#
# 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 itertools
from heat.common import exception
[docs]
class Node(object):
"""A node in a dependency graph."""
__slots__ = ('require', 'satisfy')
def __init__(self, requires=None, required_by=None):
"""Initialisation of the node.
Initialise the node, optionally with a set of keys this node
requires and/or a set of keys that this node is required by.
"""
self.require = requires and requires.copy() or set()
self.satisfy = required_by and required_by.copy() or set()
[docs]
def copy(self):
"""Return a copy of the node."""
return Node(self.require, self.satisfy)
[docs]
def reverse_copy(self):
"""Return a copy of the node with the edge directions reversed."""
return Node(self.satisfy, self.require)
[docs]
def required_by(self, source=None):
"""List the keys that require this node, and optionally add new one."""
if source is not None:
self.satisfy.add(source)
return iter(self.satisfy)
[docs]
def requires(self, target=None):
"""List the keys that this node requires, and optionally add a new one.
"""
if target is not None:
self.require.add(target)
return iter(self.require)
def __isub__(self, target):
"""Remove a key that this node requires."""
self.require.remove(target)
return self
def __nonzero__(self):
"""Return True if this node is not a leaf (it requires other nodes)."""
return bool(self.require)
def __bool__(self):
"""Return True if this node is not a leaf (it requires other nodes)."""
return self.__nonzero__()
[docs]
def stem(self):
"""Return True if this node is a stem (required by nothing)."""
return not bool(self.satisfy)
[docs]
def disjoint(self):
"""Return True if this node is both a leaf and a stem."""
return (not self) and self.stem()
def __len__(self):
"""Count the number of keys required by this node."""
return len(self.require)
def __iter__(self):
"""Iterate over the keys required by this node."""
return iter(self.require)
def __str__(self):
"""Return a human-readable string representation of the node."""
text = '{%s}' % ', '.join(str(n) for n in self)
return str(text)
def __repr__(self):
"""Return a string representation of the node."""
return repr(self.require)
[docs]
class Graph(collections.defaultdict):
"""A mutable mapping of objects to nodes in a dependency graph."""
def __init__(self, *args):
super(Graph, self).__init__(Node, *args)
[docs]
def map(self, func):
"""Map the supplied function onto each node in the graph.
Return a dictionary derived from mapping the supplied function onto
each node in the graph.
"""
return dict((k, func(n)) for k, n in self.items())
[docs]
def copy(self):
"""Return a copy of the graph."""
return Graph(self.map(lambda n: n.copy()))
[docs]
def reverse_copy(self):
"""Return a copy of the graph with the edges reversed."""
return Graph(self.map(lambda n: n.reverse_copy()))
[docs]
def edges(self):
"""Return an iterator over all of the edges in the graph."""
def outgoing_edges(rqr, node):
if node.disjoint():
yield (rqr, None)
else:
for rqd in node:
yield (rqr, rqd)
return itertools.chain.from_iterable(outgoing_edges(*i)
for i in self.items())
def __delitem__(self, key):
"""Delete the node given by the specified key from the graph."""
node = self[key]
for src in node.required_by():
src_node = self[src]
if key in src_node:
src_node -= key
return super(Graph, self).__delitem__(key)
def __str__(self):
"""Convert the graph to a human-readable string."""
pairs = ('%s: %s' % (str(k), str(v))
for k, v in self.items())
text = '{%s}' % ', '.join(pairs)
return str(text)
[docs]
@staticmethod
def toposort(graph):
"""Return a topologically sorted iterator over a dependency graph.
This is a destructive operation for the graph.
"""
for iteration in range(len(graph)):
for key, node in graph.items():
if not node:
yield key
del graph[key]
break
else:
# There are nodes remaining, but none without
# dependencies: a cycle
raise exception.CircularDependencyException(cycle=str(graph))
[docs]
class Dependencies(object):
"""Helper class for calculating a dependency graph."""
def __init__(self, edges=None):
"""Initialise, optionally with a list of edges.
Each edge takes the form of a (requirer, required) tuple.
"""
edges = edges or []
self._graph = Graph()
for e in edges:
self += e
def __iadd__(self, edge):
"""Add another edge, in the form of a (requirer, required) tuple."""
requirer, required = edge
if required is None:
# Just ensure the node is created by accessing the defaultdict
self._graph[requirer]
else:
self._graph[required].required_by(requirer)
self._graph[requirer].requires(required)
return self
[docs]
def required_by(self, last):
"""List the keys that require the specified node."""
if last not in self._graph:
raise KeyError
return self._graph[last].required_by()
[docs]
def requires(self, source):
"""List the keys that the specified node requires."""
if source not in self._graph:
raise KeyError
return self._graph[source].requires()
def __getitem__(self, last):
"""Return a partial dependency graph starting with the specified node.
Return a subset of the dependency graph consisting of the specified
node and all those that require it only.
"""
if last not in self._graph:
raise KeyError
def get_edges(key):
def requirer_edges(rqr):
# Concatenate the dependency on the current node with the
# recursive generated list
return itertools.chain([(rqr, key)], get_edges(rqr))
# Get the edge list for each node that requires the current node
edge_lists = map(requirer_edges,
self._graph[key].required_by())
# Combine the lists into one long list
return itertools.chain.from_iterable(edge_lists)
if self._graph[last].stem():
# Nothing requires this, so just add the node itself
edges = [(last, None)]
else:
edges = get_edges(last)
return Dependencies(edges)
[docs]
def leaves(self):
"""Return an iterator over all of the leaf nodes in the graph."""
return (requirer for requirer, required in self._graph.items()
if not required)
[docs]
def roots(self):
"""Return an iterator over all of the root nodes in the graph."""
return (requirer for requirer, required in self.graph(
reverse=True).items() if not required)
[docs]
def translate(self, transform):
"""Translate all of the nodes using a transform function.
Returns a new Dependencies object.
"""
def transform_key(key):
return transform(key) if key is not None else None
edges = self._graph.edges()
return type(self)(tuple(map(transform_key, e)) for e in edges)
def __str__(self):
"""Return a human-readable string repr of the dependency graph."""
return str(self._graph)
def __repr__(self):
"""Return a consistent string representation of the object."""
edge_reprs = sorted(repr(e) for e in self._graph.edges())
text = 'Dependencies([%s])' % ', '.join(edge_reprs)
return text
[docs]
def graph(self, reverse=False):
"""Return a copy of the underlying dependency graph."""
if reverse:
return self._graph.reverse_copy()
else:
return self._graph.copy()
def __iter__(self):
"""Return a topologically sorted iterator."""
return Graph.toposort(self.graph())
def __reversed__(self):
"""Return a reverse topologically sorted iterator."""
return Graph.toposort(self.graph(reverse=True))
