00da1982ce
This moves to a more generic config parser that doesn't have plugins parsing part of the tree. I understand why it ended up that way; we have "partitions" key which has special semantics compared to others keys and there was a desire to keep it isolated from core tree->graph code. But this isn't really isolated; you have to reverse-engineer several module-crossing boundaries, extras classes and repetitive recursive functions. Ultimately, plugins should have access to the node graph, but not participate in configuration parsing. This way we ensure that plugins can't invent new methods of configuration parsing. Note: unit tests produce the same tree -> graph conversion as the old method. i.e. this is not intended to have a functional change. Change-Id: I8a5d62a076a5a50597f2f1df3a8615afba6dadb2
174 lines
4.9 KiB
Python
174 lines
4.9 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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from stevedore import extension
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from diskimage_builder.block_device.exception import \
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BlockDeviceSetupException
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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 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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#
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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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