cherrypy和MySQL连用_在Cherrypy和SQLAlchemy中，如何在同一个请求中使用多个数据库？...
我的应用程序使用类似于this的技术连接到多个数据库。只要我不尝试在同一个请求中访问不同的数据库，它就可以工作。在回顾上述脚本后，我看到他们为此写了一篇评论：SQLAlchemy integration for CherryPy,
such that you can access multiple databases,
but only one of these databases per request or thread.
我的应用程序现在要求我从数据库A和数据库B获取数据。是否可以在一个请求中完成此操作？在
有关来源和示例，请参见以下内容：
工作示例1:
^{pr2}$
工作示例2:from model import meta
my_user = meta.user_session().query(User).filter(
User.id == 1
).one()
错误示例：from model import meta
my_object_instance = meta.main_session().query(MyObject).filter(
MyObject.id == 1
).one()
my_user = meta.user_session().query(User).filter(
User.id == 1
).one()
此错误包含：(sqlalchemy.exc.ProgrammingError) (1146, "Table 'main_db.user' doesn't exist")
来源：# meta.py
import cherrypy
import sqlalchemy
from sqlalchemy import MetaData
from sqlalchemy.orm import scoped_session, sessionmaker
from sqlalchemy.ext.declarative import declarative_base
# Return an Engine
def create_engine(defaultschema = True, schema = "", **kwargs):
# A blank DB is the same as no DB so to specify a non-schema-specific connection just override with defaultschema = False
connectionString = 'mysql://%s:%s@%s/%s?charset=utf8' % (
store['application'].config['main']['database-server-config-username'],
store['application'].config['main']['database-server-config-password'],
store['application'].config['main']['database-server-config-host'],
store['application'].config['main']['database-server-config-defaultschema'] if defaultschema else schema
)
# Create engine object. we pass **kwargs through so this call can be extended
return sqlalchemy.create_engine(connectionString, echo=True, pool_recycle=10, echo_pool=True, encoding='utf-8', **kwargs)
# Engines
main_engine = create_engine()
user_engine = None
# Sessions
_main_session = None
_user_session = None
# Metadata
main_metadata = MetaData()
main_metadata.bind = main_engine
user_metadata = MetaData()
# No idea what bases are/do but nothing works without them
main_base = declarative_base(metadata = main_metadata)
user_base = declarative_base(metadata = user_metadata)
# An easy collection of user database connections
engines = {}
# Each thread gets a session based on this object
GlobalSession = scoped_session(sessionmaker(autoflush=True, autocommit=False, expire_on_commit=False))
def main_session():
_main_session = cherrypy.request.main_dbsession
_main_session.configure(bind=main_engine)
return _main_session
def user_session():
_user_session = cherrypy.request.user_dbsession
_user_session.configure(bind = get_user_engine())
return _user_session
def get_user_engine():
# Get dburi from the users instance
dburi = cherrypy.session['auth']['user'].instance.database
# Store this engine for future use
if dburi in engines:
engine = engines.get(dburi)
else:
engine = engines[dburi] = create_engine(defaultschema = False, schema = dburi)
# Return Engine
return engine
def get_user_metadata():
user_metadata.bind = get_user_engine()
return user_metadata
# open a new session for the life of the request
def open_dbsession():
cherrypy.request.user_dbsession = cherrypy.thread_data.scoped_session_class
cherrypy.request.main_dbsession = cherrypy.thread_data.scoped_session_class
return
# close the session for this request
def close_dbsession():
if hasattr(cherrypy.request, "user_dbsession"):
try:
cherrypy.request.user_dbsession.flush()
cherrypy.request.user_dbsession.remove()
del cherrypy.request.user_dbsession
except:
pass
if hasattr(cherrypy.request, "main_dbsession"):
try:
cherrypy.request.main_dbsession.flush()
cherrypy.request.main_dbsession.remove()
del cherrypy.request.main_dbsession
except:
pass
return
# initialize the session factory class for the selected thread
def connect(thread_index):
cherrypy.thread_data.scoped_session_class = scoped_session(sessionmaker(autoflush=True, autocommit=False))
return
# add the hooks to cherrypy
cherrypy.tools.dbsession_open = cherrypy.Tool('on_start_resource', open_dbsession)
cherrypy.tools.dbsession_close = cherrypy.Tool('on_end_resource', close_dbsession)
cherrypy.engine.subscribe('start_thread', connect)