Add util method for getting rack config into scheduler from a config file

This adds a utility module to solver-scheduler's solver directory, together
with a method to get rack configurations from an external config file. This
will be needed by rack based constraints for solver scheduler.

Change-Id: I2f81fc47f374cb90d19dc1a1cafcb3beb76d4bb5

nova_solverscheduler/scheduler/solvers/utils.py

@@ -0,0 +1,87 @@
+# Copyright 2015 Cisco Systems, Inc.
+# 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.
+
+"""Utility methods for scheduler solvers."""
+
+import os.path
+
+from oslo_config import cfg
+from oslo_log import log as logging
+
+from nova.i18n import _LE
+
+rack_config_file_opts = [
+    cfg.StrOpt('rack_config',
+            default='',
+            help='The config file specifying physical rack configuration. By '
+                 'default Cisco\'s Neutron ML2 plugin config is supported, '
+                 'otherwise the format of the config file needs to be '
+                 'compatible with Cisco\'s Neutron ML2 plugin config file.'),
+    cfg.StrOpt('rack_config_prefix',
+            default='',
+            help='The section name in rack config file should start with the '
+                 'prefix, so the config parser can recognize the section as '
+                 'information of a specific rack or ToR switch. For example, '
+                 'in Cisco\'s Neutron ML2 plugin config a section name like '
+                 '[ml2_mech_cisco_nexus:1.1.1.1] identifies a specific ToR '
+                 'switch, then the prefix is \'ml2_mech_cisco_nexus\'.')
+]
+
+CONF = cfg.CONF
+CONF.register_opts(rack_config_file_opts)
+
+LOG = logging.getLogger(__name__)
+
+
+def get_host_racks_config():
+        """Read the rack config file to get physical rack configurations."""
+        # Example section in the file:
+        # [ml2_mech_cisco_nexus:1.1.1.1]
+        # compute1=1/1
+        # compute2=1/2
+        # ...
+
+        host_racks_map = {}
+        sections = {}
+
+        filepath = CONF.rack_config
+        if not filepath:
+            return host_racks_map
+
+        if not os.path.exists(filepath):
+            LOG.error(_LE("The rack config file is not found: %s"), filepath)
+            return host_racks_map
+
+        prefix = CONF.rack_config_prefix
+        if not prefix:
+            LOG.error(_LE("Rack config prefix is not set."))
+            return host_racks_map
+
+        try:
+            rack_config_parser = cfg.ConfigParser(filepath, sections)
+            rack_config_parser.parse()
+
+            for section_name in sections.keys():
+                if section_name.startswith(prefix):
+                    # section_name: rack id
+                    for key, value in sections[section_name].items():
+                        # key: host name, value: port id
+                        host_racks_map.setdefault(key, set([]))
+                        host_racks_map[key].add(section_name)
+        except Exception as e:
+            LOG.error(_LE("The rack config file is not parsed properly: %s"),
+                      str(e))
+
+        return host_racks_map

nova_solverscheduler/tests/scheduler/solvers/test_utils.py

@@ -0,0 +1,69 @@
+# Copyright 2015 Cisco Systems, Inc.
+# 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 os.path
+import tempfile
+
+from oslo_config import cfg
+
+from nova import test
+from nova_solverscheduler.scheduler.solvers import utils
+
+CONF = cfg.CONF
+
+
+class TestRackConfigLoader(test.NoDBTestCase):
+    """Test case for rack config file loading."""
+
+    _rack_config = '''
+[ml2_mech_cisco_nexus:1.1.1.1]
+compute1=1/1
+compute2=1/2
+[other-section]
+k=bla
+    '''
+
+    def setUp(self):
+        super(TestRackConfigLoader, self).setUp()
+        self.config = tempfile.NamedTemporaryFile(mode="w+t")
+        self.config.write(self._rack_config.lstrip())
+        self.config.seek(0)
+        self.config.flush()
+
+        self.config_path = None
+        if not os.path.isabs(self.config.name):
+            self.config_path = CONF.find_file(self.config.name)
+        elif os.path.exists(self.config.name):
+            self.config_path = self.config.name
+
+    def test_load_rack_config_happy_day(self):
+        self.flags(rack_config=self.config_path,
+                    rack_config_prefix='ml2_mech_cisco_nexus')
+        rackcfg = utils.get_host_racks_config()
+
+        ref_rackcfg = {
+            'compute1': set(['ml2_mech_cisco_nexus:1.1.1.1']),
+            'compute2': set(['ml2_mech_cisco_nexus:1.1.1.1'])
+        }
+        self.assertEqual(ref_rackcfg, rackcfg)
+
+    def test_load_rack_config_no_found(self):
+        self.flags(rack_config='non_existing_file')
+        rackcfg = utils.get_host_racks_config()
+        self.assertEqual({}, rackcfg)
+
+    def tearDown(self):
+        self.config.close()
+        super(TestRackConfigLoader, self).tearDown()