Mon application se connecte à plusieurs bases de données en utilisant une technique similaire à this. Cela fonctionne tant que je n'essaie pas d'accéder à différentes bases de données dans la même requête. Après avoir regardé en arrière au script ci-dessus, je vois qu'ils ont écrit un commentaire à cette fin:Comment utiliser plusieurs bases de données dans la même requête dans Cherrypy et SQLAlchemy?
SQLAlchemy integration for CherryPy,
such that you can access multiple databases,
but only one of these databases per request or thread.
Mon application me demande maintenant pour extraire des données de base de données A et base de données B. Est-il possible de le faire en une seule demande ?
S'il vous plaît voir ci-dessous pour les sources et les exemples:
de travail Exemple 1:
from model import meta
my_object_instance = meta.main_session().query(MyObject).filter(
MyObject.id == 1
).one()
Exemple de 2:
from model import meta
my_user = meta.user_session().query(User).filter(
User.id == 1
).one()
Exemple d'erreur:
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()
Cette erreur avec:
(sqlalchemy.exc.ProgrammingError) (1146, "Table 'main_db.user' doesn't exist")
Sources:
# 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:%[email protected]%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)
Je ne veux pas 'répondre' à ma propre question mais la solution semble être d'ajouter un scoped_session supplémentaire pour l'autre base de données dans 'connect', donc cela ressemble à' def connect (thread_index): cherrypy.thread_data.user_scoped_session_class = scoped_session (sessionmaker (autoflush = Vrai, autocommit = False)) cherrypy.thread_data.main_scoped_session_class = scoped_session (sessionmaker (autoflush = Vrai, autocommit = False)) return' puis les référence séparément dans 'open_dbsession' – OrganicPanda