Adolfo Delorenzo
2116059157
- Celery workers use NullPool to avoid "Future attached to a different loop" errors from stale pooled async connections across asyncio.run() calls. FastAPI keeps regular pool (single event loop, safe to reuse). - Skip pgvector similarity search when no conversation history exists (first message) — saves ~3s embedding + query overhead. - Wrap pgvector retrieval in try/except to prevent DB errors from blocking the LLM response. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
70 lines
2.3 KiB
Python
70 lines
2.3 KiB
Python
"""
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Async SQLAlchemy engine and session factory.
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Usage in FastAPI:
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async def route(session: AsyncSession = Depends(get_session)):
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...
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Usage in tests:
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async with async_session_factory() as session:
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...
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"""
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from __future__ import annotations
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from collections.abc import AsyncGenerator
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import os
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from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession, async_sessionmaker, create_async_engine
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from sqlalchemy.pool import NullPool
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from shared.config import settings
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# ---------------------------------------------------------------------------
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# Engine — one per process; shared across all requests
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#
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# Celery workers use asyncio.run() per task, creating a new event loop each
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# time. Connection pools hold connections bound to the previous (closed) loop,
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# causing "Future attached to a different loop" errors. NullPool avoids this
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# by never reusing connections. FastAPI (single event loop) can safely use a
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# regular pool, but NullPool works fine there too with minimal overhead.
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# ---------------------------------------------------------------------------
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_is_celery_worker = "celery" in os.environ.get("_", "") or "celery" in " ".join(os.sys.argv)
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engine: AsyncEngine = create_async_engine(
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settings.database_url,
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echo=settings.debug,
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**({"poolclass": NullPool} if _is_celery_worker else {
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"pool_pre_ping": True,
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"pool_size": 10,
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"max_overflow": 20,
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}),
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)
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# ---------------------------------------------------------------------------
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# Session factory
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# ---------------------------------------------------------------------------
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async_session_factory: async_sessionmaker[AsyncSession] = async_sessionmaker(
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engine,
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class_=AsyncSession,
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expire_on_commit=False,
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)
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async def get_session() -> AsyncGenerator[AsyncSession, None]:
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"""
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FastAPI dependency that yields an async database session.
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The session is automatically closed (and the connection returned to the
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pool) when the request context exits, even if an exception is raised.
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Example:
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@router.get("/agents")
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async def list_agents(session: AsyncSession = Depends(get_session)):
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result = await session.execute(select(Agent))
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return result.scalars().all()
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"""
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async with async_session_factory() as session:
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yield session
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