279 lines
9.2 KiB
Python
279 lines
9.2 KiB
Python
# 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 logging
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import networkx as nx
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import os
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from stevedore import extension
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from diskimage_builder.block_device.exception import \
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BlockDeviceSetupException
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from diskimage_builder.block_device.plugin import NodeBase
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from diskimage_builder.block_device.plugin import PluginBase
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logger = logging.getLogger(__name__)
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_extensions = extension.ExtensionManager(
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namespace='diskimage_builder.block_device.plugin',
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invoke_on_load=False)
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# check if a given name is registered as a plugin
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def is_a_plugin(name):
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return any(
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_extensions.map(lambda x: x.name == name))
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def recurse_config(config, parent_base=None):
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"""Convert a config "tree" to it's canonical name/base graph version
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This is a recursive function to convert a YAML layout "tree"
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config into a "flat" graph-based config.
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Arguments:
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:param config: the incoming config dictionary
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:param parent_base: the name of the parent node, if any
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:return: a list of expanded, graph-based config items
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"""
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output = []
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this = {}
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# We should only have one key, with multiple values, being the
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# config entries. e.g. (this was checked by config_tree_to_graph)
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# # mkfs:
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# # type: ext4
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# # label: 1234
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assert len(config.items()) == 1
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for k, v in config.items():
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key = k
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values = v
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# If we don't have a base, we take the parent base; first element
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# can have no base, however.
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if 'base' not in values:
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if parent_base is not None:
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this['base'] = parent_base
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else:
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this['base'] = values['base']
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# If we don't have a name, it is made up as "key_base"
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if 'name' not in values:
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this['name'] = "%s_%s" % (key, this['base'])
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else:
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this['name'] = values['name']
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# Go through the values dictionary. Either this is a "plugin"
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# key that needs to be recursed, or it is a value that is part of
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# this config entry.
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for nk, nv in values.items():
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if nk == "partitions":
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# "partitions" is a special key of the "partitioning"
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# object. It is a list. Each list-entry gets treated
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# as a top-level entry, so we need to recurse it's
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# keys. But instead of becoming its own entry in the
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# graph, it gets attached to the .partitions attribute
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# of the parent. (see end for example)
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this['partitions'] = []
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for partition in nv:
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new_part = {}
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for pk, pv in partition.items():
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if is_a_plugin(pk):
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output.extend(
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recurse_config({pk: pv}, partition['name']))
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else:
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new_part[pk] = pv
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new_part['base'] = this['base']
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this['partitions'].append(new_part)
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elif is_a_plugin(nk):
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# is this key a plugin directive? If so, we recurse
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# into it.
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output.extend(recurse_config({nk: nv}, this['name']))
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else:
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# A value entry; just save as part of this entry
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this[nk] = nv
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output.append({k: this})
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return output
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def config_tree_to_graph(config):
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"""Turn a YAML config into a graph config
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Our YAML config is a list of entries. Each
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Arguments:
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:parm config: YAML config; either graph or tree
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:return: graph-based result
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"""
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output = []
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for entry in config:
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# Top-level entries should be a dictionary and have a plugin
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# registered for it
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if not isinstance(entry, dict):
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raise BlockDeviceSetupException(
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"Config entry not a dict: %s" % entry)
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keys = list(entry.keys())
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if len(keys) != 1:
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raise BlockDeviceSetupException(
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"Config entry top-level should be a single dict: %s" % entry)
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if not is_a_plugin(keys[0]):
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raise BlockDeviceSetupException(
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"Config entry is not a plugin value: %s" % entry)
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output.extend(recurse_config(entry))
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return output
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def create_graph(config, default_config, state):
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"""Generate configuration digraph
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Generate the configuration digraph from the config
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:param config: graph configuration file
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:param default_config: default parameters (from --params)
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:param state: reference to global state dictionary.
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Passed to :func:`PluginBase.__init__`
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:return: tuple with the graph object (a :class:`nx.Digraph`),
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ordered list of :class:`NodeBase` objects
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"""
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# This is the directed graph of nodes: each parse method must
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# add the appropriate nodes and edges.
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dg = nx.DiGraph()
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# check about dg.nodes, to support different networkx versions
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if hasattr(dg.nodes, '__iter__'):
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dg_nodes = dg.nodes
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else:
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dg_nodes = dg.node
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for config_entry in config:
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# this should have been checked by generate_config
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assert len(config_entry) == 1
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logger.debug("Config entry [%s]", config_entry)
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cfg_obj_name = list(config_entry.keys())[0]
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cfg_obj_val = config_entry[cfg_obj_name]
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# Instantiate a "plugin" object, passing it the
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# configuration entry
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# XXX : would a "factory" pattern for plugins, where we
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# make a method call on an object stevedore has instantiated
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# be better here?
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if not is_a_plugin(cfg_obj_name):
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raise BlockDeviceSetupException(
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("Config element [%s] is not implemented" % cfg_obj_name))
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plugin = _extensions[cfg_obj_name].plugin
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assert issubclass(plugin, PluginBase)
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cfg_obj = plugin(cfg_obj_val, default_config, state)
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# Ask the plugin for the nodes it would like to insert
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# into the graph. Some plugins, such as partitioning,
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# return multiple nodes from one config entry.
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nodes = cfg_obj.get_nodes()
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assert isinstance(nodes, list)
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for node in nodes:
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# plugins should return nodes...
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assert isinstance(node, NodeBase)
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# ensure node names are unique. networkx by default
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# just appends the attribute to the node dict for
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# existing nodes, which is not what we want.
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if node.name in dg_nodes:
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raise BlockDeviceSetupException(
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"Duplicate node name: %s" % (node.name))
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logger.debug("Adding %s : %s", node.name, node)
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dg.add_node(node.name, obj=node)
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# Now find edges
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for name, attr in dg.nodes(data=True):
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obj = attr['obj']
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# Unfortunately, we can not determine node edges just from
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# the configuration file. It's not always simply the
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# "base:" pointer. So ask nodes for a list of nodes they
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# want to point to. *mostly* it's just base: ... but
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# mounting is different.
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# edges_from are the nodes that point to us
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# edges_to are the nodes we point to
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edges_from, edges_to = obj.get_edges()
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logger.debug("Edges for %s: f:%s t:%s", name,
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edges_from, edges_to)
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for edge_from in edges_from:
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if edge_from not in dg_nodes:
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raise BlockDeviceSetupException(
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"Edge not defined: %s->%s" % (edge_from, name))
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dg.add_edge(edge_from, name)
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for edge_to in edges_to:
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if edge_to not in dg_nodes:
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raise BlockDeviceSetupException(
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"Edge not defined: %s->%s" % (name, edge_to))
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dg.add_edge(name, edge_to)
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# this can be quite helpful debugging but needs pydotplus which
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# isn't in requirements. for debugging, do
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# .tox/py27/bin/pip install pydotplus
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# DUMP_CONFIG_GRAPH=1 tox -e py27 -- specific_test
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# dotty /tmp/graph_dump.dot
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# to see helpful output
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if 'DUMP_CONFIG_GRAPH' in os.environ:
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nx.nx_pydot.write_dot(dg, '/tmp/graph_dump.dot')
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# Topological sort (i.e. create a linear array that satisfies
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# dependencies) and return the object list
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call_order_nodes = list(nx.topological_sort(dg))
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logger.debug("Call order: %s", call_order_nodes)
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call_order = [dg_nodes[n]['obj'] for n in call_order_nodes]
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return dg, call_order
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#
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# On partitioning: objects
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#
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# To be concrete --
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#
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# # partitioning:
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# # base: loop0
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# # name: mbr
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# # partitions:
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# # - name: partition1
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# # foo: bar
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# # mkfs:
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# # type: xfs
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# # mount:
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# # mount_point: /
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#
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# gets turned into the following graph:
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#
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# # partitioning:
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# # partitions:
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# # - name: partition1
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# # base: image0
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# # foo: bar
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#
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# # mkfs:
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# # base: partition1
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# # name: mkfs_partition1
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# # type: xfs
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#
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# # mount:
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# # base: mkfs_partition1
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# # name: mount_mkfs_partition1
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# # mount_point: /
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