247 lines
7.8 KiB
Python
247 lines
7.8 KiB
Python
#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import collections
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import itertools
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from six.moves import xrange
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from heat.common import exception
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from heat.openstack.common.gettextutils import _
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class CircularDependencyException(exception.HeatException):
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msg_fmt = _("Circular Dependency Found: %(cycle)s")
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class Node(object):
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'''A node in a dependency graph.'''
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def __init__(self, requires=None, required_by=None):
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'''
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Initialise the node, optionally with a set of keys this node
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requires and/or a set of keys that this node is required by.
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'''
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self.require = requires and requires.copy() or set()
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self.satisfy = required_by and required_by.copy() or set()
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def copy(self):
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'''Return a copy of the node.'''
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return Node(self.require, self.satisfy)
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def reverse_copy(self):
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'''Return a copy of the node with the edge directions reversed.'''
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return Node(self.satisfy, self.require)
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def required_by(self, source=None):
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'''
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List the keys that require this node, and optionally add a
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new one.
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'''
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if source is not None:
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self.satisfy.add(source)
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return iter(self.satisfy)
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def requires(self, target):
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'''Add a key that this node requires.'''
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self.require.add(target)
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def __isub__(self, target):
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'''Remove a key that this node requires.'''
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self.require.remove(target)
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return self
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def __nonzero__(self):
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'''Return True if this node is not a leaf (it requires other nodes).'''
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return bool(self.require)
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def stem(self):
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'''Return True if this node is a stem (required by nothing).'''
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return not bool(self.satisfy)
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def disjoint(self):
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'''Return True if this node is both a leaf and a stem.'''
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return (not self) and self.stem()
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def __len__(self):
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'''Count the number of keys required by this node.'''
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return len(self.require)
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def __iter__(self):
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'''Iterate over the keys required by this node.'''
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return iter(self.require)
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def __str__(self):
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'''Return a human-readable string representation of the node.'''
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return '{%s}' % ', '.join(str(n) for n in self)
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def __repr__(self):
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'''Return a string representation of the node.'''
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return repr(self.require)
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class Graph(collections.defaultdict):
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'''A mutable mapping of objects to nodes in a dependency graph.'''
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def __init__(self, *args):
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super(Graph, self).__init__(Node, *args)
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def map(self, func):
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'''
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Return a dictionary derived from mapping the supplied function onto
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each node in the graph.
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'''
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return dict((k, func(n)) for k, n in self.items())
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def copy(self):
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'''Return a copy of the graph.'''
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return Graph(self.map(lambda n: n.copy()))
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def reverse_copy(self):
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'''Return a copy of the graph with the edges reversed.'''
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return Graph(self.map(lambda n: n.reverse_copy()))
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def edges(self):
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'''Return an iterator over all of the edges in the graph.'''
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def outgoing_edges(rqr, node):
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if node.disjoint():
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yield (rqr, None)
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else:
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for rqd in node:
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yield (rqr, rqd)
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return itertools.chain.from_iterable(outgoing_edges(*i)
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for i in self.iteritems())
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def __delitem__(self, key):
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'''Delete the node given by the specified key from the graph.'''
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node = self[key]
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for src in node.required_by():
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src_node = self[src]
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if key in src_node:
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src_node -= key
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return super(Graph, self).__delitem__(key)
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def __str__(self):
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'''Convert the graph to a human-readable string.'''
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pairs = ('%s: %s' % (str(k), str(v)) for k, v in self.iteritems())
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return '{%s}' % ', '.join(pairs)
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@staticmethod
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def toposort(graph):
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'''
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Return a topologically sorted iterator over a dependency graph.
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This is a destructive operation for the graph.
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'''
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for iteration in xrange(len(graph)):
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for key, node in graph.iteritems():
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if not node:
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yield key
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del graph[key]
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break
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else:
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# There are nodes remaining, but none without
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# dependencies: a cycle
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raise CircularDependencyException(cycle=str(graph))
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class Dependencies(object):
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'''Helper class for calculating a dependency graph.'''
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def __init__(self, edges=[]):
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'''
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Initialise, optionally with a list of edges, in the form of
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(requirer, required) tuples.
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'''
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self._graph = Graph()
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for e in edges:
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self += e
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def __iadd__(self, edge):
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'''Add another edge, in the form of a (requirer, required) tuple.'''
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requirer, required = edge
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if required is None:
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# Just ensure the node is created by accessing the defaultdict
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self._graph[requirer]
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else:
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self._graph[required].required_by(requirer)
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self._graph[requirer].requires(required)
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return self
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def required_by(self, last):
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'''
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List the keys that require the specified node.
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'''
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if last not in self._graph:
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raise KeyError
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return self._graph[last].required_by()
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def __getitem__(self, last):
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'''
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Return a partial dependency graph consisting of the specified node and
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all those that require it only.
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'''
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if last not in self._graph:
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raise KeyError
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def get_edges(key):
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def requirer_edges(rqr):
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# Concatenate the dependency on the current node with the
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# recursive generated list
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return itertools.chain([(rqr, key)], get_edges(rqr))
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# Get the edge list for each node that requires the current node
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edge_lists = itertools.imap(requirer_edges,
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self._graph[key].required_by())
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# Combine the lists into one long list
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return itertools.chain.from_iterable(edge_lists)
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if self._graph[last].stem():
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# Nothing requires this, so just add the node itself
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edges = [(last, None)]
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else:
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edges = get_edges(last)
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return Dependencies(edges)
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def __str__(self):
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'''
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Return a human-readable string representation of the dependency graph
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'''
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return str(self._graph)
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def __repr__(self):
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'''Return a string representation of the object.'''
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edge_reprs = (repr(e) for e in self._graph.edges())
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return 'Dependencies([%s])' % ', '.join(edge_reprs)
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def graph(self, reverse=False):
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'''Return a copy of the underlying dependency graph.'''
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if reverse:
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return self._graph.reverse_copy()
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else:
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return self._graph.copy()
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def __iter__(self):
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'''Return a topologically sorted iterator'''
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return Graph.toposort(self.graph())
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def __reversed__(self):
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'''Return a reverse topologically sorted iterator'''
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return Graph.toposort(self.graph(reverse=True))
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