129 lines
3.9 KiB
Python
129 lines
3.9 KiB
Python
# stanard imports
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import logging
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# third-party imports
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from sqlalchemy import Column, Integer
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from sqlalchemy.ext.declarative import declarative_base
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from sqlalchemy import create_engine
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from sqlalchemy.orm import sessionmaker
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from sqlalchemy.pool import (
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StaticPool,
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QueuePool,
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AssertionPool,
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NullPool,
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)
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logg = logging.getLogger()
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Model = declarative_base(name='Model')
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class SessionBase(Model):
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"""The base object for all SQLAlchemy enabled models. All other models must extend this.
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"""
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__abstract__ = True
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id = Column(Integer, primary_key=True)
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engine = None
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"""Database connection engine of the running aplication"""
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sessionmaker = None
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"""Factory object responsible for creating sessions from the connection pool"""
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transactional = True
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"""Whether the database backend supports query transactions. Should be explicitly set by initialization code"""
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poolable = True
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"""Whether the database backend supports connection pools. Should be explicitly set by initialization code"""
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procedural = True
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"""Whether the database backend supports stored procedures"""
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localsessions = {}
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"""Contains dictionary of sessions initiated by db model components"""
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@staticmethod
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def create_session():
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"""Creates a new database session.
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"""
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return SessionBase.sessionmaker()
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@staticmethod
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def _set_engine(engine):
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"""Sets the database engine static property
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"""
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SessionBase.engine = engine
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SessionBase.sessionmaker = sessionmaker(bind=SessionBase.engine)
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@staticmethod
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def connect(dsn, pool_size=16, debug=False):
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"""Create new database connection engine and connect to database backend.
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:param dsn: DSN string defining connection.
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:type dsn: str
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"""
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e = None
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if SessionBase.poolable:
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poolclass = QueuePool
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if pool_size > 1:
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logg.info('db using queue pool')
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e = create_engine(
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dsn,
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max_overflow=pool_size*3,
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pool_pre_ping=True,
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pool_size=pool_size,
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pool_recycle=60,
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poolclass=poolclass,
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echo=debug,
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)
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else:
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if pool_size == 0:
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logg.info('db using nullpool')
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poolclass = NullPool
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elif debug:
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logg.info('db using assertion pool')
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poolclass = AssertionPool
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else:
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logg.info('db using static pool')
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poolclass = StaticPool
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e = create_engine(
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dsn,
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poolclass=poolclass,
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echo=debug,
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)
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else:
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logg.info('db not poolable')
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e = create_engine(
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dsn,
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echo=debug,
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)
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SessionBase._set_engine(e)
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@staticmethod
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def disconnect():
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"""Disconnect from database and free resources.
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"""
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SessionBase.engine.dispose()
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SessionBase.engine = None
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@staticmethod
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def bind_session(session=None):
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localsession = session
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if localsession == None:
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localsession = SessionBase.create_session()
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localsession_key = str(id(localsession))
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logg.debug('creating new session {}'.format(localsession_key))
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SessionBase.localsessions[localsession_key] = localsession
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return localsession
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@staticmethod
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def release_session(session=None):
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session_key = str(id(session))
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if SessionBase.localsessions.get(session_key) != None:
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logg.debug('commit and destroy session {}'.format(session_key))
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session.commit()
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session.close()
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