Add $STATSD_PREFIX support.

docs/index.rst

@@ -17,6 +17,11 @@ the following environment variables.
 
    The TCP port number that the StatsD server is listening on.  This defaults to 8125 if it is not configured.
 
+.. envvar:: STATSD_PREFIX
+
+   Optional prefix to use for metric paths.  See the documentation for :class:`~sprockets_statsd.mixins.Application`
+   for addition notes on setting the path prefix.
+
 .. envvar:: STATSD_PROTOCOL
 
    The IP protocol to use when connecting to the StatsD server.  You can specify either "tcp" or "udp".  The

sprockets_statsd/mixins.py

@@ -73,15 +73,18 @@ class Application(web.Application):
         statsd_settings.setdefault('protocol',
                                    os.environ.get('STATSD_PROTOCOL', 'tcp'))
 
-        try:
-            prefix = '.'.join([
-                'applications',
-                settings['service'],
-                settings['environment'],
-            ])
-        except KeyError:
-            prefix = None
-        statsd_settings.setdefault('prefix', prefix)
+        if os.environ.get('STATSD_PREFIX'):
+            statsd_settings.setdefault('prefix', os.environ['STATSD_PREFIX'])
+        else:
+            try:
+                prefix = '.'.join([
+                    'applications',
+                    settings['service'],
+                    settings['environment'],
+                ])
+            except KeyError:
+                prefix = None
+            statsd_settings.setdefault('prefix', prefix)
 
         super().__init__(*args, **settings)
 

tests/test_mixins.py

@@ -51,6 +51,7 @@ class ApplicationTests(AsyncTestCaseWithTimeout):
     def test_statsd_setting_defaults(self):
         self.unsetenv('STATSD_HOST')
         self.unsetenv('STATSD_PORT')
+        self.unsetenv('STATSD_PREFIX')
         self.unsetenv('STATSD_PROTOCOL')
 
         app = sprockets_statsd.mixins.Application()
@@ -64,12 +65,14 @@ class ApplicationTests(AsyncTestCaseWithTimeout):
     def test_that_statsd_settings_read_from_environment(self):
         self.setenv('STATSD_HOST', 'statsd')
         self.setenv('STATSD_PORT', '5218')
+        self.setenv('STATSD_PREFIX', 'my-service')
         self.setenv('STATSD_PROTOCOL', 'udp')
 
         app = sprockets_statsd.mixins.Application()
         self.assertIn('statsd', app.settings)
         self.assertEqual('statsd', app.settings['statsd']['host'])
         self.assertEqual(5218, app.settings['statsd']['port'])
+        self.assertEqual('my-service', app.settings['statsd']['prefix'])
         self.assertEqual('udp', app.settings['statsd']['protocol'])
 
     def test_prefix_when_only_service_is_set(self):
@@ -92,6 +95,7 @@ class ApplicationTests(AsyncTestCaseWithTimeout):
     def test_overridden_settings(self):
         self.setenv('STATSD_HOST', 'statsd')
         self.setenv('STATSD_PORT', '9999')
+        self.setenv('STATSD_PREFIX', 'service')
         self.setenv('STATSD_PROTOCOL', 'tcp')
         app = sprockets_statsd.mixins.Application(
             statsd={