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python37
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sqlalchemy
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pool
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dbapi_proxy.py
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# sqlalchemy/pool/dbapi_proxy.py # Copyright (C) 2005-2019 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """DBAPI proxy utility. Provides transparent connection pooling on top of a Python DBAPI. This is legacy SQLAlchemy functionality that is not typically used today. """ from .impl import QueuePool from .. import util from ..util import threading proxies = {} @util.deprecated( "1.3", "The :func:`.pool.manage` function is deprecated, and will be " "removed in a future release.", ) def manage(module, **params): r"""Return a proxy for a DB-API module that automatically pools connections. Given a DB-API 2.0 module and pool management parameters, returns a proxy for the module that will automatically pool connections, creating new connection pools for each distinct set of connection arguments sent to the decorated module's connect() function. :param module: a DB-API 2.0 database module :param poolclass: the class used by the pool module to provide pooling. Defaults to :class:`.QueuePool`. :param \**params: will be passed through to *poolclass* """ try: return proxies[module] except KeyError: return proxies.setdefault(module, _DBProxy(module, **params)) def clear_managers(): """Remove all current DB-API 2.0 managers. All pools and connections are disposed. """ for manager in proxies.values(): manager.close() proxies.clear() class _DBProxy(object): """Layers connection pooling behavior on top of a standard DB-API module. Proxies a DB-API 2.0 connect() call to a connection pool keyed to the specific connect parameters. Other functions and attributes are delegated to the underlying DB-API module. """ def __init__(self, module, poolclass=QueuePool, **kw): """Initializes a new proxy. module a DB-API 2.0 module poolclass a Pool class, defaulting to QueuePool Other parameters are sent to the Pool object's constructor. """ self.module = module self.kw = kw self.poolclass = poolclass self.pools = {} self._create_pool_mutex = threading.Lock() def close(self): for key in list(self.pools): del self.pools[key] def __del__(self): self.close() def __getattr__(self, key): return getattr(self.module, key) def get_pool(self, *args, **kw): key = self._serialize(*args, **kw) try: return self.pools[key] except KeyError: self._create_pool_mutex.acquire() try: if key not in self.pools: kw.pop("sa_pool_key", None) pool = self.poolclass( lambda: self.module.connect(*args, **kw), **self.kw ) self.pools[key] = pool return pool else: return self.pools[key] finally: self._create_pool_mutex.release() def connect(self, *args, **kw): """Activate a connection to the database. Connect to the database using this DBProxy's module and the given connect arguments. If the arguments match an existing pool, the connection will be returned from the pool's current thread-local connection instance, or if there is no thread-local connection instance it will be checked out from the set of pooled connections. If the pool has no available connections and allows new connections to be created, a new database connection will be made. """ return self.get_pool(*args, **kw).connect() def dispose(self, *args, **kw): """Dispose the pool referenced by the given connect arguments.""" key = self._serialize(*args, **kw) try: del self.pools[key] except KeyError: pass def _serialize(self, *args, **kw): if "sa_pool_key" in kw: return kw["sa_pool_key"] return tuple(list(args) + [(k, kw[k]) for k in sorted(kw)])