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
pool = None
types = None
class DatabaseNamespaceManager(OpenResourceNamespaceManager):
metadatas = SyncDict()
tables = SyncDict()
@classmethod
def _init_dependencies(cls):
global sa, pool, types
if sa is not None:
return
try:
import sqlalchemy as sa
import sqlalchemy.pool as pool
from sqlalchemy import types
except ImportError:
raise InvalidCacheBackendError("Database cache backend requires "
"the 'sqlalchemy' library")
def __init__(self, namespace, url=None, sa_opts=None, optimistic=False,
table_name='beaker_cache', data_dir=None, lock_dir=None,
**params):
"""Creates a database namespace manager
``url``
SQLAlchemy compliant db url
``sa_opts``
A dictionary of SQLAlchemy keyword options to initialize the engine
with.
``optimistic``
Use optimistic session locking, note that this will result in an
additional select when updating a cache value to compare version
numbers.
``table_name``
The table name to use in the database for the cache.
"""
OpenResourceNamespaceManager.__init__(self, namespace)
if sa_opts is None:
sa_opts = params
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)
# Check to see if the table's been created before
url = url or sa_opts['sa.url']
table_key = url + table_name
def make_cache():
# Check to see if we have a connection pool open already
meta_key = url + table_name
def make_meta():
# SQLAlchemy pops the url, this ensures it sticks around
# later
sa_opts['sa.url'] = url
engine = sa.engine_from_config(sa_opts, 'sa.')
meta = sa.MetaData()
meta.bind = engine
return meta
meta = DatabaseNamespaceManager.metadatas.get(meta_key, make_meta)
# Create the table object and cache it now
cache = sa.Table(table_name, meta,
sa.Column('id', types.Integer, primary_key=True),
sa.Column('namespace', types.String(255), nullable=False),
sa.Column('accessed', types.DateTime, nullable=False),
sa.Column('created', types.DateTime, nullable=False),
sa.Column('data', types.PickleType, nullable=False),
sa.UniqueConstraint('namespace')
)
cache.create(checkfirst=True)
return cache
self.hash = {}
self._is_new = False
self.loaded = False
self.cache = DatabaseNamespaceManager.tables.get(table_key, make_cache)
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 we already loaded the data, don't bother loading it again
if self.loaded:
self.flags = flags
return
cache = self.cache
result = sa.select([cache.c.data],
cache.c.namespace==self.namespace
).execute().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'):
cache = self.cache
if self._is_new:
cache.insert().execute(namespace=self.namespace, data=self.hash,
accessed=datetime.now(),
created=datetime.now())
self._is_new = False
else:
cache.update(cache.c.namespace==self.namespace).execute(
data=self.hash, accessed=datetime.now())
self.flags = None
def do_remove(self):
cache = self.cache
cache.delete(cache.c.namespace==self.namespace).execute()
self.hash = {}
# We can retain the fact that we did a load attempt, but since the
# file is gone this will be a new namespace should it be saved.
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 DatabaseContainer(Container):
namespace_manager = DatabaseNamespaceManager