7d61b77708
- inherit explicit requirements that the user defined himself - but _not_ implicit requirements that cdist added for autorequire Changes: - added new .autorequire property to CdistObject to keep track of implicit autorequire dependencies - Emulator appends implicit requirements to this .autorequire property - DependencyResolver preprocess these .autorequire properties before resolving normal dependencies - refactored and documented DependencyResolver so it's clearer what happens and easier to use from tests - update test cases to match new DependencyResolver behaviour Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
167 lines
6.9 KiB
Python
167 lines
6.9 KiB
Python
# -*- coding: utf-8 -*-
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#
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# 2011 Steven Armstrong (steven-cdist at armstrong.cc)
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#
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# This file is part of cdist.
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#
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# cdist is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# cdist is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with cdist. If not, see <http://www.gnu.org/licenses/>.
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#
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#
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import logging
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import os
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import itertools
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import fnmatch
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import cdist
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log = logging.getLogger(__name__)
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class CircularReferenceError(cdist.Error):
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def __init__(self, cdist_object, required_object):
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self.cdist_object = cdist_object
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self.required_object = required_object
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def __str__(self):
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return 'Circular reference detected: %s -> %s' % (self.cdist_object.name, self.required_object.name)
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class RequirementNotFoundError(cdist.Error):
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def __init__(self, requirement):
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self.requirement = requirement
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def __str__(self):
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return 'Requirement could not be found: %s' % self.requirement
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class DependencyResolver(object):
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"""Cdist's dependency resolver.
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Usage:
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>> resolver = DependencyResolver(list_of_objects)
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# Easy access to the objects we are working with
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>> resolver.objects['__some_type/object_id']
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<CdistObject __some_type/object_id>
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# Easy access to a specific objects dependencies
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>> resolver.dependencies['__some_type/object_id']
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[<CdistObject __other_type/dependency>, <CdistObject __some_type/object_id>]
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# Pretty print the dependency graph
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>> from pprint import pprint
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>> pprint(resolver.dependencies)
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# Iterate over all existing objects in the correct order
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>> for cdist_object in resolver:
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>> do_something_with(cdist_object)
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"""
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def __init__(self, objects, logger=None):
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self.objects = dict((o.name, o) for o in objects)
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self._dependencies = None
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self.log = logger or log
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@property
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def dependencies(self):
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"""Build the dependency graph.
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Returns a dict where the keys are the object names and the values are
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lists of all dependencies including the key object itself.
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"""
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if self._dependencies is None:
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self._dependencies = d = {}
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self._preprocess_requirements()
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for name,cdist_object in self.objects.items():
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resolved = []
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unresolved = []
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self._resolve_object_dependencies(cdist_object, resolved, unresolved)
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d[name] = resolved
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return self._dependencies
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def find_requirements_by_name(self, requirements):
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"""Takes a list of requirement patterns and returns a list of matching object instances.
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Patterns are expected to be Unix shell-style wildcards for use with fnmatch.filter.
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find_requirements_by_name(['__type/object_id', '__other_type/*']) ->
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[<Object __type/object_id>, <Object __other_type/any>, <Object __other_type/match>]
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"""
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object_names = self.objects.keys()
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for pattern in requirements:
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found = False
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for requirement in fnmatch.filter(object_names, pattern):
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found = True
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yield self.objects[requirement]
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if not found:
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# FIXME: get rid of the singleton object_id, it should be invisible to the code -> hide it in Object
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singleton = os.path.join(pattern, 'singleton')
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if singleton in self.objects:
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yield self.objects[singleton]
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else:
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raise RequirementNotFoundError(pattern)
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def _preprocess_requirements(self):
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"""Find all autorequire dependencies and merge them to be just requirements
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for further processing.
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"""
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for cdist_object in self.objects.values():
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if cdist_object.autorequire:
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# The objects (children) that this cdist_object (parent) defined
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# in it's type manifest shall inherit all explicit requirements
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# that the parent has so that user defined requirements are
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# fullfilled and processed in the expected order.
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for auto_requirement in self.find_requirements_by_name(cdist_object.autorequire):
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for requirement in cdist_object.requirements:
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if requirement not in auto_requirement.requirements:
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auto_requirement.requirements.append(requirement)
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# On the other hand the parent shall depend on all the children
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# it created so that the user can setup dependencies on it as a
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# whole without having to know anything about the parents
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# internals.
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cdist_object.requirements.extend(cdist_object.autorequire)
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# As we changed the object on disc, we have to ensure it is not
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# preprocessed again if someone would call us multiple times.
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cdist_object.autorequire = []
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def _resolve_object_dependencies(self, cdist_object, resolved, unresolved):
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"""Resolve all dependencies for the given cdist_object and store them
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in the list which is passed as the 'resolved' arguments.
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e.g.
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resolved = []
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unresolved = []
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resolve_object_dependencies(some_object, resolved, unresolved)
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print("Dependencies for %s: %s" % (some_object, resolved))
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"""
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self.log.debug('Resolving dependencies for: %s' % cdist_object.name)
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try:
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unresolved.append(cdist_object)
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for required_object in self.find_requirements_by_name(cdist_object.requirements):
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self.log.debug("Object %s requires %s", cdist_object, required_object)
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if required_object not in resolved:
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if required_object in unresolved:
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raise CircularReferenceError(cdist_object, required_object)
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self._resolve_object_dependencies(required_object, resolved, unresolved)
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resolved.append(cdist_object)
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unresolved.remove(cdist_object)
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except RequirementNotFoundError as e:
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raise cdist.CdistObjectError(cdist_object, "requires non-existing " + e.requirement)
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def __iter__(self):
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"""Iterate over all unique objects and yield them in the correct order.
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"""
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iterable = itertools.chain(*self.dependencies.values())
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# Keep record of objects that have already been seen
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seen = set()
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seen_add = seen.add
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for cdist_object in itertools.filterfalse(seen.__contains__, iterable):
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seen_add(cdist_object)
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yield cdist_object
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