Stop mix-in from failing when not installed.

docs/api.rst

@@ -52,6 +52,15 @@ Statsd Implementation
 .. autoclass:: sprockets.mixins.metrics.statsd.StatsDCollector
    :members:
 
+Application Functions
+---------------------
+Before you can use the mixin, you have to install the client by calling
+the ``install`` function on your application instance.
+
+.. autofunction:: sprockets.mixins.metrics.statsd.install
+
+.. autofunction:: sprockets.mixins.metrics.statsd.get_client
+
 Testing Helpers
 ---------------
 *So who actually tests that their metrics are emitted as they expect?*

docs/history.rst

@@ -7,6 +7,7 @@ Release History
 ---------------
 - Add configuration documentation
 - Exclude Tornado >6 (as-yet-unreleased version)
+- Add :func:`sprockets.mixins.metrics.statsd.get_client` function
 
 `4.0.0`_ (06-Feb-2019)
 ----------------------

sprockets/mixins/metrics/statsd.py

@@ -29,7 +29,9 @@ class StatsdMixin:
         :param path: elements of the metric path to record
 
         """
-        self.application.statsd.send(path, duration * 1000.0, 'ms')
+        client = get_client(self.application)
+        if client is not None:
+            client.send(path, duration * 1000.0, 'ms')
 
     def increase_counter(self, *path, **kwargs):
         """Increase a counter.
@@ -45,7 +47,9 @@ class StatsdMixin:
             omitted, the counter is increased by one.
 
         """
-        self.application.statsd.send(path, kwargs.get('amount', '1'), 'c')
+        client = get_client(self.application)
+        if client is not None:
+            client.send(path, kwargs.get('amount', '1'), 'c')
 
     @contextlib.contextmanager
     def execution_timer(self, *path):
@@ -227,3 +231,12 @@ def install(application, **kwargs):
 
     setattr(application, 'statsd', StatsDCollector(**kwargs))
     return True
+
+
+def get_client(application):
+    """Fetch the statsd client if it is installed.
+
+    :rtype: .StatsDCollector
+
+    """
+    return getattr(application, 'statsd', None)

tests.py

@@ -162,6 +162,13 @@ class TCPStatsdMetricCollectionTests(testing.AsyncHTTPTestCase):
         response = self.fetch('/status_code')
         self.assertEqual(response.code, 200)
 
+    def test_that_mixin_works_without_client(self):
+        self.application.statsd.close()
+        delattr(self.application, 'statsd')
+
+        response = self.fetch('/', method='POST', body='')
+        self.assertEqual(response.code, 204)
+
 
 class TCPStatsdConfigurationTests(testing.AsyncHTTPTestCase):
 
@@ -308,6 +315,13 @@ class UDPStatsdMetricCollectionTests(testing.AsyncHTTPTestCase):
         self.assertEqual(expected,
                          list(self.statsd.find_metrics(expected, 'ms'))[0][0])
 
+    def test_that_mixin_works_without_client(self):
+        self.application.statsd.close()
+        delattr(self.application, 'statsd')
+
+        response = self.fetch('/', method='POST', body='')
+        self.assertEqual(response.code, 204)
+
 
 class UDPStatsdConfigurationTests(testing.AsyncHTTPTestCase):