deb-heat/heat/engine/dependencies.py
Jens Rosenboom a99fe6a760 Make import of oslo libraries namespaceless
See https://blueprints.launchpad.net/oslo-incubator/+spec/drop-namespace-packages

Closes-Bug: 1423174
Change-Id: I48680ce6e7ce91005c147ab4388203946171d433
2015-02-18 22:54:10 +01:00

270 lines
8.7 KiB
Python

#
# 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 oslo_utils import encodeutils
import six
from heat.common import exception
from heat.common.i18n import _
class CircularDependencyException(exception.HeatException):
msg_fmt = _("Circular Dependency Found: %(cycle)s")
class Node(object):
'''A node in a dependency graph.'''
def __init__(self, requires=None, required_by=None):
'''
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()
def copy(self):
'''Return a copy of the node.'''
return Node(self.require, self.satisfy)
def reverse_copy(self):
'''Return a copy of the node with the edge directions reversed.'''
return Node(self.satisfy, self.require)
def required_by(self, source=None):
'''
List the keys that require this node, and optionally add a
new one.
'''
if source is not None:
self.satisfy.add(source)
return iter(self.satisfy)
def requires(self, target):
'''Add a key that this node requires.'''
self.require.add(target)
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 stem(self):
'''Return True if this node is a stem (required by nothing).'''
return not bool(self.satisfy)
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 encodeutils.safe_encode(text)
def __unicode__(self):
'''Return a human-readable string representation of the node.'''
text = '{%s}' % ', '.join(six.text_type(n) for n in self)
return encodeutils.safe_decode(text)
def __repr__(self):
'''Return a string representation of the node.'''
return repr(self.require)
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)
def map(self, func):
'''
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())
def copy(self):
'''Return a copy of the graph.'''
return Graph(self.map(lambda n: n.copy()))
def reverse_copy(self):
'''Return a copy of the graph with the edges reversed.'''
return Graph(self.map(lambda n: n.reverse_copy()))
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 six.iteritems(self))
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 six.iteritems(self))
text = '{%s}' % ', '.join(pairs)
return encodeutils.safe_encode(text)
def __unicode__(self):
'''Convert the graph to a human-readable string.'''
pairs = ('%s: %s' % (six.text_type(k), six.text_type(v))
for k, v in six.iteritems(self))
text = '{%s}' % ', '.join(pairs)
return encodeutils.safe_decode(text)
@staticmethod
def toposort(graph):
'''
Return a topologically sorted iterator over a dependency graph.
This is a destructive operation for the graph.
'''
for iteration in six.moves.xrange(len(graph)):
for key, node in six.iteritems(graph):
if not node:
yield key
del graph[key]
break
else:
# There are nodes remaining, but none without
# dependencies: a cycle
raise CircularDependencyException(cycle=six.text_type(graph))
class Dependencies(object):
'''Helper class for calculating a dependency graph.'''
def __init__(self, edges=None):
'''
Initialise, optionally with a list of edges, in the form of
(requirer, required) tuples.
'''
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
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()
def __getitem__(self, last):
'''
Return a partial 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 = itertools.imap(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)
def __str__(self):
'''
Return a human-readable string representation of the dependency graph
'''
return str(self._graph)
def __unicode__(self):
'''
Return a human-readable string representation of the dependency graph
'''
return six.text_type(self._graph)
def __repr__(self):
'''Return a string representation of the object.'''
edge_reprs = (repr(e) for e in self._graph.edges())
text = 'Dependencies([%s])' % ', '.join(edge_reprs)
return encodeutils.safe_encode(text)
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))