Add support for disabling tornado connector.

CHANGELOG.rst

@@ -1,5 +1,7 @@
-`0.0.1`_ (08-Apr-2021)
+:tag:`Next release <0.0.1...main>`
-----------------------
+----------------------------------
-- support for sending counters & timers to statsd over a TCP or UDP socket
+- Added :envvar:`STATSD_ENABLED` environment variable to disable the Tornado integration
 
-.. _0.0.1: https://github.com/sprockets/sprockets-statsd/compare/832f8af7...0.0.1
+:tag:`0.0.1 <832f8af7...0.0.1>` (08-Apr-2021)
+---------------------------------------------
+- Simple support for sending counters & timers to statsd over a TCP or UDP socket

docs/conf.py

@@ -16,5 +16,11 @@ intersphinx_mapping = {
     'tornado': ('https://www.tornadoweb.org/en/branch6.0/', None),
 }
 
+# https://www.sphinx-doc.org/en/master/usage/extensions/extlinks.html
+extensions.append('sphinx.ext.extlinks')
+extlinks = {
+    'tag': ("https://github.com/sprockets/sprockets-statsd/compare/%s", "%s"),
+}
+
 # https://pypi.org/project/sphinx-autodoc-typehints/
 extensions.append('sphinx_autodoc_typehints')

docs/index.rst

@@ -3,10 +3,10 @@ sprockets-statsd
 
 .. include:: ../README.rst
 
-Configuration
+Tornado configuration
-=============
+=====================
-The statsd connection is configured by the ``statsd`` application settings key.  The default values can be set by
+The Tornado statsd connection is configured by the ``statsd`` application settings key.  The default values can be set
-the following environment variables.
+by the following environment variables.
 
 .. envvar:: STATSD_HOST
 
@@ -26,6 +26,17 @@ the following environment variables.
    The IP protocol to use when connecting to the StatsD server.  You can specify either "tcp" or "udp".  The
    default is "tcp" if it not not configured.
 
+.. envvar:: STATSD_ENABLED
+
+   Define this variable and set it to a *falsy* value to **disable** the Tornado integration.  If you omit
+   this variable, then the connector is enabled.  The following values are considered *truthy*:
+
+   - non-zero integer
+   - case-insensitive match of ``yes``, ``true``, ``t``, or ``on``
+
+   All other values are considered *falsy*.  You only want to define this environment variables when you
+   want to explicitly disable an otherwise installed and configured connection.
+
 If you are using the Tornado helper clases, then you can fine tune the metric payloads and the connector by
 setting additional values in the ``statsd`` key of :attr:`tornado.web.Application.settings`.  See the
 :class:`sprockets_statsd.tornado.Application` class documentation for a description of the supported settings.
@@ -46,6 +57,9 @@ Tornado helpers
 
 Internals
 ---------
+.. autoclass:: sprockets_statsd.statsd.AbstractConnector
+   :members:
+
 .. autoclass:: sprockets_statsd.statsd.Processor
    :members:
 

setup.cfg

@@ -63,6 +63,7 @@ warning_is_error = 1
 
 [coverage:report]
 exclude_lines =
+    pass
     pragma: no cover
     raise NotImplementedError
 fail_under = 100

sprockets_statsd/statsd.py

@@ -4,7 +4,71 @@ import socket
 import typing
 
 
-class Connector:
+class AbstractConnector:
+    """StatsD connector that does not send metrics or connect.
+
+    Use this connector when you want to maintain the application
+    interface without doing any real work.
+
+    """
+    async def start(self) -> None:
+        pass
+
+    async def stop(self) -> None:
+        pass
+
+    def inject_metric(self, path: str, value: str, type_code: str) -> None:
+        pass
+
+    def incr(self, path: str, value: int = 1) -> None:
+        """Increment a counter metric.
+
+        :param path: counter to increment
+        :param value: amount to increment the counter by
+
+        """
+        self.inject_metric(f'counters.{path}', str(value), 'c')
+
+    def decr(self, path: str, value: int = 1) -> None:
+        """Decrement a counter metric.
+
+        :param path: counter to decrement
+        :param value: amount to decrement the counter by
+
+        This is equivalent to ``self.incr(path, -value)``.
+
+        """
+        self.inject_metric(f'counters.{path}', str(-value), 'c')
+
+    def gauge(self, path: str, value: int, delta: bool = False) -> None:
+        """Manipulate a gauge metric.
+
+        :param path: gauge to adjust
+        :param value: value to send
+        :param delta: is this an adjustment of the gauge?
+
+        If the `delta` parameter is ``False`` (or omitted), then
+        `value` is the new value to set the gauge to.  Otherwise,
+        `value` is an adjustment for the current gauge.
+
+        """
+        if delta:
+            payload = f'{value:+d}'
+        else:
+            payload = str(value)
+        self.inject_metric(f'gauges.{path}', payload, 'g')
+
+    def timing(self, path: str, seconds: float) -> None:
+        """Send a timer metric.
+
+        :param path: timer to append a value to
+        :param seconds: number of **seconds** to record
+
+        """
+        self.inject_metric(f'timers.{path}', str(seconds * 1000.0), 'ms')
+
+
+class Connector(AbstractConnector):
     """Sends metrics to a statsd server.
 
     :param host: statsd server to send metrics to
@@ -69,6 +133,7 @@ class Connector:
                  *,
                  prefix: str = '',
                  **kwargs: typing.Any) -> None:
+        super().__init__()
         self.logger = logging.getLogger(__package__).getChild('Connector')
         self.prefix = f'{prefix}.' if prefix else prefix
         self.processor = Processor(host=host, port=port, **kwargs)
@@ -95,53 +160,6 @@ class Connector:
         """
         await self.processor.stop()
 
-    def incr(self, path: str, value: int = 1) -> None:
-        """Increment a counter metric.
-
-        :param path: counter to increment
-        :param value: amount to increment the counter by
-
-        """
-        self.inject_metric(f'counters.{path}', str(value), 'c')
-
-    def decr(self, path: str, value: int = 1) -> None:
-        """Decrement a counter metric.
-
-        :param path: counter to decrement
-        :param value: amount to decrement the counter by
-
-        This is equivalent to ``self.incr(path, -value)``.
-
-        """
-        self.inject_metric(f'counters.{path}', str(-value), 'c')
-
-    def gauge(self, path: str, value: int, delta: bool = False) -> None:
-        """Manipulate a gauge metric.
-
-        :param path: gauge to adjust
-        :param value: value to send
-        :param delta: is this an adjustment of the gauge?
-
-        If the `delta` parameter is ``False`` (or omitted), then
-        `value` is the new value to set the gauge to.  Otherwise,
-        `value` is an adjustment for the current gauge.
-
-        """
-        if delta:
-            payload = f'{value:+d}'
-        else:
-            payload = str(value)
-        self.inject_metric(f'gauges.{path}', payload, 'g')
-
-    def timing(self, path: str, seconds: float) -> None:
-        """Send a timer metric.
-
-        :param path: timer to append a value to
-        :param seconds: number of **seconds** to record
-
-        """
-        self.inject_metric(f'timers.{path}', str(seconds * 1000.0), 'ms')
-
     def inject_metric(self, path: str, value: str, type_code: str) -> None:
         """Send a metric to the statsd server.
 

sprockets_statsd/tornado.py

@@ -13,7 +13,7 @@ class Application(web.Application):
     """Mix this into your application to add a statsd connection.
 
     .. attribute:: statsd_connector
-       :type: sprockets_statsd.statsd.Connector
+       :type: sprockets_statsd.statsd.AbstractConnector
 
        Connection to the StatsD server that is set between calls
        to :meth:`.start_statsd` and :meth:`.stop_statsd`.
@@ -21,6 +21,8 @@ class Application(web.Application):
     This mix-in is configured by the ``statsd`` settings key.  The
     value is a dictionary with the following keys.
 
+    +-------------------+---------------------------------------------+
+    | enabled           | should the statsd connector be enabled?     |
     +-------------------+---------------------------------------------+
     | host              | the statsd host to send metrics to          |
     +-------------------+---------------------------------------------+
@@ -38,6 +40,13 @@ class Application(web.Application):
     |                   | connection                                  |
     +-------------------+---------------------------------------------+
 
+    **enabled** defaults to the :envvar:`STATSD_ENABLED` environment
+    variable coerced to a :class:`bool`.  If this variable is not set,
+    then the statsd connector *WILL BE* enabled.  Set this to a *falsy*
+    value to disable the connector.  The following values are considered
+    *truthy*: a non-zero integer or a case-insensitive match of "on",
+    "t", "true", or "yes".  All other values are considered *falsy*.
+
     **host** defaults to the :envvar:`STATSD_HOST` environment variable.
     If this value is not set, then the statsd connector *WILL NOT* be
     enabled.
@@ -72,10 +81,12 @@ class Application(web.Application):
     processor quickly responds to connection faults.
 
     """
-    statsd_connector: typing.Optional[statsd.Connector]
+    statsd_connector: typing.Optional[statsd.AbstractConnector]
 
     def __init__(self, *args: typing.Any, **settings: typing.Any):
         statsd_settings = settings.setdefault('statsd', {})
+        statsd_settings.setdefault('enabled',
+                                   os.environ.get('STATSD_ENABLED', 'yes'))
         statsd_settings.setdefault('host', os.environ.get('STATSD_HOST'))
         statsd_settings.setdefault('port',
                                    os.environ.get('STATSD_PORT', '8125'))
@@ -98,6 +109,8 @@ class Application(web.Application):
 
         super().__init__(*args, **settings)
 
+        self.settings['statsd']['enabled'] = _parse_bool(
+            self.settings['statsd']['enabled'])
         self.settings['statsd']['port'] = int(self.settings['statsd']['port'])
         self.statsd_connector = None
 
@@ -111,17 +124,22 @@ class Application(web.Application):
 
         """
         if self.statsd_connector is None:
+            if not self.settings['statsd']['enabled']:
+                self.statsd_connector = statsd.AbstractConnector()
+            else:
                 kwargs = self.settings['statsd'].copy()
+                kwargs.pop('enabled', None)  # consume this one
                 protocol = kwargs.pop('protocol', None)
                 if protocol == 'tcp':
                     kwargs['ip_protocol'] = socket.IPPROTO_TCP
                 elif protocol == 'udp':
                     kwargs['ip_protocol'] = socket.IPPROTO_UDP
                 else:
-                raise RuntimeError(f'statsd configuration error: {protocol} '
+                    raise RuntimeError(
-                                   f'is not a valid protocol')
+                        f'statsd configuration error: {protocol} is not '
-
+                        f'a valid protocol')
                 self.statsd_connector = statsd.Connector(**kwargs)
+
             await self.statsd_connector.start()
 
     async def stop_statsd(self) -> None:
@@ -195,3 +213,10 @@ class RequestHandler(web.RequestHandler):
         self.record_timing(self.request.request_time(),
                            self.__class__.__name__, self.request.method,
                            self.get_status())
+
+
+def _parse_bool(value: str) -> bool:
+    try:
+        return int(value) != 0
+    except ValueError:
+        return value.lower() in {'true', 't', 'yes', 'on'}

tests/test_tornado.py

@@ -6,6 +6,7 @@ import typing
 
 from tornado import testing, web
 
+import sprockets_statsd.statsd
 import sprockets_statsd.tornado
 from tests import helpers
 
@@ -49,21 +50,22 @@ class ApplicationTests(AsyncTestCaseWithTimeout):
             else:
                 os.environ.pop(name, None)
 
-    def setenv(self, name, value):
+    def setenv(self, **variables):
+        for name, value in variables.items():
             self._environ.setdefault(name, os.environ.pop(name, None))
             os.environ[name] = value
 
-    def unsetenv(self, name):
+    def unsetenv(self, *names):
+        for name in names:
             self._environ.setdefault(name, os.environ.pop(name, None))
 
     def test_statsd_setting_defaults(self):
-        self.unsetenv('STATSD_HOST')
+        self.unsetenv('STATSD_ENABLED', 'STATSD_HOST', 'STATSD_PORT',
-        self.unsetenv('STATSD_PORT')
+                      'STATSD_PREFIX', 'STATSD_PROTOCOL')
-        self.unsetenv('STATSD_PREFIX')
-        self.unsetenv('STATSD_PROTOCOL')
 
         app = sprockets_statsd.tornado.Application(statsd={'prefix': ''})
         self.assertIn('statsd', app.settings)
+        self.assertTrue(app.settings['statsd']['enabled'])
         self.assertIsNone(app.settings['statsd']['host'],
                           'default host value should be None')
         self.assertEqual(8125, app.settings['statsd']['port'])
@@ -71,13 +73,15 @@ class ApplicationTests(AsyncTestCaseWithTimeout):
         self.assertEqual('tcp', app.settings['statsd']['protocol'])
 
     def test_that_statsd_settings_read_from_environment(self):
-        self.setenv('STATSD_HOST', 'statsd')
+        self.setenv(STATSD_ENABLED='no',
-        self.setenv('STATSD_PORT', '5218')
+                    STATSD_HOST='statsd',
-        self.setenv('STATSD_PREFIX', 'my-service')
+                    STATSD_PORT='5218',
-        self.setenv('STATSD_PROTOCOL', 'udp')
+                    STATSD_PREFIX='my-service',
+                    STATSD_PROTOCOL='udp')
 
         app = sprockets_statsd.tornado.Application()
         self.assertIn('statsd', app.settings)
+        self.assertFalse(app.settings['statsd']['enabled'])
         self.assertEqual('statsd', app.settings['statsd']['host'])
         self.assertEqual(5218, app.settings['statsd']['port'])
         self.assertEqual('my-service', app.settings['statsd']['prefix'])
@@ -99,18 +103,22 @@ class ApplicationTests(AsyncTestCaseWithTimeout):
                          app.settings['statsd']['prefix'])
 
     def test_overridden_settings(self):
-        self.setenv('STATSD_HOST', 'statsd')
+        self.setenv(STATSD_ENABLED='0',
-        self.setenv('STATSD_PORT', '9999')
+                    STATSD_HOST='statsd',
-        self.setenv('STATSD_PREFIX', 'service')
+                    STATSD_PORT='9999',
-        self.setenv('STATSD_PROTOCOL', 'tcp')
+                    STATSD_PREFIX='service',
+                    STATSD_PROTOCOL='tcp')
+
         app = sprockets_statsd.tornado.Application(
             statsd={
+                'enabled': 'true',
                 'host': 'statsd.example.com',
                 'port': 5218,
                 'prefix': 'myapp',
                 'protocol': 'udp',
             })
         self.assertEqual('statsd.example.com', app.settings['statsd']['host'])
+        self.assertTrue(app.settings['statsd']['enabled'])
         self.assertEqual(5218, app.settings['statsd']['port'])
         self.assertEqual('myapp', app.settings['statsd']['prefix'])
         self.assertEqual('udp', app.settings['statsd']['protocol'])
@@ -231,6 +239,21 @@ class ApplicationTests(AsyncTestCaseWithTimeout):
         self.assertEqual(app.statsd_connector.prefix, '')
         self.run_coroutine(app.stop_statsd())
 
+    def test_disabling_statsd_connector(self):
+        app = sprockets_statsd.tornado.Application(
+            environment='development',
+            service='my-service',
+            version='1.0.0',
+            statsd={
+                'enabled': 'no',
+                'host': 'localhost',
+            },
+        )
+        self.run_coroutine(app.start_statsd())
+        self.assertIsNotNone(app.statsd_connector)
+        self.assertIsInstance(app.statsd_connector,
+                              sprockets_statsd.statsd.AbstractConnector)
+
 
 class RequestHandlerTests(AsyncTestCaseWithTimeout, testing.AsyncHTTPTestCase):
     def setUp(self):