# taskflow.persistence.path_based

# Source code for taskflow.persistence.path_based

    # -*- coding: utf-8 -*-

    #    Copyright (C) 2015 Rackspace Hosting All Rights Reserved.
    #
    #    Licensed under the Apache License, Version 2.0 (the "License"); you may
    #    not use this file except in compliance with the License. You may obtain
    #    a copy of the License at
    #
    #         http://www.apache.org/licenses/LICENSE-2.0
    #
    #    Unless required by applicable law or agreed to in writing, software
    #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
    #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
    #    License for the specific language governing permissions and limitations
    #    under the License.

    import abc
    import six

    from taskflow import exceptions as exc
    from taskflow.persistence import base
    from taskflow.persistence import models

    @six.add_metaclass(abc.ABCMeta)
    class PathBasedBackend(base.Backend):
        """Base class for persistence backends that address data by path

        Subclasses of this backend write logbooks, flow details, and atom details
        to a provided base path in some filesystem-like storage. They will create
        and store those objects in three key directories (one for logbooks, one
        for flow details and one for atom details). They create those associated
        directories and then create files inside those directories that represent
        the contents of those objects for later reading and writing.
        """

        #: Default path used when none is provided.
        DEFAULT_PATH = None

        def __init__(self, conf):
            super(PathBasedBackend, self).__init__(conf)
            self._path = self._conf.get('path', None)
            if not self._path:
                self._path = self.DEFAULT_PATH

        @property
        def path(self):
            return self._path

    @six.add_metaclass(abc.ABCMeta)
    class PathBasedConnection(base.Connection):
        """Base class for path based backend connections."""

        def __init__(self, backend):
            self._backend = backend
            self._book_path = self._join_path(backend.path, "books")
            self._flow_path = self._join_path(backend.path, "flow_details")
            self._atom_path = self._join_path(backend.path, "atom_details")

        @staticmethod
        def _serialize(obj):
            if isinstance(obj, models.LogBook):
                return obj.to_dict(marshal_time=True)
            elif isinstance(obj, models.FlowDetail):
                return obj.to_dict()
            elif isinstance(obj, models.AtomDetail):
                return base._format_atom(obj)
            else:
                raise exc.StorageFailure("Invalid storage class %s" % type(obj))

        @staticmethod
        def _deserialize(cls, data):
            if issubclass(cls, models.LogBook):
                return cls.from_dict(data, unmarshal_time=True)
            elif issubclass(cls, models.FlowDetail):
                return cls.from_dict(data)
            elif issubclass(cls, models.AtomDetail):
                atom_class = models.atom_detail_class(data['type'])
                return atom_class.from_dict(data['atom'])
            else:
                raise exc.StorageFailure("Invalid storage class %s" % cls)

        @property
        def backend(self):
            return self._backend

        @property
        def book_path(self):
            return self._book_path

        @property
        def flow_path(self):
            return self._flow_path

        @property
        def atom_path(self):
            return self._atom_path

        @abc.abstractmethod
        def _join_path(self, *parts):
            """Accept path parts, and return a joined path"""

        @abc.abstractmethod
        def _get_item(self, path):
            """Fetch a single item from the backend"""

        @abc.abstractmethod
        def _set_item(self, path, value, transaction):
            """Write a single item to the backend"""

        @abc.abstractmethod
        def _del_tree(self, path, transaction):
            """Recursively deletes a folder from the backend."""

        @abc.abstractmethod
        def _get_children(self, path):
            """Get a list of child items of a path"""

        @abc.abstractmethod
        def _ensure_path(self, path):
            """Recursively ensure that a path (folder) in the backend exists"""

        @abc.abstractmethod
        def _create_link(self, src_path, dest_path, transaction):
            """Create a symlink-like link between two paths"""

        @abc.abstractmethod
        def _transaction(self):
            """Context manager that yields a transaction"""

        def _get_obj_path(self, obj):
            if isinstance(obj, models.LogBook):
                path = self.book_path
            elif isinstance(obj, models.FlowDetail):
                path = self.flow_path
            elif isinstance(obj, models.AtomDetail):
                path = self.atom_path
            else:
                raise exc.StorageFailure("Invalid storage class %s" % type(obj))
            return self._join_path(path, obj.uuid)

        def _update_object(self, obj, transaction, ignore_missing=False):
            path = self._get_obj_path(obj)
            try:
                item_data = self._get_item(path)
                existing_obj = self._deserialize(type(obj), item_data)
                obj = existing_obj.merge(obj)
            except exc.NotFound:
                if not ignore_missing:
                    raise
            self._set_item(path, self._serialize(obj), transaction)
            return obj

        def get_logbooks(self, lazy=False):
            for book_uuid in self._get_children(self.book_path):
                yield self.get_logbook(book_uuid, lazy=lazy)

        def get_logbook(self, book_uuid, lazy=False):
            book_path = self._join_path(self.book_path, book_uuid)
            book_data = self._get_item(book_path)
            book = self._deserialize(models.LogBook, book_data)
            if not lazy:
                for flow_details in self.get_flows_for_book(book_uuid):
                    book.add(flow_details)
            return book

        def save_logbook(self, book):
            book_path = self._get_obj_path(book)
            with self._transaction() as transaction:
                self._update_object(book, transaction, ignore_missing=True)
                for flow_details in book:
                    flow_path = self._get_obj_path(flow_details)
                    link_path = self._join_path(book_path, flow_details.uuid)
                    self._do_update_flow_details(flow_details, transaction,
                                                 ignore_missing=True)
                    self._create_link(flow_path, link_path, transaction)
            return book

        def get_flows_for_book(self, book_uuid, lazy=False):
            book_path = self._join_path(self.book_path, book_uuid)
            for flow_uuid in self._get_children(book_path):
                yield self.get_flow_details(flow_uuid, lazy)

        def get_flow_details(self, flow_uuid, lazy=False):
            flow_path = self._join_path(self.flow_path, flow_uuid)
            flow_data = self._get_item(flow_path)
            flow_details = self._deserialize(models.FlowDetail, flow_data)
            if not lazy:
                for atom_details in self.get_atoms_for_flow(flow_uuid):
                    flow_details.add(atom_details)
            return flow_details

        def _do_update_flow_details(self, flow_detail, transaction,
                                    ignore_missing=False):
            flow_path = self._get_obj_path(flow_detail)
            self._update_object(flow_detail, transaction,
                                ignore_missing=ignore_missing)
            for atom_details in flow_detail:
                atom_path = self._get_obj_path(atom_details)
                link_path = self._join_path(flow_path, atom_details.uuid)
                self._create_link(atom_path, link_path, transaction)
                self._update_object(atom_details, transaction, ignore_missing=True)
            return flow_detail

        def update_flow_details(self, flow_detail, ignore_missing=False):
            with self._transaction() as transaction:
                return self._do_update_flow_details(flow_detail, transaction,
                                                    ignore_missing=ignore_missing)

        def get_atoms_for_flow(self, flow_uuid):
            flow_path = self._join_path(self.flow_path, flow_uuid)
            for atom_uuid in self._get_children(flow_path):
                yield self.get_atom_details(atom_uuid)

        def get_atom_details(self, atom_uuid):
            atom_path = self._join_path(self.atom_path, atom_uuid)
            atom_data = self._get_item(atom_path)
            return self._deserialize(models.AtomDetail, atom_data)

        def update_atom_details(self, atom_detail, ignore_missing=False):
            with self._transaction() as transaction:
                return self._update_object(atom_detail, transaction,
                                           ignore_missing=ignore_missing)

        def _do_destroy_logbook(self, book_uuid, transaction):
            book_path = self._join_path(self.book_path, book_uuid)
            for flow_uuid in self._get_children(book_path):
                flow_path = self._join_path(self.flow_path, flow_uuid)
                for atom_uuid in self._get_children(flow_path):
                    atom_path = self._join_path(self.atom_path, atom_uuid)
                    self._del_tree(atom_path, transaction)
                self._del_tree(flow_path, transaction)
            self._del_tree(book_path, transaction)

        def destroy_logbook(self, book_uuid):
            with self._transaction() as transaction:
                return self._do_destroy_logbook(book_uuid, transaction)

        def clear_all(self):
            with self._transaction() as transaction:
                for path in (self.book_path, self.flow_path, self.atom_path):
                    self._del_tree(path, transaction)

        def upgrade(self):
            for path in (self.book_path, self.flow_path, self.atom_path):
                self._ensure_path(path)

        def close(self):
            pass

this page last updated: 2020-04-10 14:06:26

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