gistfile1.py

import eventlet.patcher
eventlet.patcher.monkey_patch()

import eventlet.db_pool
import sqlalchemy.orm
import sqlalchemy.pool
import psycopg2

_ENGINE = None
_MAKER = None


pgDBurl="postgresql://"


def get_session(autocommit=True, expire_on_commit=False):
    """Return a SQLAlchemy session."""
    global _ENGINE, _MAKER

    if _MAKER is None or _ENGINE is None:
        _ENGINE = get_engine()
        _MAKER = get_maker(_ENGINE, autocommit, expire_on_commit)

    session = _MAKER()
    return session

def get_maker(engine, autocommit=True, expire_on_commit=False):
    """Return a SQLAlchemy sessionmaker using the given engine."""
    return sqlalchemy.orm.sessionmaker(bind=engine,
                                       autocommit=autocommit,
                                       expire_on_commit=expire_on_commit)

def get_engine():
    """Return a SQLAlchemy engine."""

    poolCreator = eventlet.db_pool.ConnectionPool(psycopg2, host=_host, user=_user, password=_passw, dbname=_db, min_size=1, max_size=10, max_idle=60)
    return sqlalchemy.create_engine(pgDBurl, pool_recycle=180, pool_size=4, pool_timeout=30, max_overflow=0, creator=poolCreator.create)