Merge pull request #7 from dave-shawley/sprockets-http

Detect sprockets.http and make use of it.

CHANGELOG.rst

@@ -1,6 +1,9 @@
 :tag:`Next release <0.0.1...main>`
 ----------------------------------
 - Added :envvar:`STATSD_ENABLED` environment variable to disable the Tornado integration
+- Tornado application mixin automatically installs start/stop hooks if the application
+  quacks like a ``sprockets.http.app.Application``.
+- Limit logging when disconnected from statsd
 
 :tag:`0.0.1 <832f8af7...0.0.1>` (08-Apr-2021)
 ---------------------------------------------

README.rst

@@ -115,6 +115,42 @@ Metrics are sent by a ``asyncio.Task`` that is started by ``start_statsd``.  The
 metric data onto a ``asyncio.Queue`` that the task reads from.  Metric data remains on the queue when the task is
 not connected to the server and will be sent in the order received when the task establishes the server connection.
 
+Integration with sprockets.http
+===============================
+If you use `sprockets.http`_ in your application stack, then the Tornado integration will detect it and install the
+initialization and shutdown hooks for you.  The application will *just work* provided that the `$STATSD_HOST`
+and `$STATSD_PREFIX` environment variables are set appropriately.  The following snippet will produce the same result
+as the Tornado example even without setting the prefix:
+
+.. code-block:: python
+
+   class Application(sprockets_statsd.tornado.Application,
+                     sprockets.http.app.Application):
+       def __init__(self, **settings):
+           statsd = settings.setdefault('statsd', {})
+           statsd.setdefault('host', os.environ['STATSD_HOST'])
+           statsd.setdefault('protocol', 'tcp')
+           settings.update({
+               'service': 'my-service',
+               'environment': os.environ.get('ENVIRONMENT', 'development'),
+               'statsd': statsd,
+               'version': getattr(__package__, 'version'),
+           })
+           super().__init__([web.url('/', MyHandler)], **settings)
+
+   if __name__ == '__main__':
+       sprockets.http.run(Application, log_config=...)
+
+Definint the ``service`` and ``environment`` in `settings` as above will result in the prefix being set to::
+
+   applications.{self.settings["service"]}.{self.settings["environment"]}
+
+The recommended usage is to:
+
+#. define ``service``, ``environment``, and ``version`` in the settings
+#. explicitly set the ``host`` and ``protocol`` settings in  ``self.settings["statsd"]``
+
+.. _sprockets.http: https://sprocketshttp.readthedocs.io/en/master/
 .. _statsd: https://github.com/statsd/statsd/
 .. _tornado: https://tornadoweb.org/
 

setup.cfg

@@ -41,6 +41,7 @@ dev =
     flake8-import-order==0.18.1
     sphinx==3.5.2
     sphinx-autodoc-typehints==1.11.1
+    sprockets.http==2.2.0
     tornado>=5
     yapf==0.30.0
 readthedocs =

sprockets_statsd/statsd.py

@@ -4,6 +4,47 @@ import socket
 import typing
 
 
+class ThrottleGuard:
+    """Prevent code from executing repeatedly.
+
+    :param threshold: guarding threshold
+
+    This abstraction allows code to execute the first "threshold"
+    times and then only once per "threshold" times afterwards.  Use
+    it to ensure that log statements are continuously written during
+    persistent error conditions.  The goal is to provide regular
+    feedback while limiting the amount of log spam.
+
+    The following snippet will log the first 100 failures and then
+    once every 100 failures thereafter:
+
+    .. code-block:: python
+
+       executions = 0
+       guard = ThrottleGuard(100)
+       for _ in range(1000):
+           if guard.allow_execution():
+               executions += 1
+               logging.info('called %s times instead of %s times',
+                            executions, guard.counter)
+
+    """
+    def __init__(self, threshold: int):
+        self.counter = 0
+        self.threshold = threshold
+
+    def allow_execution(self) -> bool:
+        """Should this execution be allowed?"""
+        self.counter += 1
+        allow = (self.counter < self.threshold
+                 or (self.counter % self.threshold) == 0)
+        return allow
+
+    def reset(self) -> None:
+        """Reset counter after error has resolved."""
+        self.counter = 0
+
+
 class AbstractConnector:
     """StatsD connector that does not send metrics or connect.
 
@@ -137,6 +178,7 @@ class Connector(AbstractConnector):
         self.logger = logging.getLogger(__package__).getChild('Connector')
         self.prefix = f'{prefix}.' if prefix else prefix
         self.processor = Processor(host=host, port=port, **kwargs)
+        self._enqueue_log_guard = ThrottleGuard(100)
         self._processor_task: typing.Optional[asyncio.Task[None]] = None
 
     async def start(self) -> None:
@@ -174,8 +216,10 @@ class Connector(AbstractConnector):
         payload = f'{self.prefix}{path}:{value}|{type_code}'
         try:
             self.processor.enqueue(payload.encode('utf-8'))
+            self._enqueue_log_guard.reset()
         except asyncio.QueueFull:
-            self.logger.warning('statsd queue is full, discarding metric')
+            if self._enqueue_log_guard.allow_execution():
+                self.logger.warning('statsd queue is full, discarding metric')
 
 
 class StatsdProtocol(asyncio.BaseProtocol):
@@ -389,6 +433,7 @@ class Processor:
         self.host = host
         self.port = port
         self._ip_protocol = ip_protocol
+        self._connect_log_guard = ThrottleGuard(100)
         self._reconnect_sleep = reconnect_sleep
         self._wait_timeout = wait_timeout
 
@@ -479,14 +524,21 @@ class Processor:
                 buffered_data = b''
                 if self.protocol is not None:
                     buffered_data = self.protocol.buffered_data
+
                 t, p = await self._create_transport()  # type: ignore[misc]
                 transport, self.protocol = t, p
                 self.protocol.buffered_data = buffered_data
-                self.logger.info('connection established to %s',
-                                 transport.get_extra_info('peername'))
+                self.logger.info(
+                    'connection established to %s after %s attempts',
+                    transport.get_extra_info('peername'),
+                    self._connect_log_guard.counter)
+                self._connect_log_guard.reset()
             except IOError as error:
-                self.logger.warning('connection to %s:%s failed: %s',
-                                    self.host, self.port, error)
+                if self._connect_log_guard.allow_execution():
+                    self.logger.warning(
+                        'connection to %s:%s failed: %s (%s attempts)',
+                        self.host, self.port, error,
+                        self._connect_log_guard.counter)
                 await asyncio.sleep(self._reconnect_sleep)
 
     async def _process_metric(self) -> None:

sprockets_statsd/tornado.py

@@ -1,10 +1,11 @@
 import contextlib
+import logging
 import os
 import socket
 import time
 import typing
 
-from tornado import web
+from tornado import ioloop, web
 
 from sprockets_statsd import statsd
 
@@ -114,7 +115,13 @@ class Application(web.Application):
         self.settings['statsd']['port'] = int(self.settings['statsd']['port'])
         self.statsd_connector = None
 
-    async def start_statsd(self) -> None:
+        try:
+            self.on_start_callbacks.append(self.start_statsd)
+            self.on_shutdown_callbacks.append(self.stop_statsd)
+        except AttributeError:
+            pass
+
+    async def start_statsd(self, *_) -> None:
         """Start the connector during startup.
 
         Call this method during application startup to enable the statsd
@@ -124,7 +131,9 @@ class Application(web.Application):
 
         """
         if self.statsd_connector is None:
+            logger = self.__get_logger()
             if not self.settings['statsd']['enabled']:
+                logger.info('statsd connector is disabled by configuration')
                 self.statsd_connector = statsd.AbstractConnector()
             else:
                 kwargs = self.settings['statsd'].copy()
@@ -135,14 +144,20 @@ class Application(web.Application):
                 elif protocol == 'udp':
                     kwargs['ip_protocol'] = socket.IPPROTO_UDP
                 else:
-                    raise RuntimeError(
+                    return self.__handle_fatal_error(
                         f'statsd configuration error: {protocol} is not '
                         f'a valid protocol')
-                self.statsd_connector = statsd.Connector(**kwargs)
+
+                logger.info('creating %s statsd connector', protocol.upper())
+                try:
+                    self.statsd_connector = statsd.Connector(**kwargs)
+                except RuntimeError as error:
+                    return self.__handle_fatal_error(
+                        'statsd.Connector failed to start', error)
 
             await self.statsd_connector.start()
 
-    async def stop_statsd(self) -> None:
+    async def stop_statsd(self, *_) -> None:
         """Stop the connector during shutdown.
 
         If the connector was started, then this method will gracefully
@@ -154,6 +169,26 @@ class Application(web.Application):
             await self.statsd_connector.stop()
             self.statsd_connector = None
 
+    def __handle_fatal_error(self,
+                             message: str,
+                             exc: typing.Optional[Exception] = None):
+        logger = self.__get_logger()
+        if exc is not None:
+            logger.exception('%s', message)
+        else:
+            logger.error('%s', message)
+        if hasattr(self, 'stop'):
+            self.stop(ioloop.IOLoop.current())
+        else:
+            raise RuntimeError(message)
+
+    def __get_logger(self) -> logging.Logger:
+        try:
+            return getattr(self, 'logger')
+        except AttributeError:
+            return logging.getLogger(__package__).getChild(
+                'tornado.Application')
+
 
 class RequestHandler(web.RequestHandler):
     """Mix this into your handler to send metrics to a statsd server."""

tests/test_processor.py

@@ -3,6 +3,7 @@ import logging
 import socket
 import time
 import typing
+import unittest.mock
 
 import asynctest
 
@@ -203,6 +204,17 @@ class TCPProcessingTests(ProcessorTestCase):
         self.processor.queue.put_nowait(b'counter:1|c')
         await self.wait_for(self.statsd_server.message_received.acquire())
 
+    async def test_that_disconnected_logging_is_throttled(self):
+        self.statsd_server.close()
+        await self.statsd_server.wait_closed()
+
+        self.processor.logger = unittest.mock.Mock()
+        self.processor._connect_log_guard.threshold = 10
+        self.processor._reconnect_sleep = 0
+        while self.processor._connect_log_guard.counter < (20 + 1):
+            await asyncio.sleep(0)
+        self.assertLess(self.processor.logger.warning.call_count, 20)
+
 
 class UDPProcessingTests(ProcessorTestCase):
     ip_protocol = socket.IPPROTO_UDP
@@ -354,6 +366,23 @@ class ConnectorTests(ProcessorTestCase):
             self.assertEqual(f'counters.counter:{value}|c'.encode(),
                              self.statsd_server.metrics.pop(0))
 
+    async def test_that_queue_full_logging_is_throttled(self):
+        await self.connector.processor.stop()
+
+        self.connector.logger = unittest.mock.Mock()
+        self.connector._enqueue_log_guard.threshold = 10
+
+        # fill up the queue
+        for _ in range(self.connector.processor.queue.maxsize):
+            self.connector.incr('counter')
+
+        # then overflow it a bunch of times
+        overflow_count = self.connector._enqueue_log_guard.threshold * 5
+        for _ in range(overflow_count):
+            self.connector.incr('counter')
+        self.assertLess(self.connector.logger.warning.call_count,
+                        overflow_count)
+
 
 class ConnectorOptionTests(ProcessorTestCase):
     ip_protocol = socket.IPPROTO_TCP

tests/test_tornado.py

@@ -3,7 +3,10 @@ import os
 import socket
 import time
 import typing
+import unittest.mock
 
+import sprockets.http.app
+import sprockets.http.testing
 from tornado import testing, web
 
 import sprockets_statsd.statsd
@@ -255,30 +258,30 @@ class ApplicationTests(AsyncTestCaseWithTimeout):
                               sprockets_statsd.statsd.AbstractConnector)
 
 
-class RequestHandlerTests(AsyncTestCaseWithTimeout, testing.AsyncHTTPTestCase):
-    def setUp(self):
-        super().setUp()
-        self.statsd_server = helpers.StatsdServer(socket.IPPROTO_TCP)
-        self.io_loop.spawn_callback(self.statsd_server.run)
-        self.run_coroutine(self.statsd_server.wait_running())
+class StatsdTestCase(AsyncTestCaseWithTimeout, testing.AsyncHTTPTestCase):
+    Application = web.Application
 
-        self.app.settings['statsd'].update({
-            'host': self.statsd_server.host,
-            'port': self.statsd_server.port,
-        })
-        self.run_coroutine(self.app.start_statsd())
+    def setUp(self):
+        self.statsd_server = None
+        super().setUp()
 
     def tearDown(self):
-        self.run_coroutine(self.app.stop_statsd())
-        self.statsd_server.close()
-        self.run_coroutine(self.statsd_server.wait_closed())
+        if self.statsd_server is not None:
+            self.statsd_server.close()
+            self.run_coroutine(self.statsd_server.wait_closed())
         super().tearDown()
 
     def get_app(self):
-        self.app = Application(statsd={
-            'prefix': 'applications.service',
-            'protocol': 'tcp',
-        })
+        self.statsd_server = helpers.StatsdServer(socket.IPPROTO_TCP)
+        self.io_loop.spawn_callback(self.statsd_server.run)
+        self.run_coroutine(self.statsd_server.wait_running())
+        self.app = self.Application(shutdown_limit=0.5,
+                                    statsd={
+                                        'host': self.statsd_server.host,
+                                        'port': self.statsd_server.port,
+                                        'prefix': 'applications.service',
+                                        'protocol': 'tcp',
+                                    })
         return self.app
 
     def wait_for_metrics(self, metric_count=3):
@@ -310,6 +313,19 @@ class RequestHandlerTests(AsyncTestCaseWithTimeout, testing.AsyncHTTPTestCase):
                 return self.parse_metric(line)
         self.fail(f'failed to find metric containing {needle!r}')
 
+
+class RequestHandlerTests(StatsdTestCase, AsyncTestCaseWithTimeout,
+                          testing.AsyncHTTPTestCase):
+    Application = Application
+
+    def setUp(self):
+        super().setUp()
+        self.run_coroutine(self.app.start_statsd())
+
+    def tearDown(self):
+        self.run_coroutine(self.app.stop_statsd())
+        super().tearDown()
+
     def test_the_request_metric_is_sent_last(self):
         rsp = self.fetch('/')
         self.assertEqual(200, rsp.code)
@@ -343,3 +359,37 @@ class RequestHandlerTests(AsyncTestCaseWithTimeout, testing.AsyncHTTPTestCase):
 
         rsp = self.fetch('/')
         self.assertEqual(200, rsp.code)
+
+
+class SprocketsHttpInteropTests(StatsdTestCase, AsyncTestCaseWithTimeout,
+                                sprockets.http.testing.SprocketsHttpTestCase):
+    class Application(sprockets_statsd.tornado.Application,
+                      sprockets.http.app.Application):
+        def __init__(self, **settings):
+            super().__init__([web.url('/', Handler)], **settings)
+
+    def setUp(self):
+        super().setUp()
+        self.let_callbacks_run()
+
+    def let_callbacks_run(self):
+        self.io_loop.run_sync(lambda: asyncio.sleep(0))
+
+    def test_that_callbacks_are_installed(self):
+        self.assertIn(self.app.start_statsd, self.app.on_start_callbacks)
+        self.assertIn(self.app.stop_statsd, self.app.on_shutdown_callbacks)
+
+    def test_that_statsd_connector_is_enabled(self):
+        # verifies that the start callback actually runs correctly.
+        self.assertIsNotNone(self.app.statsd_connector,
+                             'statsd_connecter was never created')
+
+    def test_that_misconfiguration_stops_application(self):
+        another_app = self.Application(statsd={
+            'host': '',
+            'prefix': 'whatever',
+        })
+        another_app.stop = unittest.mock.Mock(wraps=another_app.stop)
+        another_app.start(self.io_loop)
+        self.let_callbacks_run()
+        another_app.stop.assert_called_once_with(self.io_loop)