Simple service for singleton threshold eval

A skeleton service for singleton threshold evaluation
of alarms (i.e. with trivial global partitioning).

Change-Id: I6081ac92b04ecffa1fb8783c36e9fe12004c2129

ceilometer/alarm/service.py

@@ -0,0 +1,90 @@
+# -*- encoding: utf-8 -*-
+#
+# Copyright © 2013 Red Hat, Inc
+#
+# Author: Eoghan Glynn <eglynn@redhat.com>
+#
+# 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.config import cfg
+from stevedore import extension
+
+from ceilometer.service import prepare_service
+from ceilometer.openstack.common import log
+from ceilometer.openstack.common import service as os_service
+from ceilometerclient import client as ceiloclient
+
+OPTS = [
+    cfg.IntOpt('threshold_evaluation_interval',
+               default=60,
+               help='Period of threshold evaluation cycle, should'
+                    ' be >= than configured pipeline interval for'
+                    ' collection of underlying metrics.'),
+]
+
+cfg.CONF.register_opts(OPTS, group='alarm')
+
+LOG = log.getLogger(__name__)
+
+
+class SingletonAlarmService(os_service.Service):
+
+    ALARM_NAMESPACE = 'ceilometer.alarm'
+
+    def __init__(self):
+        super(SingletonAlarmService, self).__init__()
+        self.extension_manager = extension.ExtensionManager(
+            namespace=self.ALARM_NAMESPACE,
+            invoke_on_load=True,
+        )
+
+    def start(self):
+        super(SingletonAlarmService, self).start()
+        for ext in self.extension_manager.extensions:
+            if ext.name == 'threshold_eval':
+                self.threshold_eval = ext.obj
+                interval = cfg.CONF.alarm.threshold_evaluation_interval
+                args = [ext.obj, self._client()]
+                self.tg.add_timer(
+                    interval,
+                    self._evaluate_all_alarms,
+                    0,
+                    *args)
+                break
+        # Add a dummy thread to have wait() working
+        self.tg.add_timer(604800, lambda: None)
+
+    @staticmethod
+    def _client():
+        auth_config = cfg.CONF.service_credentials
+        creds = dict(
+            os_auth_url=auth_config.os_auth_url,
+            os_tenant_name=auth_config.os_tenant_name,
+            os_password=auth_config.os_password,
+            os_username=auth_config.os_username
+        )
+        return ceiloclient.get_client(2, **creds)
+
+    @staticmethod
+    def _evaluate_all_alarms(threshold_eval, api_client):
+        try:
+            alarms = api_client.alarms.list()
+            threshold_eval.assign_alarms(alarms)
+            threshold_eval.evaluate()
+        except Exception:
+            LOG.exception(_('threshold evaluation cycle failed'))
+
+
+def singleton_alarm():
+    prepare_service()
+    os_service.launch(SingletonAlarmService()).wait()