Add periodic task framework

This patch adds periodic timer to conductor service.
Any new periodic tasks need to be added to magnum/service/periodic.py
We add 2 default configure options to support periodic task:
    'periodic_enable', default=True
    'periodic_interval_max', default=60
These 2 options are for rpc_service.
PS:
We don't need to supervisor timers because timer itself won't have any
exception, and it is not a thread, which means can not be killed.

Partial-Implements: blueprint add-periodic-task
Co-Authored-By: ShaoHe Feng <shaohe.feng@intel.com>
Change-Id: I132d9cc89b26baf249b62b713ccd3776f0078d7d

etc/magnum/magnum.conf.sample

@@ -37,9 +37,12 @@
 # is displayed in the service's log file. (string value)
 #backdoor_port = <None>
 
-# Some periodic tasks can be run in a separate process. Should we run
-# them here? (boolean value)
-#run_external_periodic_tasks = true
+# Enable periodic tasks. (boolean value)
+#periodic_enable = true
+
+# Max interval size between periodic tasks execution in seconds.
+# (integer value)
+#periodic_interval_max = 60
 
 #
 # From oslo.log

magnum/common/rpc_service.py

@@ -21,6 +21,7 @@ from oslo_service import service
 
 from magnum.common import rpc
 from magnum.objects import base as objects_base
+from magnum.service import periodic
 
 
 # NOTE(paulczar):
@@ -39,6 +40,19 @@ TRANSPORT_ALIASES = {
     'magnum.openstack.common.rpc.impl_zmq': 'zmq',
 }
 
+periodic_opts = [
+    cfg.BoolOpt('periodic_enable',
+                default=True,
+                help='Enable periodic tasks.'),
+    cfg.IntOpt('periodic_interval_max',
+               default=60,
+               help='Max interval size between periodic tasks execution in '
+                    'seconds.'),
+]
+
+CONF = cfg.CONF
+CONF.register_opts(periodic_opts)
+
 
 class Service(service.Service):
     _server = None
@@ -55,6 +69,8 @@ class Service(service.Service):
                                                 serializer=serializer)
 
     def start(self):
+        if CONF.periodic_enable:
+            self.tg = periodic.setup(CONF)
         self._server.start()
 
     def wait(self):

magnum/opts.py

@@ -35,6 +35,7 @@ def list_opts():
                          magnum.common.magnum_keystoneclient.trust_opts,
                          magnum.common.paths.PATH_OPTS,
                          magnum.common.utils.UTILS_OPTS,
+                         magnum.common.rpc_service.periodic_opts
                          )),
         ('api', magnum.api.app.API_SERVICE_OPTS),
         ('bay', magnum.conductor.template_definition.template_def_opts),

magnum/service/periodic.py

@@ -0,0 +1,37 @@
+# Copyright (c) 2015 Intel 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.
+from oslo_log import log
+from oslo_service import periodic_task
+from oslo_service import threadgroup
+
+LOG = log.getLogger(__name__)
+
+
+class MagnumPeriodicTasks(periodic_task.PeriodicTasks):
+    '''Magnum periodic Task class
+
+    Any periodic task job need to be added into this class
+    '''
+    pass
+
+
+def setup(conf):
+    tg = threadgroup.ThreadGroup()
+    pt = MagnumPeriodicTasks(conf)
+    tg.add_dynamic_timer(
+        pt.run_periodic_tasks,
+        periodic_interval_max=conf.periodic_interval_max,
+        context=None)
+    return tg