257 lines
8.7 KiB
Python
257 lines
8.7 KiB
Python
"""PostgreSQL connection, async SQLAlchemy ORM and session management.
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Configuration comes from the environment, with `.env` read from the repo root or
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from `backend/` (`Db_USERNAME`, `Db_PASSWORD`, `Db_HOST`, `Db_PORT`, `Db_NAME`, and
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the `DB_*` tuning fields below). Alembic lives in `alembic_setup.py`; `init_db()`
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calls into it.
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app = FastAPI(lifespan=lifespan) # migrate on startup
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async def endpoint(db: AsyncSession = Depends(get_session)): ...
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async with session_scope() as db: ... # workers and scripts
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"""
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from __future__ import annotations
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import asyncio
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import os
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import logging
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from contextlib import asynccontextmanager
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from functools import lru_cache
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from pathlib import Path
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from typing import Annotated, Any, AsyncIterator, Sequence
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from pydantic import field_validator
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from pydantic_settings import BaseSettings, NoDecode, SettingsConfigDict
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from sqlalchemy import MetaData, text
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from sqlalchemy.engine import URL, make_url
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from sqlalchemy.ext.asyncio import (
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AsyncEngine,
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AsyncSession,
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async_sessionmaker,
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create_async_engine,
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)
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from sqlalchemy.orm import DeclarativeBase
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from sqlmodel import SQLModel
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from dotenv import load_dotenv
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load_dotenv()
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logger = logging.getLogger("db")
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BASE_DIR = Path(__file__).resolve().parent
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class Settings(BaseSettings):
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"""Every field is overridden by an environment variable of the same name."""
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model_config = SettingsConfigDict(
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env_file=(BASE_DIR.parent / ".env", BASE_DIR / ".env"), extra="ignore"
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)
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database_url: str = "" # full DSN; wins over the Db_* parts below
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db_username: str = os.getenv("DB_USERNAME")
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db_password: str = os.getenv("DB_PASSWORD")
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db_host: str = os.getenv("DB_HOST")
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db_port: int = int(os.getenv("DB_PORT"))
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db_name: str = os.getenv("DB_NAME")
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db_sslmode: str = "" # e.g. "require" on Azure
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db_schemas: Annotated[list[str], NoDecode] = "app"
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db_default_schema: str = "app" # schema for models that declare none
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db_echo: bool = False
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db_pool_size: int = 5
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db_max_overflow: int = 10
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db_pool_recycle: int = 1800
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db_connect_retries: int = 10
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db_auto_migrate: bool = True # run `upgrade head` on startup
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db_autogenerate: bool = True # write a revision when models drift from the schema
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db_model_modules: Annotated[list[str], NoDecode] = [] # empty means auto-discover
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app_name: str = "hr-ats-portal"
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@field_validator("db_schemas", "db_model_modules", mode="before")
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@classmethod
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def _csv(cls, value: Any) -> Any:
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if isinstance(value, str):
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return [item.strip() for item in value.split(",") if item.strip()]
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return value
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def url(self, *, async_driver: bool = True) -> URL:
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"""DSN with the driver forced; `sslmode` is translated to asyncpg's `ssl`."""
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url = (
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make_url(self.database_url)
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if self.database_url
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else URL.create(
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"postgresql",
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self.db_username,
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self.db_password,
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self.db_host,
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self.db_port,
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self.db_name,
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)
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)
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query = dict(url.query)
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if self.db_sslmode:
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query.setdefault("sslmode", self.db_sslmode)
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if async_driver and query.pop("sslmode", None) not in (None, "disable", "allow", "prefer"):
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query["ssl"] = "true"
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driver = "asyncpg" if async_driver else "psycopg2"
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return url.set(drivername=f"postgresql+{driver}", query=query)
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@lru_cache(maxsize=1)
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def get_settings() -> Settings:
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return Settings()
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def database_url(*, async_driver: bool = True, hide_password: bool = False) -> str:
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return get_settings().url(async_driver=async_driver).render_as_string(hide_password=hide_password)
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NAMING_CONVENTION = {
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"ix": "ix_%(table_name)s_%(column_0_N_name)s",
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"uq": "uq_%(table_name)s_%(column_0_N_name)s",
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"ck": "ck_%(table_name)s_%(constraint_name)s",
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"fk": "fk_%(table_name)s_%(column_0_N_name)s_%(referred_table_name)s",
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"pk": "pk_%(table_name)s",
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}
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class Base(DeclarativeBase):
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"""Declarative base every model must inherit from."""
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metadata = MetaData(
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naming_convention=NAMING_CONVENTION,
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schema=get_settings().db_default_schema or None,
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)
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# SQLModel keeps its own registry, so `SQLModel` tables would be invisible to the
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# Alembic autogenerate in alembic_setup.py, which diffs `Base.metadata` alone.
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# Pointing SQLModel at the same MetaData gives both styles one registry, and lets
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# SQLModel tables inherit the naming convention and the default schema above.
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SQLModel.metadata = Base.metadata
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_engine: AsyncEngine | None = None
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_sessionmaker: async_sessionmaker[AsyncSession] | None = None
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def get_engine() -> AsyncEngine:
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"""The process-wide AsyncEngine, created on first use."""
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global _engine
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if _engine is None:
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s = get_settings()
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_engine = create_async_engine(
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s.url(),
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echo=s.db_echo,
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pool_pre_ping=True,
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pool_size=s.db_pool_size,
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max_overflow=s.db_max_overflow,
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pool_recycle=s.db_pool_recycle,
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connect_args={
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"server_settings": {"timezone": "UTC", "application_name": s.app_name}
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},
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)
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return _engine
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def get_sessionmaker() -> async_sessionmaker[AsyncSession]:
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global _sessionmaker
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if _sessionmaker is None:
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_sessionmaker = async_sessionmaker(
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bind=get_engine(), class_=AsyncSession, expire_on_commit=False, autoflush=False
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)
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return _sessionmaker
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async def get_session() -> AsyncIterator[AsyncSession]:
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"""FastAPI dependency. Rolls back on error; committing is the caller's job."""
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async with get_sessionmaker()() as session:
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try:
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yield session
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except Exception:
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await session.rollback()
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raise
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@asynccontextmanager
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async def session_scope() -> AsyncIterator[AsyncSession]:
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"""Transactional session for scripts and workers: commits, or rolls back on error."""
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async with get_sessionmaker()() as session:
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try:
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yield session
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await session.commit()
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except Exception:
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await session.rollback()
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raise
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async def close_db() -> None:
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"""Dispose of the pool and reset the cached factories."""
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global _engine, _sessionmaker
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if _engine is not None:
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await _engine.dispose()
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logger.info("connection pool closed")
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_engine, _sessionmaker = None, None
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async def check_connection(retries: int | None = None, delay: float = 1.0) -> None:
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"""Wait for Postgres to answer `SELECT 1`, retrying with a capped backoff."""
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attempts = get_settings().db_connect_retries if retries is None else retries
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for attempt in range(1, max(attempts, 1) + 1):
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try:
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async with get_engine().connect() as conn:
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await conn.execute(text("SELECT 1"))
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logger.info("connected to %s", database_url(hide_password=True))
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return
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except Exception as exc:
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if attempt >= attempts:
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raise RuntimeError(f"cannot reach {database_url(hide_password=True)}") from exc
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logger.warning("database not ready (%s/%s): %s", attempt, attempts, exc)
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await asyncio.sleep(delay)
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delay = min(delay * 2, 10.0)
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async def create_schemas(schemas: Sequence[str] | None = None) -> None:
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"""`CREATE SCHEMA IF NOT EXISTS` for every configured schema."""
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names = list(get_settings().db_schemas if schemas is None else schemas)
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if not names:
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return
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async with get_engine().begin() as conn:
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for name in names:
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await conn.execute(text(f'CREATE SCHEMA IF NOT EXISTS "{name}"'))
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logger.info("schemas ensured: %s", ", ".join(names))
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async def init_db(*, migrate: bool | None = None, autogen: bool | None = None) -> None:
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"""Connect, create the schemas, then bring migrations up to head."""
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should_migrate = get_settings().db_auto_migrate if migrate is None else migrate
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await check_connection()
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await create_schemas()
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if should_migrate:
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from alembic_setup import migrate as run_migrations # local import: avoids a cycle
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await run_migrations(autogen=autogen)
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@asynccontextmanager
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async def lifespan(app: Any = None) -> AsyncIterator[None]:
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"""FastAPI lifespan: `app = FastAPI(lifespan=lifespan)`."""
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await init_db()
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try:
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yield
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finally:
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await close_db()
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if __name__ == "__main__":
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logging.basicConfig(level=logging.INFO, format="%(levelname)-8s %(name)s: %(message)s")
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async def _main() -> None:
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try:
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await init_db()
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finally:
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await close_db()
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asyncio.run(_main())
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