text: # Copyright 2011 OpenStack Foundation.
  # Copyright 2012, Red Hat, Inc.
  #
  #    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.
  
  """
  Exception related utilities.
  """
  
  import logging
  import sys
  import time
  import traceback
  
  import six
  
  from volt.openstack.common.gettextutils import _LE
  
  
  class save_and_reraise_exception(object):
      """Save current exception, run some code and then re-raise.
  
      In some cases the exception context can be cleared, resulting in None
      being attempted to be re-raised after an exception handler is run. This
      can happen when eventlet switches greenthreads or when running an
      exception handler, code raises and catches an exception. In both
      cases the exception context will be cleared.
  
      To work around this, we save the exception state, run handler code, and
      then re-raise the original exception. If another exception occurs, the
      saved exception is logged and the new exception is re-raised.
  
      In some cases the caller may not want to re-raise the exception, and
      for those circumstances this context provides a reraise flag that
      can be used to suppress the exception.  For example::
  
        except Exception:
            with save_and_reraise_exception() as ctxt:
                decide_if_need_reraise()
                if not should_be_reraised:
                    ctxt.reraise = False
  
      If another exception occurs and reraise flag is False,
      the saved exception will not be logged.
  
      If the caller wants to raise new exception during exception handling
      he/she sets reraise to False initially with an ability to set it back to
      True if needed::
  
        except Exception:
            with save_and_reraise_exception(reraise=False) as ctxt:
                [if statements to determine whether to raise a new exception]
                # Not raising a new exception, so reraise
                ctxt.reraise = True
      """
      def __init__(self, reraise=True):
          self.reraise = reraise
  
      def __enter__(self):
          self.type_, self.value, self.tb, = sys.exc_info()
          return self
  
      def __exit__(self, exc_type, exc_val, exc_tb):
          if exc_type is not None:
              if self.reraise:
                  logging.error(_LE('Original exception being dropped: %s'),
                                traceback.format_exception(self.type_,
                                                           self.value,
                                                           self.tb))
              return False
          if self.reraise:
              six.reraise(self.type_, self.value, self.tb)
  
  
  def forever_retry_uncaught_exceptions(infunc):
      def inner_func(*args, **kwargs):
          last_log_time = 0
          last_exc_message = None
          exc_count = 0
          while True:
              try:
                  return infunc(*args, **kwargs)
              except Exception as exc:
                  this_exc_message = six.u(str(exc))
                  if this_exc_message == last_exc_message:
                      exc_count += 1
                  else:
                      exc_count = 1
                  # Do not log any more frequently than once a minute unless
                  # the exception message changes
                  cur_time = int(time.time())
                  if (cur_time - last_log_time > 60 or
                          this_exc_message != last_exc_message):
                      logging.exception(
                          _LE('Unexpected exception occurred %d time(s)... '
                              'retrying.') % exc_count)
                      last_log_time = cur_time
                      last_exc_message = this_exc_message
                      exc_count = 0
                  # This should be a very rare event. In case it isn't, do
                  # a sleep.
                  time.sleep(1)
      return inner_func
  