Alarm: Use stevedore to load the service class

A deployer must choice a driver with a name not a python class

This change does that but also keep backward compatibility.

DocImpact
Closes-Bug: #1362006

Change-Id: I41183b1a0c0f07c15efd6e0704a7a281b8ec7284

ceilometer/cmd/alarm.py

@@ -15,21 +15,23 @@
 # under the License.
 
 from oslo.config import cfg
-from oslo.utils import importutils
+from stevedore import driver
 
 from ceilometer.alarm import service as alarm_service
+from ceilometer.openstack.common import log
 from ceilometer.openstack.common import service as os_service
 from ceilometer import service
 
 
 OPTS = [
-    cfg.StrOpt('evaluation_service',
-               default='ceilometer.alarm.service.SingletonAlarmService',
-               help='Class to launch as alarm evaluation service.'),
+    cfg.StrOpt('evaluation_service', default='singleton',
+               help='Driver to use for alarm evaluation service.'),
 ]
 
 cfg.CONF.register_opts(OPTS, group='alarm')
 
+LOG = log.getLogger(__name__)
+
 
 def notifier():
     service.prepare_service()
@@ -38,5 +40,10 @@ def notifier():
 
 def evaluator():
     service.prepare_service()
-    eval_service = importutils.import_object(cfg.CONF.alarm.evaluation_service)
-    os_service.launch(eval_service).wait()
+    eval_service_mgr = driver.DriverManager(
+        "ceilometer.alarm.evaluator_service",
+        cfg.CONF.alarm.evaluation_service,
+        invoke_on_load=True)
+    LOG.debug("Alarm evaluator loaded: %s" %
+              eval_service_mgr.driver.__class__.__name__)
+    os_service.launch(eval_service_mgr.driver).wait()

ceilometer/tests/test_bin.py

@@ -100,6 +100,46 @@ class BinSendSampleTestCase(base.BaseTestCase):
         self.assertEqual(0, subp.wait())
 
 
+class BinAlarmEvaluatorServiceTestCase(base.BaseTestCase):
+    def _do_test(self, driver, driver_class):
+        pipeline_cfg_file = self.path_get('etc/ceilometer/pipeline.yaml')
+        content = ("[DEFAULT]\n"
+                   "rpc_backend=fake\n"
+                   "pipeline_cfg_file={0}\n"
+                   "debug=true\n"
+                   "[database]\n"
+                   "time_to_live=1\n"
+                   "connection=log://localhost\n".format(pipeline_cfg_file))
+
+        if driver:
+            content += "[alarm]\nevaluation_service=%s\n" % driver
+
+        self.tempfile = fileutils.write_to_tempfile(content=content,
+                                                    prefix='ceilometer',
+                                                    suffix='.conf')
+        self.subp = subprocess.Popen(['ceilometer-alarm-evaluator',
+                                      "--config-file=%s" % self.tempfile],
+                                     stderr=subprocess.PIPE)
+        err = self.subp.stderr.read(1024)
+        self.assertIn("Alarm evaluator loaded: %s" % driver_class, err)
+
+    def tearDown(self):
+        super(BinAlarmEvaluatorServiceTestCase, self).tearDown()
+        self.subp.kill()
+        self.subp.wait()
+        os.remove(self.tempfile)
+
+    def test_default_config(self):
+        self._do_test(None, "SingletonAlarmService")
+
+    def test_backward_compat(self):
+        self._do_test("ceilometer.alarm.service.PartitionedAlarmService",
+                      "PartitionedAlarmService")
+
+    def test_partitioned_driver(self):
+        self._do_test("partitioned", "PartitionedAlarmService")
+
+
 class BinApiTestCase(base.BaseTestCase):
 
     def setUp(self):

doc/source/configuration.rst

@@ -192,6 +192,20 @@ drop_unmatched_notifications        False                                   If s
 definitions_cfg_file                event_definitions.yaml                  Name of event definitions config file (yaml format)
 ==================================  ======================================  ==============================================================
 
+Alarming
+========
+
+The following options in the [alarm] configuration section affect the configuration of alarm services
+
+======================  ==============  ====================================================================================
+Parameter               Default         Note
+======================  ==============  ====================================================================================
+evaluation_service      singleton       Driver to use for alarm evaluation service:
+                                          * singleton:   All alarms are evaluated by one alarm evaluation service instance
+                                          * partitioned: All alarms are dispatched across all alarm evaluation service
+                                            instances to be evaluate
+======================  ==============  ====================================================================================
+
 
 
 General options

setup.cfg

@@ -222,6 +222,13 @@ ceilometer.alarm.evaluator =
     threshold = ceilometer.alarm.evaluator.threshold:ThresholdEvaluator
     combination = ceilometer.alarm.evaluator.combination:CombinationEvaluator
 
+ceilometer.alarm.evaluator_service =
+    singleton = ceilometer.alarm.service:SingletonAlarmService
+    partitioned = ceilometer.alarm.service:PartitionedAlarmService
+    # NOTE(sileht): for backward compatibility
+    ceilometer.alarm.service.SingletonAlarmService = ceilometer.alarm.service:SingletonAlarmService
+    ceilometer.alarm.service.PartitionedAlarmService = ceilometer.alarm.service:PartitionedAlarmService
+
 ceilometer.alarm.notifier =
     log = ceilometer.alarm.notifier.log:LogAlarmNotifier
     test = ceilometer.alarm.notifier.test:TestAlarmNotifier