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import cPickle
import logging
import pickle
from datetime import datetime
from beaker.container import OpenResourceNamespaceManager, Container
from beaker.exceptions import InvalidCacheBackendError, MissingCacheParameter
from beaker.synchronization import file_synchronizer, null_synchronizer
from beaker.util import verify_directory, SyncDict
log = logging.getLogger(__name__)
sa = None
class SqlaNamespaceManager(OpenResourceNamespaceManager):
binds = SyncDict()
tables = SyncDict()
@classmethod
def _init_dependencies(cls):
global sa
if sa is not None:
return
try:
import sqlalchemy as sa
except ImportError:
raise InvalidCacheBackendError("SQLAlchemy, which is required by "
"this backend, is not installed")
def __init__(self, namespace, bind, table, data_dir=None, lock_dir=None,
**kwargs):
"""Create a namespace manager for use with a database table via
SQLAlchemy.
``bind``
SQLAlchemy ``Engine`` or ``Connection`` object
``table``
SQLAlchemy ``Table`` object in which to store namespace data.
This should usually be something created by ``make_cache_table``.
"""
OpenResourceNamespaceManager.__init__(self, namespace)
if lock_dir:
self.lock_dir = lock_dir
elif data_dir:
self.lock_dir = data_dir + "/container_db_lock"
if self.lock_dir:
verify_directory(self.lock_dir)
self.bind = self.__class__.binds.get(str(bind.url), lambda: bind)
self.table = self.__class__.tables.get('%s:%s' % (bind.url, table.name),
lambda: table)
self.hash = {}
self._is_new = False
self.loaded = False
def get_access_lock(self):
return null_synchronizer()
def get_creation_lock(self, key):
return file_synchronizer(
identifier ="databasecontainer/funclock/%s" % self.namespace,
lock_dir=self.lock_dir)
def do_open(self, flags):
if self.loaded:
self.flags = flags
return
select = sa.select([self.table.c.data],
(self.table.c.namespace == self.namespace))
result = self.bind.execute(select).fetchone()
if not result:
self._is_new = True
self.hash = {}
else:
self._is_new = False
try:
self.hash = result['data']
except (IOError, OSError, EOFError, cPickle.PickleError,
pickle.PickleError):
log.debug("Couln't load pickle data, creating new storage")
self.hash = {}
self._is_new = True
self.flags = flags
self.loaded = True
def do_close(self):
if self.flags is not None and (self.flags == 'c' or self.flags == 'w'):
if self._is_new:
insert = self.table.insert()
self.bind.execute(insert, namespace=self.namespace, data=self.hash,
accessed=datetime.now(), created=datetime.now())
self._is_new = False
else:
update = self.table.update(self.table.c.namespace == self.namespace)
self.bind.execute(update, data=self.hash, accessed=datetime.now())
self.flags = None
def do_remove(self):
delete = self.table.delete(self.table.c.namespace == self.namespace)
self.bind.execute(delete)
self.hash = {}
self._is_new = True
def __getitem__(self, key):
return self.hash[key]
def __contains__(self, key):
return self.hash.has_key(key)
def __setitem__(self, key, value):
self.hash[key] = value
def __delitem__(self, key):
del self.hash[key]
def keys(self):
return self.hash.keys()
class SqlaContainer(Container):
namespace_manager = SqlaNamespaceManager
def make_cache_table(metadata, table_name='beaker_cache'):
"""Return a ``Table`` object suitable for storing cached values for the
namespace manager. Do not create the table."""
return sa.Table(table_name, metadata,
sa.Column('namespace', sa.String(255), primary_key=True),
sa.Column('accessed', sa.DateTime, nullable=False),
sa.Column('created', sa.DateTime, nullable=False),
sa.Column('data', sa.PickleType, nullable=False))
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