1 files changed, 146 insertions, 0 deletions
diff --git a/lib/sqlalchemy/pool/dbapi_proxy.py b/lib/sqlalchemy/pool/dbapi_proxy.py
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+++ b/lib/sqlalchemy/pool/dbapi_proxy.py
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+# sqlalchemy/pool/dbapi_proxy.py
+# Copyright (C) 2005-2018 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 ..util import threading
+
+proxies = {}
+
+
+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)]
+        )