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"""Define different strategies for creating new instances of sql.Engine.
By default there are two, one which is the "thread-local" strategy,
one which is the "plain" strategy.
New strategies can be added via constructing a new EngineStrategy
object which will add itself to the list of available strategies here,
or replace one of the existing name. this can be accomplished via a
mod; see the sqlalchemy/mods package for details.
"""
from sqlalchemy.engine import base, default, threadlocal, url
from sqlalchemy import util, exceptions
from sqlalchemy import pool as poollib
strategies = {}
class EngineStrategy(object):
"""Define a function that receives input arguments and produces an
instance of sql.Engine, typically an instance
sqlalchemy.engine.base.Engine or a subclass.
"""
def __init__(self, name):
"""Construct a new EngineStrategy object.
Sets it in the list of available strategies under this name.
"""
self.name = name
strategies[self.name] = self
def create(self, *args, **kwargs):
"""Given arguments, returns a new sql.Engine instance."""
raise NotImplementedError()
class DefaultEngineStrategy(EngineStrategy):
def create(self, name_or_url, **kwargs):
# create url.URL object
u = url.make_url(name_or_url)
# get module from sqlalchemy.databases
module = u.get_module()
dialect_args = {}
# consume dialect arguments from kwargs
for k in util.get_cls_kwargs(module.dialect):
if k in kwargs:
dialect_args[k] = kwargs.pop(k)
dbapi = kwargs.pop('module', None)
if dbapi is None:
dbapi_args = {}
for k in util.get_func_kwargs(module.dbapi):
if k in kwargs:
dbapi_args[k] = kwargs.pop(k)
dbapi = module.dbapi(**dbapi_args)
dialect_args['dbapi'] = dbapi
# create dialect
dialect = module.dialect(**dialect_args)
# assemble connection arguments
(cargs, cparams) = dialect.create_connect_args(u)
cparams.update(kwargs.pop('connect_args', {}))
# look for existing pool or create
pool = kwargs.pop('pool', None)
if pool is None:
def connect():
try:
return dbapi.connect(*cargs, **cparams)
except Exception, e:
raise exceptions.DBAPIError("Connection failed", e)
creator = kwargs.pop('creator', connect)
poolclass = kwargs.pop('poolclass', getattr(module, 'poolclass', poollib.QueuePool))
pool_args = {}
# consume pool arguments from kwargs, translating a few of the arguments
for k in util.get_cls_kwargs(poolclass):
tk = {'echo':'echo_pool', 'timeout':'pool_timeout', 'recycle':'pool_recycle'}.get(k, k)
if tk in kwargs:
pool_args[k] = kwargs.pop(tk)
pool_args['use_threadlocal'] = self.pool_threadlocal()
pool = poolclass(creator, disconnect_checker=dialect.get_disconnect_checker(), **pool_args)
else:
if isinstance(pool, poollib._DBProxy):
pool = pool.get_pool(*cargs, **cparams)
else:
pool = pool
provider = self.get_pool_provider(pool)
# create engine.
engineclass = self.get_engine_cls()
engine_args = {}
for k in util.get_cls_kwargs(engineclass):
if k in kwargs:
engine_args[k] = kwargs.pop(k)
# all kwargs should be consumed
if len(kwargs):
raise TypeError("Invalid argument(s) %s sent to create_engine(), using configuration %s/%s/%s. Please check that the keyword arguments are appropriate for this combination of components." % (','.join(["'%s'" % k for k in kwargs]), dialect.__class__.__name__, pool.__class__.__name__, engineclass.__name__))
return engineclass(provider, dialect, **engine_args)
def pool_threadlocal(self):
raise NotImplementedError()
def get_pool_provider(self, pool):
raise NotImplementedError()
def get_engine_cls(self):
raise NotImplementedError()
class PlainEngineStrategy(DefaultEngineStrategy):
def __init__(self):
DefaultEngineStrategy.__init__(self, 'plain')
def pool_threadlocal(self):
return False
def get_pool_provider(self, pool):
return default.PoolConnectionProvider(pool)
def get_engine_cls(self):
return base.Engine
PlainEngineStrategy()
class ThreadLocalEngineStrategy(DefaultEngineStrategy):
def __init__(self):
DefaultEngineStrategy.__init__(self, 'threadlocal')
def pool_threadlocal(self):
return True
def get_pool_provider(self, pool):
return threadlocal.TLocalConnectionProvider(pool)
def get_engine_cls(self):
return threadlocal.TLEngine
ThreadLocalEngineStrategy()
class MockEngineStrategy(EngineStrategy):
"""Produces a single Connection object which dispatches statement executions
to a passed-in function"""
def __init__(self):
EngineStrategy.__init__(self, 'mock')
def create(self, name_or_url, executor, **kwargs):
# create url.URL object
u = url.make_url(name_or_url)
# get module from sqlalchemy.databases
module = u.get_module()
dialect_args = {}
# consume dialect arguments from kwargs
for k in util.get_cls_kwargs(module.dialect):
if k in kwargs:
dialect_args[k] = kwargs.pop(k)
# create dialect
dialect = module.dialect(**dialect_args)
return MockEngineStrategy.MockConnection(dialect, executor)
class MockConnection(base.Connectable):
def __init__(self, dialect, execute):
self._dialect = dialect
self.execute = execute
engine = property(lambda s: s)
dialect = property(lambda s:s._dialect)
def contextual_connect(self):
return self
def create(self, entity, **kwargs):
kwargs['checkfirst'] = False
entity.accept_visitor(self.dialect.schemagenerator(self, **kwargs))
def drop(self, entity, **kwargs):
kwargs['checkfirst'] = False
entity.accept_visitor(self.dialect.schemadropper(self, **kwargs))
def execute(self, object, *multiparams, **params):
raise NotImplementedError()
MockEngineStrategy()
|
