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OpenStack Study: json_filter.py**** CubicPower OpenStack Study ****
# Copyright (c) 2011 OpenStack Foundation # All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. import operator import six from nova.openstack.common import jsonutils from nova.scheduler import filters
**** CubicPower OpenStack Study **** class JsonFilter(filters.BaseHostFilter): """Host Filter to allow simple JSON-based grammar for selecting hosts. """
**** CubicPower OpenStack Study **** def _op_compare(self, args, op): """Returns True if the specified operator can successfully compare the first item in the args with all the rest. Will return False if only one item is in the list. """ if len(args) < 2: return False if op is operator.contains: bad = args[0] not in args[1:] else: bad = [arg for arg in args[1:] if not op(args[0], arg)] return not bool(bad)
**** CubicPower OpenStack Study **** def _equals(self, args): """First term is == all the other terms.""" return self._op_compare(args, operator.eq)
**** CubicPower OpenStack Study **** def _less_than(self, args): """First term is < all the other terms.""" return self._op_compare(args, operator.lt)
**** CubicPower OpenStack Study **** def _greater_than(self, args): """First term is > all the other terms.""" return self._op_compare(args, operator.gt)
**** CubicPower OpenStack Study **** def _in(self, args): """First term is in set of remaining terms.""" return self._op_compare(args, operator.contains)
**** CubicPower OpenStack Study **** def _less_than_equal(self, args): """First term is <= all the other terms.""" return self._op_compare(args, operator.le)
**** CubicPower OpenStack Study **** def _greater_than_equal(self, args): """First term is >= all the other terms.""" return self._op_compare(args, operator.ge)
**** CubicPower OpenStack Study **** def _not(self, args): """Flip each of the arguments.""" return [not arg for arg in args]
**** CubicPower OpenStack Study **** def _or(self, args): """True if any arg is True.""" return any(args)
**** CubicPower OpenStack Study **** def _and(self, args): """True if all args are True.""" return all(args) commands = { '=': _equals, '<': _less_than, '>': _greater_than, 'in': _in, '<=': _less_than_equal, '>=': _greater_than_equal, 'not': _not, 'or': _or, 'and': _and, }
**** CubicPower OpenStack Study **** def _parse_string(self, string, host_state): """Strings prefixed with $ are capability lookups in the form '$variable' where 'variable' is an attribute in the HostState class. If $variable is a dictionary, you may use: $variable.dictkey """ if not string: return None if not string.startswith("$"): return string path = string[1:].split(".") obj = getattr(host_state, path[0], None) if obj is None: return None for item in path[1:]: obj = obj.get(item, None) if obj is None: return None return obj
**** CubicPower OpenStack Study **** def _process_filter(self, query, host_state): """Recursively parse the query structure.""" if not query: return True cmd = query[0] method = self.commands[cmd] cooked_args = [] for arg in query[1:]: if isinstance(arg, list): arg = self._process_filter(arg, host_state) elif isinstance(arg, six.string_types): arg = self._parse_string(arg, host_state) if arg is not None: cooked_args.append(arg) result = method(self, cooked_args) return result
**** CubicPower OpenStack Study **** def host_passes(self, host_state, filter_properties): """Return a list of hosts that can fulfill the requirements specified in the query. """ try: query = filter_properties['scheduler_hints']['query'] except KeyError: query = None if not query: return True # NOTE(comstud): Not checking capabilities or service for # enabled/disabled so that a provided json filter can decide result = self._process_filter(jsonutils.loads(query), host_state) if isinstance(result, list): # If any succeeded, include the host result = any(result) if result: # Filter it out. return True return False
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