storages.py 11.5 KB
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# copyright 2003-2013 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
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# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb is free software: you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option)
# any later version.
#
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# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
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"""custom storages for the system source"""
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import os
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import sys
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from os import unlink, path as osp
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from contextlib import contextmanager
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import tempfile
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from six import PY2, PY3, text_type, binary_type

from logilab.common import nullobject

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from yams.schema import role_name

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from cubicweb import Binary, ValidationError
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from cubicweb.server import hook
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from cubicweb.server.edition import EditedEntity
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def set_attribute_storage(repo, etype, attr, storage):
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    repo.system_source.set_storage(etype, attr, storage)
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def unset_attribute_storage(repo, etype, attr):
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    repo.system_source.unset_storage(etype, attr)
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class Storage(object):
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    """abstract storage

    * If `source_callback` is true (by default), the callback will be run during
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      query result process of fetched attribute's value and should have the
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      following prototype::

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        callback(self, source, cnx, value)
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      where `value` is the value actually stored in the backend. None values
      will be skipped (eg callback won't be called).

    * if `source_callback` is false, the callback will be run during sql
      generation when some attribute with a custom storage is accessed and
      should have the following prototype::

        callback(self, generator, relation, linkedvar)

      where `generator` is the sql generator, `relation` the current rql syntax
      tree relation and linkedvar the principal syntax tree variable holding the
      attribute.
    """
    is_source_callback = True

    def callback(self, *args):
        """see docstring for prototype, which vary according to is_source_callback
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        """
        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()
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    def migrate_entity(self, entity, attribute):
        """migrate an entity attribute to the storage"""
        raise NotImplementedError()
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# TODO
# * make it configurable without code
# * better file path attribution
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# * handle backup/restore
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def uniquify_path(dirpath, basename):
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    """return a file descriptor and unique file name for `basename` in `dirpath`
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    """
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    path = basename.replace(osp.sep, '-')
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    base, ext = osp.splitext(path)
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    return tempfile.mkstemp(prefix=base, suffix=ext, dir=dirpath)
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@contextmanager
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def fsimport(cnx):
    present = 'fs_importing' in cnx.transaction_data
    old_value = cnx.transaction_data.get('fs_importing')
    cnx.transaction_data['fs_importing'] = True
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    yield
    if present:
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        cnx.transaction_data['fs_importing'] = old_value
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    else:
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        del cnx.transaction_data['fs_importing']
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_marker = nullobject()


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class BytesFileSystemStorage(Storage):
    """store Bytes attribute value on the file system"""
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    def __init__(self, defaultdir, fsencoding=_marker, wmode=0o444):
        if PY3:
            if not isinstance(defaultdir, text_type):
                raise TypeError('defaultdir must be a unicode object in python 3')
            if fsencoding is not _marker:
                raise ValueError('fsencoding is no longer supported in python 3')
        else:
            self.fsencoding = fsencoding or 'utf-8'
            if isinstance(defaultdir, text_type):
                defaultdir = defaultdir.encode(fsencoding)
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        self.default_directory = defaultdir
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        # extra umask to use when creating file
        # 0444 as in "only allow read bit in permission"
        self._wmode = wmode

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    def _writecontent(self, fd, binary):
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        """write the content of a binary in readonly file

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        As the bfss never alters an existing file it does not prevent it from
        working as intended. This is a better safe than sorry approach.
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        """
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        os.fchmod(fd, self._wmode)
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        fileobj = os.fdopen(fd, 'wb')
        binary.to_file(fileobj)
        fileobj.close()

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    def callback(self, source, cnx, value):
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        """sql generator callback when some attribute with a custom storage is
        accessed
        """
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        fpath = source.binary_to_str(value)
        try:
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            return Binary.from_file(fpath)
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        except EnvironmentError as ex:
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            source.critical("can't open %s: %s", value, ex)
            return None
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    def entity_added(self, entity, attr):
        """an entity using this storage for attr has been added"""
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        if entity._cw.transaction_data.get('fs_importing'):
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            binary = Binary.from_file(entity.cw_edited[attr].getvalue())
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        else:
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            binary = entity.cw_edited.pop(attr)
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            fd, fpath = self.new_fs_path(entity, attr)
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            # bytes storage used to store file's path
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            binary_obj = Binary(fpath if PY2 else fpath.encode('utf-8'))
            entity.cw_edited.edited_attribute(attr, binary_obj)
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            self._writecontent(fd, binary)
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            AddFileOp.get_instance(entity._cw).add_data(fpath)
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        return binary
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    def entity_updated(self, entity, attr):
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        """an entity using this storage for attr has been updated"""
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        # get the name of the previous file containing the value
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        oldpath = self.current_fs_path(entity, attr)
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        if entity._cw.transaction_data.get('fs_importing'):
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            # If we are importing from the filesystem, the file already exists.
            # We do not need to create it but we need to fetch the content of
            # the file as the actual content of the attribute
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            fpath = entity.cw_edited[attr].getvalue()
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            assert fpath is not None
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            binary = Binary.from_file(fpath)
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        else:
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            # We must store the content of the attributes
            # into a file to stay consistent with the behaviour of entity_add.
            # Moreover, the BytesFileSystemStorage expects to be able to
            # retrieve the current value of the attribute at anytime by reading
            # the file on disk. To be able to rollback things, use a new file
            # and keep the old one that will be removed on commit if everything
            # went ok.
            #
            # fetch the current attribute value in memory
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            binary = entity.cw_edited.pop(attr)
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            if binary is None:
                fpath = None
            else:
                # Get filename for it
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                fd, fpath = self.new_fs_path(entity, attr)
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                # write attribute value on disk
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                self._writecontent(fd, binary)
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                # Mark the new file as added during the transaction.
                # The file will be removed on rollback
                AddFileOp.get_instance(entity._cw).add_data(fpath)
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            # reinstall poped value
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            if fpath is None:
                entity.cw_edited.edited_attribute(attr, None)
            else:
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                # register the new location for the file.
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                binary_obj = Binary(fpath if PY2 else fpath.encode('utf-8'))
                entity.cw_edited.edited_attribute(attr, binary_obj)
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        if oldpath is not None and oldpath != fpath:
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            # Mark the old file as useless so the file will be removed at
            # commit.
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            DeleteFileOp.get_instance(entity._cw).add_data(oldpath)
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        return binary
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    def entity_deleted(self, entity, attr):
        """an entity using this storage for attr has been deleted"""
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        fpath = self.current_fs_path(entity, attr)
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        if fpath is not None:
            DeleteFileOp.get_instance(entity._cw).add_data(fpath)
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    def new_fs_path(self, entity, attr):
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        # We try to get some hint about how to name the file using attribute's
        # name metadata, so we use the real file name and extension when
        # available. Keeping the extension is useful for example in the case of
        # PIL processing that use filename extension to detect content-type, as
        # well as providing more understandable file names on the fs.
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        if PY2:
            attr = attr.encode('ascii')
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        basename = [str(entity.eid), attr]
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        name = entity.cw_attr_metadata(attr, 'name')
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        if name is not None:
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            basename.append(name.encode(self.fsencoding) if PY2 else name)
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        fd, fspath = uniquify_path(self.default_directory,
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                               '_'.join(basename))
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        if fspath is None:
            msg = entity._cw._('failed to uniquify path (%s, %s)') % (
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                self.default_directory, '_'.join(basename))
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            raise ValidationError(entity.eid, {role_name(attr, 'subject'): msg})
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        assert isinstance(fspath, str)  # bytes on py2, unicode on py3
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        return fd, fspath
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    def current_fs_path(self, entity, attr):
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        """return the current fs_path of the attribute, or None is the attr is
        not stored yet.
        """
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        sysource = entity._cw.repo.system_source
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        cu = sysource.doexec(entity._cw,
                             'SELECT cw_%s FROM cw_%s WHERE cw_eid=%s' % (
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                             attr, entity.cw_etype, entity.eid))
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        rawvalue = cu.fetchone()[0]
        if rawvalue is None: # no previous value
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            return None
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        fspath = sysource._process_value(rawvalue, cu.description[0],
                                         binarywrap=binary_type)
        if PY3:
            fspath = fspath.decode('utf-8')
        assert isinstance(fspath, str)  # bytes on py2, unicode on py3
        return fspath
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    def migrate_entity(self, entity, attribute):
        """migrate an entity attribute to the storage"""
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        entity.cw_edited = EditedEntity(entity, **entity.cw_attr_cache)
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        self.entity_added(entity, attribute)
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        cnx = entity._cw
        source = cnx.repo.system_source
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        attrs = source.preprocess_entity(entity)
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        sql = source.sqlgen.update('cw_' + entity.cw_etype, attrs,
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                                   ['cw_eid'])
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        source.doexec(cnx, sql, attrs)
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        entity.cw_edited = None
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class AddFileOp(hook.DataOperationMixIn, hook.Operation):
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    def rollback_event(self):
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        for filepath in self.get_data():
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            assert isinstance(filepath, str)  # bytes on py2, unicode on py3
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            try:
                unlink(filepath)
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            except Exception as ex:
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                self.error("can't remove %s: %s" % (filepath, ex))
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class DeleteFileOp(hook.DataOperationMixIn, hook.Operation):
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    def postcommit_event(self):
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        for filepath in self.get_data():
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            assert isinstance(filepath, str)  # bytes on py2, unicode on py3
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            try:
                unlink(filepath)
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            except Exception as ex:
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                self.error("can't remove %s: %s" % (filepath, ex))