168 lines
6.9 KiB

# -*- coding: utf-8 -*-
# 2011 Steven Armstrong (steven-cdist at
# This file is part of cdist.
# cdist is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# cdist is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with cdist. If not, see <>.
import logging
import os
import itertools
import fnmatch
import cdist
log = logging.getLogger(__name__)
class CircularReferenceError(cdist.Error):
def __init__(self, cdist_object, required_object):
self.cdist_object = cdist_object
self.required_object = required_object
def __str__(self):
return 'Circular reference detected: %s -> %s' % (,
class RequirementNotFoundError(cdist.Error):
def __init__(self, requirement):
self.requirement = requirement
def __str__(self):
return 'Requirement could not be found: %s' % self.requirement
class DependencyResolver(object):
"""Cdist's dependency resolver.
>> resolver = DependencyResolver(list_of_objects)
# Easy access to the objects we are working with
>> resolver.objects['__some_type/object_id']
<CdistObject __some_type/object_id>
# Easy access to a specific objects dependencies
>> resolver.dependencies['__some_type/object_id']
[<CdistObject __other_type/dependency>, <CdistObject __some_type/object_id>]
# Pretty print the dependency graph
>> from pprint import pprint
>> pprint(resolver.dependencies)
# Iterate over all existing objects in the correct order
>> for cdist_object in resolver:
>> do_something_with(cdist_object)
def __init__(self, objects, logger=None):
self.objects = dict((, o) for o in objects)
self._dependencies = None
self.log = logger or log
def dependencies(self):
"""Build the dependency graph.
Returns a dict where the keys are the object names and the values are
lists of all dependencies including the key object itself.
if self._dependencies is None:
self._dependencies = d = {}
for name,cdist_object in self.objects.items():
resolved = []
unresolved = []
self._resolve_object_dependencies(cdist_object, resolved, unresolved)
d[name] = resolved
return self._dependencies
def find_requirements_by_name(self, requirements):
"""Takes a list of requirement patterns and returns a list of matching object instances.
Patterns are expected to be Unix shell-style wildcards for use with fnmatch.filter.
find_requirements_by_name(['__type/object_id', '__other_type/*']) ->
[<Object __type/object_id>, <Object __other_type/any>, <Object __other_type/match>]
object_names = self.objects.keys()
for pattern in requirements:
found = False
for requirement in fnmatch.filter(object_names, pattern):
found = True
yield self.objects[requirement]
if not found:
# FIXME: get rid of the singleton object_id, it should be invisible to the code -> hide it in Object
singleton = os.path.join(pattern, 'singleton')
if singleton in self.objects:
yield self.objects[singleton]
raise RequirementNotFoundError(pattern)
def _preprocess_requirements(self):
"""Find all autorequire dependencies and merge them to be just requirements
for further processing.
for cdist_object in self.objects.values():
if cdist_object.autorequire:
# The objects (children) that this cdist_object (parent) defined
# in it's type manifest shall inherit all explicit requirements
# that the parent has so that user defined requirements are
# fullfilled and processed in the expected order.
for auto_requirement in self.find_requirements_by_name(cdist_object.autorequire):
for requirement in cdist_object.requirements:
if requirement not in auto_requirement.requirements:
# On the other hand the parent shall depend on all the children
# it created so that the user can setup dependencies on it as a
# whole without having to know anything about the parents
# internals.
# As we changed the object on disc, we have to ensure it is not
# preprocessed again if someone would call us multiple times.
cdist_object.autorequire = []
def _resolve_object_dependencies(self, cdist_object, resolved, unresolved):
"""Resolve all dependencies for the given cdist_object and store them
in the list which is passed as the 'resolved' arguments.
resolved = []
unresolved = []
resolve_object_dependencies(some_object, resolved, unresolved)
print("Dependencies for %s: %s" % (some_object, resolved))
self.log.debug('Resolving dependencies for: %s' %
for required_object in self.find_requirements_by_name(cdist_object.requirements):
self.log.debug("Object %s requires %s", cdist_object, required_object)
if required_object not in resolved:
if required_object in unresolved:
raise CircularReferenceError(cdist_object, required_object)
self._resolve_object_dependencies(required_object, resolved, unresolved)
except RequirementNotFoundError as e:
raise cdist.CdistObjectError(cdist_object, "requires non-existing " + e.requirement)
def __iter__(self):
"""Iterate over all unique objects and yield them in the correct order.
iterable = itertools.chain(*self.dependencies.values())
# Keep record of objects that have already been seen
seen = set()
seen_add = seen.add
for cdist_object in itertools.filterfalse(seen.__contains__, iterable):
yield cdist_object