[source] implement storages right in the source rather than in hooks
The problem is that Storage objects will most probably change entity's
dictionary so that values are correctly set before the source's
corresponding method (e.g. entity_added()) is called.
For instance, the BFSFileStorage will change the original binary
data and replace it with the destination file path in order to store
the file path in the database. This change must be local
to the source in order not to impact other hooks or attribute access
during the transaction, the whole idea being that the same
application code should work exactly the same whether or not a
BFSStorage is used or not.
"""custom storages for the system source"""
from os import unlink, path as osp
from cubicweb import Binary
from cubicweb.server.hook import Operation
def set_attribute_storage(repo, etype, attr, storage):
repo.system_source.set_storage(etype, attr, storage)
def unset_attribute_storage(repo, etype, attr):
repo.system_source.unset_storage(etype, attr)
class Storage(object):
"""abstract storage"""
def sqlgen_callback(self, generator, relation, linkedvar):
"""sql generator callback when some attribute with a custom storage is
accessed
"""
raise NotImplementedError()
def entity_added(self, entity, attr):
"""an entity using this storage for attr has been added"""
raise NotImplementedError()
def entity_updated(self, entity, attr):
"""an entity using this storage for attr has been updatded"""
raise NotImplementedError()
def entity_deleted(self, entity, attr):
"""an entity using this storage for attr has been deleted"""
raise NotImplementedError()
# TODO
# * make it configurable without code
# * better file path attribution
# * handle backup/restore
class BytesFileSystemStorage(Storage):
"""store Bytes attribute value on the file system"""
def __init__(self, defaultdir):
self.default_directory = defaultdir
def sqlgen_callback(self, generator, linkedvar, relation):
"""sql generator callback when some attribute with a custom storage is
accessed
"""
linkedvar.accept(generator)
return '_fsopen(%s.cw_%s)' % (
linkedvar._q_sql.split('.', 1)[0], # table name
relation.r_type) # attribute name
def entity_added(self, entity, attr):
"""an entity using this storage for attr has been added"""
if not entity._cw.transaction_data.get('fs_importing'):
try:
value = entity.pop(attr)
except KeyError:
pass
else:
fpath = self.new_fs_path(entity, attr)
# bytes storage used to store file's path
entity[attr] = Binary(fpath)
file(fpath, 'w').write(value.getvalue())
AddFileOp(entity._cw, filepath=fpath)
# else entity[attr] is expected to be an already existant file path
def entity_updated(self, entity, attr):
"""an entity using this storage for attr has been updatded"""
try:
value = entity.pop(attr)
except KeyError:
pass
else:
fpath = self.current_fs_path(entity, attr)
UpdateFileOp(entity._cw, filepath=fpath, filedata=value.getvalue())
def entity_deleted(self, entity, attr):
"""an entity using this storage for attr has been deleted"""
DeleteFileOp(entity._cw, filepath=self.current_fs_path(entity, attr))
def new_fs_path(self, entity, attr):
fspath = osp.join(self.default_directory, '%s_%s' % (entity.eid, attr))
while osp.exists(fspath):
fspath = '_' + fspath
return fspath
def current_fs_path(self, entity, attr):
sysource = entity._cw.pool.source('system')
cu = sysource.doexec(entity._cw,
'SELECT cw_%s FROM cw_%s WHERE cw_eid=%s' % (
attr, entity.__regid__, entity.eid))
return sysource._process_value(cu.fetchone()[0], [None, dbmod.BINARY],
binarywrap=str)
class AddFileOp(Operation):
def rollback_event(self):
try:
unlink(self.filepath)
except:
pass
class DeleteFileOp(Operation):
def commit_event(self):
try:
unlink(self.filepath)
except:
pass
class UpdateFileOp(Operation):
def precommit_event(self):
try:
file(self.filepath, 'w').write(self.filedata)
except Exception, ex:
self.exception(str(ex))