text: # Copyright 2012 OpenStack Foundation
  #
  # 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 functools
  import inspect
  import time
  import types
  
  from oslo_log import log
  import six
  import stevedore
  
  from keystone.common import provider_api
  from keystone.i18n import _
  
  
  LOG = log.getLogger(__name__)
  
  if hasattr(inspect, 'getfullargspec'):
      getargspec = inspect.getfullargspec
  else:
      getargspec = inspect.getargspec
  
  
  def response_truncated(f):
      """Truncate the list returned by the wrapped function.
  
      This is designed to wrap Manager list_{entity} methods to ensure that
      any list limits that are defined are passed to the driver layer.  If a
      hints list is provided, the wrapper will insert the relevant limit into
      the hints so that the underlying driver call can try and honor it. If the
      driver does truncate the response, it will update the 'truncated' attribute
      in the 'limit' entry in the hints list, which enables the caller of this
      function to know if truncation has taken place.  If, however, the driver
      layer is unable to perform truncation, the 'limit' entry is simply left in
      the hints list for the caller to handle.
  
      A _get_list_limit() method is required to be present in the object class
      hierarchy, which returns the limit for this backend to which we will
      truncate.
  
      If a hints list is not provided in the arguments of the wrapped call then
      any limits set in the config file are ignored.  This allows internal use
      of such wrapped methods where the entire data set is needed as input for
      the calculations of some other API (e.g. get role assignments for a given
      project).
  
      """
      @functools.wraps(f)
      def wrapper(self, *args, **kwargs):
          if kwargs.get('hints') is None:
              return f(self, *args, **kwargs)
  
          list_limit = self.driver._get_list_limit()
          if list_limit:
              kwargs['hints'].set_limit(list_limit)
          return f(self, *args, **kwargs)
      return wrapper
  
  
  def load_driver(namespace, driver_name, *args):
      try:
          driver_manager = stevedore.DriverManager(namespace,
                                                   driver_name,
                                                   invoke_on_load=True,
                                                   invoke_args=args)
          return driver_manager.driver
      except stevedore.exception.NoMatches:
          msg = (_('Unable to find %(name)r driver in %(namespace)r.'))
          raise ImportError(msg % {'name': driver_name, 'namespace': namespace})
  
  
  class _TraceMeta(type):
      """A metaclass that, in trace mode, will log entry and exit of methods.
  
      This metaclass automatically wraps all methods on the class when
      instantiated with a decorator that will log entry/exit from a method
      when keystone is run in Trace log level.
      """
  
      @staticmethod
      def wrapper(__f, __classname):
          __argspec = getargspec(__f)
          __fn_info = '%(module)s.%(classname)s.%(funcname)s' % {
              'module': inspect.getmodule(__f).__name__,
              'classname': __classname,
              'funcname': __f.__name__
          }
          # NOTE(morganfainberg): Omit "cls" and "self" when printing trace logs
          # the index can be calculated at wrap time rather than at runtime.
          if __argspec.args and __argspec.args[0] in ('self', 'cls'):
              __arg_idx = 1
          else:
              __arg_idx = 0
  
          @functools.wraps(__f)
          def wrapped(*args, **kwargs):
              __exc = None
              __t = time.time()
              __do_trace = LOG.logger.getEffectiveLevel() <= log.TRACE
              __ret_val = None
              try:
                  if __do_trace:
                      LOG.trace('CALL => %s', __fn_info)
                  __ret_val = __f(*args, **kwargs)
              except Exception as e:  # nosec
                  __exc = e
                  raise
              finally:
                  if __do_trace:
                      __subst = {
                          'run_time': (time.time() - __t),
                          'passed_args': ', '.join([
                              ', '.join([repr(a)
                                         for a in args[__arg_idx:]]),
                              ', '.join(['%(k)s=%(v)r' % {'k': k, 'v': v}
                                         for k, v in kwargs.items()]),
                          ]),
                          'function': __fn_info,
                          'exception': __exc,
                          'ret_val': __ret_val,
                      }
                      if __exc is not None:
                          __msg = ('[%(run_time)ss] %(function)s '
                                   '(%(passed_args)s) => raised '
                                   '%(exception)r')
                      else:
                          # TODO(morganfainberg): find a way to indicate if this
                          # was a cache hit or cache miss.
                          __msg = ('[%(run_time)ss] %(function)s'
                                   '(%(passed_args)s) => %(ret_val)r')
                      LOG.trace(__msg, __subst)
              return __ret_val
          return wrapped
  
      def __new__(meta, classname, bases, class_dict):
          final_cls_dict = {}
          for attr_name, attr in class_dict.items():
              # NOTE(morganfainberg): only wrap public instances and methods.
              if (isinstance(attr, types.FunctionType) and
                      not attr_name.startswith('_')):
                  attr = _TraceMeta.wrapper(attr, classname)
              final_cls_dict[attr_name] = attr
          return type.__new__(meta, classname, bases, final_cls_dict)
  
  
  @six.add_metaclass(_TraceMeta)
  class Manager(object):
      """Base class for intermediary request layer.
  
      The Manager layer exists to support additional logic that applies to all
      or some of the methods exposed by a service that are not specific to the
      HTTP interface.
  
      It also provides a stable entry point to dynamic backends.
  
      An example of a probable use case is logging all the calls.
  
      """
  
      driver_namespace = None
      _provides_api = None
  
      def __init__(self, driver_name):
          if self._provides_api is None:
              raise ValueError('Programming Error: All managers must provide an '
                               'API that can be referenced by other components '
                               'of Keystone.')
          if driver_name is not None:
              self.driver = load_driver(self.driver_namespace, driver_name)
          self.__register_provider_api()
  
      def __register_provider_api(self):
          provider_api.ProviderAPIs._register_provider_api(
              name=self._provides_api, obj=self)
  
      def __getattr__(self, name):
          """Forward calls to the underlying driver.
  
          This method checks for a provider api before forwarding.
          """
          try:
              return getattr(provider_api.ProviderAPIs, name)
          except AttributeError:
              # NOTE(morgan): We didn't find a provider api, move on and
              # forward to the driver as expected.
              pass
  
          f = getattr(self.driver, name)
          if callable(f):
              # NOTE(dstanek): only if this is callable (class or function)
              # cache this
              setattr(self, name, f)
          return f
  