vector_memory_adapter` 同一取向：外部依赖不可用只关闭对应能力，
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不让整个应用起不来。
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"""
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settings = get_settings()
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if not settings.neo4j_uri or not settings.neo4j_password:
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logger.warning("neo4j config incomplete; graph capability disabled")
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return None
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try:
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from neo4j import AsyncGraphDatabase
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except ImportError:
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logger.warning("neo4j driver not installed; graph capability disabled")
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return None
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driver = AsyncGraphDatabase.driver(
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settings.neo4j_uri, auth=(settings.neo4j_username, settings.neo4j_password)
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)
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return Neo4jGraphDriver(driver, settings.neo4j_database)
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