117 lines
4.5 KiB
Python
117 lines
4.5 KiB
Python
"""会话存储的 MongoDB 实现，方法语义与内存实现一致"""
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from datetime import UTC, datetime, timedelta
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from uuid import uuid4
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from bson.codec_options import CodecOptions
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from pymongo import ASCENDING, DESCENDING
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from pymongo.asynchronous.database import AsyncDatabase
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from app.config import settings
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from app.schemas.conversation import Turn
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# 单次清理的空会话上限，避免积压时一次请求扫描过多
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PURGE_BATCH = 200
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def _now() -> datetime:
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return datetime.now(UTC)
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class MongoConversationStore:
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def __init__(
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self, db: AsyncDatabase, empty_ttl: int | None = None, prefix: str = ""
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):
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ttl = empty_ttl if empty_ttl is not None else settings.conversation_empty_ttl
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self._empty_ttl = timedelta(seconds=ttl)
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# 读回的时间统一带 UTC 时区，与 Turn 的时间保持一致；集合名前缀用于测试隔离
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options = CodecOptions(tz_aware=True, tzinfo=UTC)
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self._conversations = db.get_collection(
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f"{prefix}conversations", codec_options=options
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)
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self._turns = db.get_collection(f"{prefix}turns", codec_options=options)
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async def ensure_indexes(self) -> None:
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# 创建索引是幂等的，启动时调用一次即可
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# 同一任务只有一轮，恢复后的重复写入靠唯一索引落到同一条记录
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await self._turns.create_index(
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[("conversation_id", ASCENDING), ("thread_id", ASCENDING)], unique=True
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)
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await self._turns.create_index(
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[("conversation_id", ASCENDING), ("created_at", ASCENDING)]
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)
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# 空会话清理按创建时间扫描
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await self._conversations.create_index("created_at")
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async def _purge_expired(self) -> None:
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# 只清理没有任何轮次且超过保留时长的空会话，有对话的会话不受影响
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deadline = _now() - self._empty_ttl
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expired = await (
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self._conversations.find({"created_at": {"$lt": deadline}}, {"_id": 1})
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.limit(PURGE_BATCH)
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.to_list()
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)
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ids = [item["_id"] for item in expired]
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if not ids:
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return
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used = set(
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await self._turns.distinct(
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"conversation_id", {"conversation_id": {"$in": ids}}
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)
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)
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empty = [item for item in ids if item not in used]
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if empty:
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await self._conversations.delete_many({"_id": {"$in": empty}})
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async def create(self) -> str:
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await self._purge_expired()
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conversation_id = str(uuid4())
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# user_id 为后续长期记忆预留，当前恒为空
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await self._conversations.insert_one(
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{"_id": conversation_id, "created_at": _now(), "user_id": None}
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)
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return conversation_id
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async def exists(self, conversation_id: str) -> bool:
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document = await self._conversations.find_one({"_id": conversation_id})
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if document is None:
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return False
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if document["created_at"] >= _now() - self._empty_ttl:
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return True
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# 超过空会话保留时长后，只有已产生对话的会话仍视为存在
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return (
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await self._turns.find_one({"conversation_id": conversation_id}, {"_id": 1})
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is not None
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)
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async def load_turns(self, conversation_id: str, limit: int | None) -> list[Turn]:
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if limit == 0:
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return []
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cursor = self._turns.find({"conversation_id": conversation_id})
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if limit is None:
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documents = await cursor.sort(
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[("created_at", ASCENDING), ("_id", ASCENDING)]
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).to_list()
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else:
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# 倒序取最近 limit 轮，再反转为时间正序
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documents = await (
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cursor.sort([("created_at", DESCENDING), ("_id", DESCENDING)])
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.limit(limit)
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.to_list()
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)
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documents.reverse()
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return [
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Turn.model_validate({k: v for k, v in item.items() if k != "_id"})
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for item in documents
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]
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async def save_turn(self, turn: Turn) -> None:
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data = turn.model_dump()
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created_at = data.pop("created_at")
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# 同一任务再次写入（澄清恢复后）保留首次创建时间，只更新内容
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await self._turns.update_one(
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{"conversation_id": turn.conversation_id, "thread_id": turn.thread_id},
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{"$set": data, "$setOnInsert": {"created_at": created_at}},
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upsert=True,
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)
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