# taskflow.engines.action_engine.traversal

# Source code for taskflow.engines.action_engine.traversal

    #    Copyright (C) 2015 Yahoo! Inc. 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 collections
    import enum

    from taskflow.engines.action_engine import compiler as co

    class Direction(enum.Enum):
        """Traversal direction enum."""

        #: Go through successors.
        FORWARD = 1

        #: Go through predecessors.
        BACKWARD = 2

    def _extract_connectors(execution_graph, starting_node, direction,
                            through_flows=True, through_retries=True,
                            through_tasks=True):
        if direction == Direction.FORWARD:
            connected_iter = execution_graph.successors
        else:
            connected_iter = execution_graph.predecessors
        connected_to_functors = {}
        if through_flows:
            connected_to_functors[co.FLOW] = connected_iter
            connected_to_functors[co.FLOW_END] = connected_iter
        if through_retries:
            connected_to_functors[co.RETRY] = connected_iter
        if through_tasks:
            connected_to_functors[co.TASK] = connected_iter
        return connected_iter(starting_node), connected_to_functors

    def breadth_first_iterate(execution_graph, starting_node, direction,
                              through_flows=True, through_retries=True,
                              through_tasks=True):
        """Iterates connected nodes in execution graph (from starting node).

        Does so in a breadth first manner.

        Jumps over nodes with ``noop`` attribute (does not yield them back).
        """
        initial_nodes_iter, connected_to_functors = _extract_connectors(
            execution_graph, starting_node, direction,
            through_flows=through_flows, through_retries=through_retries,
            through_tasks=through_tasks)
        q = collections.deque(initial_nodes_iter)
        while q:
            node = q.popleft()
            node_attrs = execution_graph.nodes[node]
            if not node_attrs.get('noop'):
                yield node
            try:
                node_kind = node_attrs['kind']
                connected_to_functor = connected_to_functors[node_kind]
            except KeyError:
                pass
            else:
                q.extend(connected_to_functor(node))

    def depth_first_iterate(execution_graph, starting_node, direction,
                            through_flows=True, through_retries=True,
                            through_tasks=True):
        """Iterates connected nodes in execution graph (from starting node).

        Does so in a depth first manner.

        Jumps over nodes with ``noop`` attribute (does not yield them back).
        """
        initial_nodes_iter, connected_to_functors = _extract_connectors(
            execution_graph, starting_node, direction,
            through_flows=through_flows, through_retries=through_retries,
            through_tasks=through_tasks)
        stack = list(initial_nodes_iter)
        while stack:
            node = stack.pop()
            node_attrs = execution_graph.nodes[node]
            if not node_attrs.get('noop'):
                yield node
            try:
                node_kind = node_attrs['kind']
                connected_to_functor = connected_to_functors[node_kind]
            except KeyError:
                pass
            else:
                stack.extend(connected_to_functor(node))

    def depth_first_reverse_iterate(node, start_from_idx=-1):
        """Iterates connected (in reverse) **tree** nodes (from starting node).

        Jumps through nodes with ``noop`` attribute (does not yield them back).
        """
        # Always go left to right, since right to left is the pattern order
        # and we want to go backwards and not forwards through that ordering...
        if start_from_idx == -1:
            # All of them...
            children_iter = node.reverse_iter()
        else:
            children_iter = reversed(node[0:start_from_idx])
        for child in children_iter:
            if child.metadata.get('noop'):
                # Jump through these...
                for grand_child in child.dfs_iter(right_to_left=False):
                    if grand_child.metadata['kind'] in co.ATOMS:
                        yield grand_child.item
            else:
                yield child.item

this page last updated: 2026-01-23 20:25:53

Except where otherwise noted, this document is licensed under Creative Commons Attribution 3.0 License. See all OpenStack Legal Documents.

found an error? report a bug