주-복제본 복제

# Python - SQLAlchemy 읽기/쓰기 분리
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

# Primary (쓰기용)
primary_engine = create_engine('postgresql://primary-host:5432/mydb')

# Replica (읽기용)
replica_engine = create_engine('postgresql://replica-host:5432/mydb')

PrimarySession = sessionmaker(bind=primary_engine)
ReplicaSession = sessionmaker(bind=replica_engine)

class DatabaseRouter:
    def get_session(self, readonly=False):
        if readonly:
            return ReplicaSession()
        return PrimarySession()

# 사용 예시
router = DatabaseRouter()

# 쓰기 작업 - Primary로
with router.get_session(readonly=False) as session:
    new_user = User(name="홍길동", email="hong@example.com")
    session.add(new_user)
    session.commit()

# 읽기 작업 - Replica로
with router.get_session(readonly=True) as session:
    users = session.query(User).filter(User.active == True).all()

# Django - 데이터베이스 라우터 설정
# settings.py
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'HOST': 'primary-host',
        'NAME': 'mydb',
    },
    'replica': {
        'ENGINE': 'django.db.backends.postgresql',
        'HOST': 'replica-host',
        'NAME': 'mydb',
    }
}

# routers.py
class PrimaryReplicaRouter:
    def db_for_read(self, model, **hints):
        return 'replica'

    def db_for_write(self, model, **hints):
        return 'default'

    def allow_relation(self, obj1, obj2, **hints):
        return True

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        return db == 'default'