Rework application prefix configuration.

Use a default of `None` instead of `applications` if the neither service
nor environment keys are set.

sprockets_statsd/mixins.py

@@ -11,25 +11,12 @@ class Application(web.Application):
     """Mix this into your application to add a statsd connection.
 
     This mix-in is configured by the ``statsd`` settings key.  The
-    value should be a dictionary with the following keys.
+    value is a dictionary with the following keys.
 
     +-------------------+---------------------------------------------+
     | host              | the statsd host to send metrics to          |
     +-------------------+---------------------------------------------+
-    | port              | TCP port number that statsd is listening on |
+    | port              | port number that statsd is listening on     |
-    +-------------------+---------------------------------------------+
-
-    *host* defaults to the :envvar:`STATSD_HOST` environment variable.
-    If this value is not set, then the statsd connector **WILL NOT**
-    be enabled.
-
-    *port* defaults to the :envvar:`STATSD_PORT` environment variable
-    with a back up default of 8125 if the environment variable is not
-    set.
-
-    The following keys MAY also be specified to fine tune the statsd
-    connection.
-
     +-------------------+---------------------------------------------+
     | prefix            | segment to prefix to metrics.               |
     +-------------------+---------------------------------------------+
@@ -41,14 +28,27 @@ class Application(web.Application):
     |                   | connection                                  |
     +-------------------+---------------------------------------------+
 
-    *prefix* defaults to ``applications.<service>.<environment>`` where
+    **host** defaults to the :envvar:`STATSD_HOST` environment variable.
-    *<service>* and *<environment>* are replaced with the keys from
+    If this value is not set, then the statsd connector *WILL NOT* be
-    `settings` if they are present.
+    enabled.
 
-    *reconnect_timeout* defaults to 1.0 seconds which limits the
+    **port** defaults to the :envvar:`STATSD_PORT` environment variable
+    with a back up default of 8125 if the environment variable is not
+    set.
+
+    **prefix** is prefixed to all metric paths.  This provides a
+    namespace for metrics so that each applications metrics are maintained
+    in separate buckets.
+
+    If the *service* and *environment* keys are set in ``settings``,
+    then the default prefix is ``applications.<service>.<environment>``.
+    This is a convenient way to maintain consistent metric paths when
+    you are managing a larger number of services.
+
+    **reconnect_timeout** defaults to 1.0 seconds which limits the
     aggressiveness of creating new TCP connections.
 
-    *wait_timeout* defaults to 0.1 seconds which ensures that the
+    **wait_timeout** defaults to 0.1 seconds which ensures that the
     processor quickly responds to connection faults.
 
     """
@@ -58,12 +58,15 @@ class Application(web.Application):
         statsd_settings.setdefault('port',
                                    os.environ.get('STATSD_PORT', '8125'))
 
-        prefix = ['applications']
+        try:
-        if 'service' in settings:
+            prefix = '.'.join([
-            prefix.append(settings['service'])
+                'applications',
-        if 'environment' in settings:
+                settings['service'],
-            prefix.append(settings['environment'])
+                settings['environment'],
-        statsd_settings.setdefault('prefix', '.'.join(prefix))
+            ])
+        except KeyError:
+            prefix = None
+        statsd_settings.setdefault('prefix', prefix)
 
         super().__init__(*args, **settings)
 

tests/test_mixins.py

@@ -45,7 +45,7 @@ class ApplicationTests(testing.AsyncTestCase):
         self.assertIsNone(app.settings['statsd']['host'],
                           'default host value should be None')
         self.assertEqual(8125, app.settings['statsd']['port'])
-        self.assertEqual('applications', app.settings['statsd']['prefix'])
+        self.assertEqual(None, app.settings['statsd']['prefix'])
 
     def test_that_statsd_settings_read_from_environment(self):
         self.setenv('STATSD_HOST', 'statsd')
@@ -56,22 +56,21 @@ class ApplicationTests(testing.AsyncTestCase):
         self.assertEqual('statsd', app.settings['statsd']['host'])
         self.assertEqual(5218, app.settings['statsd']['port'])
 
-    def test_that_service_included_in_prefix_if_set(self):
+    def test_prefix_when_only_service_is_set(self):
         app = sprockets_statsd.mixins.Application(service='blah')
         self.assertIn('statsd', app.settings)
-        self.assertEqual('applications.blah', app.settings['statsd']['prefix'])
+        self.assertEqual(None, app.settings['statsd']['prefix'])
 
-    def test_that_environment_included_in_prefix_if_set(self):
+    def test_prefix_when_only_environment_is_set(self):
         app = sprockets_statsd.mixins.Application(environment='whatever')
         self.assertIn('statsd', app.settings)
-        self.assertEqual('applications.whatever',
+        self.assertEqual(None, app.settings['statsd']['prefix'])
-                         app.settings['statsd']['prefix'])
 
-    def test_fully_specified_prefix(self):
+    def test_prefix_default_when_service_and_environment_are_set(self):
-        app = sprockets_statsd.mixins.Application(environment='whatever',
+        app = sprockets_statsd.mixins.Application(environment='development',
-                                                  service='blah')
+                                                  service='my-service')
         self.assertIn('statsd', app.settings)
-        self.assertEqual('applications.blah.whatever',
+        self.assertEqual('applications.my-service.development',
                          app.settings['statsd']['prefix'])
 
     def test_overridden_settings(self):
@@ -138,8 +137,11 @@ class RequestHandlerTests(testing.AsyncHTTPTestCase):
         self.io_loop.spawn_callback(self.statsd_server.run)
         self.io_loop.run_sync(self.statsd_server.wait_running)
 
-        self.app.settings['statsd']['host'] = self.statsd_server.host
+        self.app.settings['statsd'].update({
-        self.app.settings['statsd']['port'] = self.statsd_server.port
+            'host': self.statsd_server.host,
+            'port': self.statsd_server.port,
+            'prefix': 'applications.service',
+        })
         self.io_loop.run_sync(self.app.start_statsd)
 
     def tearDown(self):
@@ -183,7 +185,7 @@ class RequestHandlerTests(testing.AsyncHTTPTestCase):
         self.wait_for_metrics()
 
         path, _, type_code = self.find_metric('Handler.GET.200')
-        self.assertEqual(path, 'applications.timers.Handler.GET.200')
+        self.assertEqual(path, 'applications.service.timers.Handler.GET.200')
         self.assertEqual('ms', type_code)
 
     def test_execution_timer(self):
@@ -192,7 +194,7 @@ class RequestHandlerTests(testing.AsyncHTTPTestCase):
         self.wait_for_metrics()
 
         path, _, type_code = self.find_metric('execution-timer')
-        self.assertEqual('applications.timers.execution-timer', path)
+        self.assertEqual('applications.service.timers.execution-timer', path)
         self.assertEqual('ms', type_code)
 
     def test_counter(self):
@@ -201,7 +203,7 @@ class RequestHandlerTests(testing.AsyncHTTPTestCase):
         self.wait_for_metrics()
 
         path, value, type_code = self.find_metric('request-count')
-        self.assertEqual('applications.counters.request-count', path)
+        self.assertEqual('applications.service.counters.request-count', path)
         self.assertEqual(1.0, value)
         self.assertEqual('c', type_code)