codex

pricewatch/app/db/connection.py

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+"""
+Gestion des connexions PostgreSQL pour PriceWatch Phase 2.
+
+Fournit:
+- Engine SQLAlchemy avec connection pooling
+- Session factory avec context manager
+- Initialisation des tables
+- Health check
+
+Justification technique:
+- Connection pooling: réutilisation connexions pour performance
+- Context manager: garantit fermeture session (pas de leak)
+- pool_pre_ping: vérifie connexion avant usage (robustesse)
+- echo=debug: logs SQL en mode debug
+"""
+
+from contextlib import contextmanager
+from typing import Generator, Optional
+
+from sqlalchemy import create_engine, text
+from sqlalchemy.engine import Engine
+from sqlalchemy.engine.url import make_url
+from sqlalchemy.exc import OperationalError, SQLAlchemyError
+from sqlalchemy.orm import Session, sessionmaker
+
+from pricewatch.app.core.config import AppConfig, get_config
+from pricewatch.app.core.logging import get_logger
+from pricewatch.app.db.models import Base
+
+logger = get_logger("db.connection")
+
+# Global engine instance (singleton)
+_engine: Optional[Engine] = None
+_session_factory: Optional[sessionmaker] = None
+
+
+def get_engine(config: Optional[AppConfig] = None) -> Engine:
+    """
+    Récupère ou crée l'Engine SQLAlchemy (singleton).
+
+    Args:
+        config: Configuration app (utilise get_config() si None)
+
+    Returns:
+        Engine SQLAlchemy configuré
+
+    Justification:
+    - Singleton: une seule pool de connexions par application
+    - pool_pre_ping: vérifie connexion avant usage (évite "connection closed")
+    - pool_size=5, max_overflow=10: limite connexions (15 max)
+    - echo=debug: logs SQL pour debugging
+    """
+    global _engine
+
+    if _engine is None:
+        if config is None:
+            config = get_config()
+
+        db_url = config.db.url
+        url = make_url(db_url)
+        is_sqlite = url.get_backend_name() == "sqlite"
+
+        logger.info(f"Creating database engine: {db_url}")
+
+        engine_kwargs = {
+            "pool_pre_ping": True,
+            "pool_recycle": 3600,
+            "echo": config.debug,
+        }
+
+        if not is_sqlite:
+            engine_kwargs.update(
+                {
+                    "pool_size": 5,
+                    "max_overflow": 10,
+                }
+            )
+
+        _engine = create_engine(db_url, **engine_kwargs)
+
+        logger.info("Database engine created successfully")
+
+    return _engine
+
+
+def init_db(config: Optional[AppConfig] = None) -> None:
+    """
+    Initialise la base de données (crée toutes les tables).
+
+    Args:
+        config: Configuration app (utilise get_config() si None)
+
+    Raises:
+        OperationalError: Si connexion impossible
+        SQLAlchemyError: Si création tables échoue
+
+    Note:
+        Utilise Base.metadata.create_all() - idempotent (ne crash pas si tables existent)
+    """
+    if config is None:
+        config = get_config()
+
+    logger.info("Initializing database...")
+
+    try:
+        engine = get_engine(config)
+
+        # Créer toutes les tables définies dans Base.metadata
+        Base.metadata.create_all(bind=engine)
+
+        logger.info("Database initialized successfully")
+        logger.info(f"Tables created: {', '.join(Base.metadata.tables.keys())}")
+
+    except OperationalError as e:
+        logger.error(f"Failed to connect to database: {e}")
+        raise
+    except SQLAlchemyError as e:
+        logger.error(f"Failed to create tables: {e}")
+        raise
+
+
+def get_session_factory(config: Optional[AppConfig] = None) -> sessionmaker:
+    """
+    Récupère ou crée la session factory (singleton).
+
+    Args:
+        config: Configuration app (utilise get_config() si None)
+
+    Returns:
+        Session factory SQLAlchemy
+
+    Justification:
+    - expire_on_commit=False: objets restent accessibles après commit
+    - autocommit=False, autoflush=False: contrôle explicite
+    """
+    global _session_factory
+
+    if _session_factory is None:
+        engine = get_engine(config)
+
+        _session_factory = sessionmaker(
+            bind=engine,
+            expire_on_commit=False,  # Objets restent accessibles après commit
+            autocommit=False,  # Contrôle explicite du commit
+            autoflush=False,  # Contrôle explicite du flush
+        )
+
+        logger.debug("Session factory created")
+
+    return _session_factory
+
+
+@contextmanager
+def get_session(config: Optional[AppConfig] = None) -> Generator[Session, None, None]:
+    """
+    Context manager pour session SQLAlchemy.
+
+    Args:
+        config: Configuration app (utilise get_config() si None)
+
+    Yields:
+        Session SQLAlchemy
+
+    Usage:
+        with get_session() as session:
+            product = session.query(Product).filter_by(reference="B08N5WRWNW").first()
+            session.commit()
+
+    Justification:
+    - Context manager: garantit fermeture session (pas de leak)
+    - Rollback automatique sur exception
+    - Close automatique en fin de bloc
+    """
+    factory = get_session_factory(config)
+    session = factory()
+
+    try:
+        logger.debug("Session opened")
+        yield session
+    except Exception as e:
+        logger.error(f"Session error, rolling back: {e}")
+        session.rollback()
+        raise
+    finally:
+        logger.debug("Session closed")
+        session.close()
+
+
+def check_db_connection(config: Optional[AppConfig] = None) -> bool:
+    """
+    Vérifie la connexion à la base de données (health check).
+
+    Args:
+        config: Configuration app (utilise get_config() si None)
+
+    Returns:
+        True si connexion OK, False sinon
+
+    Note:
+        Execute une query simple: SELECT 1
+    """
+    if config is None:
+        config = get_config()
+
+    try:
+        engine = get_engine(config)
+
+        with engine.connect() as conn:
+            result = conn.execute(text("SELECT 1"))
+            result.scalar()
+
+        logger.info("Database connection OK")
+        return True
+
+    except OperationalError as e:
+        logger.error(f"Database connection failed: {e}")
+        return False
+    except SQLAlchemyError as e:
+        logger.error(f"Database health check failed: {e}")
+        return False
+
+
+def reset_engine() -> None:
+    """
+    Reset l'engine global (pour tests).
+
+    Note:
+        Dispose l'engine et reset les singletons.
+    """
+    global _engine, _session_factory
+
+    if _engine is not None:
+        logger.debug("Disposing database engine")
+        _engine.dispose()
+        _engine = None
+
+    _session_factory = None
+    logger.debug("Engine reset complete")