working metrics plugin

with makeService tests, yet to write test for options

config.json

@@ -57,6 +57,7 @@
         "region": "IAD",
         "username": "stretchdev",
         "password": "REPLACE_WITH_REAL_PASSWORD",
-        "ttl": 432000
+        "ttl": 432000,
+        "interval": 60
     }
 }

otter/metrics.py

@@ -12,6 +12,8 @@
 
 from twisted.internet import task, defer
 from twisted.internet.endpoints import clientFromString
+from twisted.application.internet import TimerService
+from twisted.python import usage
 
 from silverberg.client import ConsistencyLevel
 from silverberg.cluster import RoundRobinCassandraCluster
@@ -290,8 +292,33 @@ def main(reactor, config, _print=False):
     yield client.disconnect()
 
 
+class Options(usage.Options):
+    """
+    Options for otter-metrics service
+    """
+
+    optParameters = [["config", "c", "config.json", "path to JSON configuration file"]]
+
+    def postOptions(self):
+        """
+        Parse config file and add nova service name
+        """
+        self.update(json.load(open(self['config'])))
+        self.update({'services': {'nova': 'cloudServersOpenStack'}})
+
+
+def makeService(config):
+    """
+    Set up the otter-metrics service.
+    """
+    from twisted.internet import reactor
+    config = dict(config)
+    return TimerService(
+        get_in(['metrics', 'interval'], config, default=60), main, reactor, config)
+
+
 if __name__ == '__main__':
-    config = json.load(open(sys.argv[1]))
+    config = json.load(open(sys.argv[2]))
     config['services'] = {'nova': 'cloudServersOpenStack'}
     # TODO: Take _print as cmd-line arg and pass it.
     task.react(main, (config, True))

otter/test/test_metrics.py

@@ -11,10 +11,11 @@
 
 from twisted.trial.unittest import SynchronousTestCase
 from twisted.internet.defer import succeed
+from twisted.application.internet import TimerService
 
 from otter.metrics import (
     get_scaling_groups, get_tenant_metrics, get_all_metrics, GroupMetrics,
-    add_to_cloud_metrics, main as metrics_main)
+    add_to_cloud_metrics, main as metrics_main, makeService)
 from otter.test.utils import patch, StubTreq2, matches
 from otter.util.http import headers
 from otter.log import BoundLog
@@ -250,3 +251,30 @@ def test_metrics_collected(self):
         self.add_to_cloud_metrics.assert_called_once_with(
             'm', 'id', 'r', 107, 26, 1)
         client.disconnect.assert_called_once_with()
+
+
+class ServiceTests(SynchronousTestCase):
+    """
+    Tests for :func:`otter.metrics.makeService` and :func:`otter.metrics.Options`
+    """
+
+    def test_make_service(self):
+        """
+        TimerService is returned with main as its function
+        """
+        c = {'metrics': {'interval': 20}}
+        s = makeService(c)
+        self.assertIsInstance(s, TimerService)
+        self.assertEqual(s.step, 20)
+        from twisted.internet.base import ReactorBase
+        self.assertEqual(
+            s.call,
+            (metrics_main, (matches(IsInstance(ReactorBase)), c), {}))
+
+    def test_make_service_no_interval(self):
+        """
+        makeService uses 60 as default interval if not provided in config
+        """
+        s = makeService({})
+        self.assertIsInstance(s, TimerService)
+        self.assertEqual(s.step, 60)