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import inspect
import os
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.utils.importlib import import_module
DEFAULT_DB_ALIAS = 'default'
# Define some exceptions that mirror the PEP249 interface.
# We will rethrow any backend-specific errors using these
# common wrappers
class DatabaseError(Exception):
pass
class IntegrityError(DatabaseError):
pass
def load_backend(backend_name):
try:
module = import_module('.base', 'django.db.backends.%s' % backend_name)
import warnings
warnings.warn(
"Short names for DATABASE_ENGINE are deprecated; prepend with 'django.db.backends.'",
PendingDeprecationWarning
)
return module
except ImportError, e:
# Look for a fully qualified database backend name
try:
return import_module('.base', backend_name)
except ImportError, e_user:
# The database backend wasn't found. Display a helpful error message
# listing all possible (built-in) database backends.
backend_dir = os.path.join(os.path.dirname(__file__), 'backends')
try:
available_backends = [f for f in os.listdir(backend_dir)
if os.path.isdir(os.path.join(backend_dir, f))
and not f.startswith('.')]
except EnvironmentError:
available_backends = []
available_backends.sort()
if backend_name not in available_backends:
error_msg = ("%r isn't an available database backend. \n" +
"Try using django.db.backends.XXX, where XXX is one of:\n %s\n" +
"Error was: %s") % \
(backend_name, ", ".join(map(repr, available_backends)), e_user)
raise ImproperlyConfigured(error_msg)
else:
raise # If there's some other error, this must be an error in Django itself.
class ConnectionDoesNotExist(Exception):
pass
class ConnectionHandler(object):
def __init__(self, databases):
self.databases = databases
self._connections = {}
def ensure_defaults(self, alias):
"""
Puts the defaults into the settings dictionary for a given connection
where no settings is provided.
"""
try:
conn = self.databases[alias]
except KeyError:
raise ConnectionDoesNotExist("The connection %s doesn't exist" % alias)
conn.setdefault('ENGINE', 'django.db.backends.dummy')
if conn['ENGINE'] == 'django.db.backends.' or not conn['ENGINE']:
conn['ENGINE'] = 'django.db.backends.dummy'
conn.setdefault('OPTIONS', {})
conn.setdefault('TEST_CHARSET', None)
conn.setdefault('TEST_COLLATION', None)
conn.setdefault('TEST_NAME', None)
conn.setdefault('TEST_MIRROR', None)
conn.setdefault('TIME_ZONE', settings.TIME_ZONE)
for setting in ('NAME', 'USER', 'PASSWORD', 'HOST', 'PORT'):
conn.setdefault(setting, '')
def __getitem__(self, alias):
if alias in self._connections:
return self._connections[alias]
self.ensure_defaults(alias)
db = self.databases[alias]
backend = load_backend(db['ENGINE'])
conn = backend.DatabaseWrapper(db, alias)
self._connections[alias] = conn
return conn
def __iter__(self):
return iter(self.databases)
def all(self):
return [self[alias] for alias in self]
class ConnectionRouter(object):
def __init__(self, routers):
self.routers = []
for r in routers:
if isinstance(r, basestring):
try:
module_name, klass_name = r.rsplit('.', 1)
module = import_module(module_name)
except ImportError, e:
raise ImproperlyConfigured('Error importing database router %s: "%s"' % (klass_name, e))
try:
router = getattr(module, klass_name)()
except AttributeError:
raise ImproperlyConfigured('Module "%s" does not define a database router name "%s"' % (module, klass_name))
else:
router = r
self.routers.append(router)
def _router_func(action):
def _route_db(self, model, **hints):
chosen_db = None
for router in self.routers:
try:
chosen_db = getattr(router, action)(model, **hints)
if chosen_db:
return chosen_db
except AttributeError:
# If the router doesn't have a method, skip to the next one.
pass
try:
return hints['instance']._state.db or DEFAULT_DB_ALIAS
except KeyError:
return DEFAULT_DB_ALIAS
return _route_db
db_for_read = _router_func('db_for_read')
db_for_write = _router_func('db_for_write')
def allow_relation(self, obj1, obj2, **hints):
for router in self.routers:
try:
allow = router.allow_relation(obj1, obj2, **hints)
if allow is not None:
return allow
except AttributeError:
# If the router doesn't have a method, skip to the next one.
pass
return obj1._state.db == obj2._state.db
def allow_syncdb(self, db, model):
for router in self.routers:
try:
allow = router.allow_syncdb(db, model)
if allow is not None:
return allow
except AttributeError:
# If the router doesn't have a method, skip to the next one.
pass
return True
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