c253b38e21
Moves the exception from inside the engine code to the common code so that we can use it in the API fault middleware. Change-Id: I017b95153c358829501f6a5740918cdb005fb32f
278 lines
9.1 KiB
Python
278 lines
9.1 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 heat.common import exception
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class Node(object):
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"""A node in a dependency graph."""
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__slots__ = ('require', 'satisfy')
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def __init__(self, requires=None, required_by=None):
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"""Initialisation of the node.
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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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"""List the keys that require this node, and optionally add new one."""
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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=None):
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"""List the keys that this node requires, and optionally add a new one.
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"""
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if target is not None:
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self.require.add(target)
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return iter(self.require)
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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 __bool__(self):
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"""Return True if this node is not a leaf (it requires other nodes)."""
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return self.__nonzero__()
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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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text = '{%s}' % ', '.join(str(n) for n in self)
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return str(text)
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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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"""Map the supplied function onto each node in the graph.
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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.items())
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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))
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for k, v in self.items())
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text = '{%s}' % ', '.join(pairs)
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return str(text)
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@staticmethod
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def toposort(graph):
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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 range(len(graph)):
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for key, node in graph.items():
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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 exception.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=None):
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"""Initialise, optionally with a list of edges.
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Each edge takes the form of a (requirer, required) tuple.
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"""
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edges = edges or []
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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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"""List the keys that require the specified node."""
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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 requires(self, source):
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"""List the keys that the specified node requires."""
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if source not in self._graph:
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raise KeyError
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return self._graph[source].requires()
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def __getitem__(self, last):
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"""Return a partial dependency graph starting with the specified node.
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Return a subset of the dependency graph consisting of the specified
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node and 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 = map(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 leaves(self):
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"""Return an iterator over all of the leaf nodes in the graph."""
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return (requirer for requirer, required in self._graph.items()
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if not required)
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def roots(self):
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"""Return an iterator over all of the root nodes in the graph."""
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return (requirer for requirer, required in self.graph(
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reverse=True).items() if not required)
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def translate(self, transform):
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"""Translate all of the nodes using a transform function.
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Returns a new Dependencies object.
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"""
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def transform_key(key):
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return transform(key) if key is not None else None
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edges = self._graph.edges()
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return type(self)(tuple(map(transform_key, e)) for e in edges)
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def __str__(self):
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"""Return a human-readable string repr of the dependency graph."""
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return str(self._graph)
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def __repr__(self):
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"""Return a consistent string representation of the object."""
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edge_reprs = sorted(repr(e) for e in self._graph.edges())
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text = 'Dependencies([%s])' % ', '.join(edge_reprs)
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return text
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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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