text: # 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.
  
  from cinder.openstack.common.gettextutils import _  # noqa
  from cinder.openstack.common import log as logging
  from cinder.openstack.common.scheduler import filters
  
  LOG = logging.getLogger(__name__)
  
  
  class IgnoreAttemptedHostsFilter(filters.BaseHostFilter):
      """Filter out previously attempted hosts
  
      A host passes this filter if it has not already been attempted for
      scheduling. The scheduler needs to add previously attempted hosts
      to the 'retry' key of filter_properties in order for this to work
      correctly.  For example:
      {
          'retry': {
                  'hosts': ['host1', 'host2'],
                  'num_attempts': 3,
              }
      }
      """
  
      def host_passes(self, host_state, filter_properties):
          """Skip nodes that have already been attempted."""
          attempted = filter_properties.get('retry', None)
          if not attempted:
              # Re-scheduling is disabled
              LOG.debug(_("Re-scheduling is disabled."))
              return True
  
          hosts = attempted.get('hosts', [])
          host = host_state.host
  
          passes = host not in hosts
          pass_msg = "passes" if passes else "fails"
  
          LOG.debug(_("Host %(host)s %(pass_msg)s.  Previously tried hosts: "
                      "%(hosts)s") % {'host': host,
                                      'pass_msg': pass_msg,
                                      'hosts': hosts})
          return passes
  