oslo.db/doc/source/usage.rst

Usage

To use oslo.db in a project:

* Session Handling

from oslo.config import cfg
from oslo.db.sqlalchemy import session as db_session

_FACADE = None

def _create_facade_lazily():
    global _FACADE
    if _FACADE is None:
        _FACADE = db_session.EngineFacade.from_config(cfg.CONF)
    return _FACADE

def get_engine():
    facade = _create_facade_lazily()
    return facade.get_engine()

def get_session(**kwargs):
    facade = _create_facade_lazily()
    return facade.get_session(**kwargs)

• Base class for models usage

  from oslo.db import models
  
  
  class ProjectSomething(models.TimestampMixin,
                         models.ModelBase):
      id = Column(Integer, primary_key=True)
      ...

• DB API backend support

  from oslo.config import cfg
  from oslo.db import api as db_api
  
  
  _BACKEND_MAPPING = {'sqlalchemy': 'project.db.sqlalchemy.api'}
  
  IMPL = db_api.DBAPI.from_config(cfg.CONF, backend_mapping=_BACKEND_MAPPING)
  
  def get_engine():
      return IMPL.get_engine()
  
  def get_session():
      return IMPL.get_session()
  
  # DB-API method
  def do_something(somethind_id):
      return IMPL.do_something(somethind_id)