Add 'Sink.exists' API wrapper.

gcloud/logging/sink.py

@@ -14,6 +14,8 @@
 
 """Define Logging API Sinks."""
 
+from gcloud.exceptions import NotFound
+
 
 class Sink(object):
     """Sinks represent filtered exports for log entries.
@@ -90,3 +92,22 @@ def create(self, client=None):
             'destination': self.destination,
         }
         client.connection.api_request(method='PUT', path=self.path, data=data)
+
+    def exists(self, client=None):
+        """API call:  test for the existence of the sink via a GET request
+
+        See
+        https://cloud.google.com/logging/docs/api/ref_v2beta1/rest/v2beta1/projects.sinks/get
+
+        :type client: :class:`gcloud.logging.client.Client` or ``NoneType``
+        :param client: the client to use.  If not passed, falls back to the
+                       ``client`` stored on the current sink.
+        """
+        client = self._require_client(client)
+
+        try:
+            client.connection.api_request(method='GET', path=self.path)
+        except NotFound:
+            return False
+        else:
+            return True

gcloud/logging/test_sink.py

@@ -82,6 +82,33 @@ def test_create_w_alternate_client(self):
         self.assertEqual(req['path'], '/%s' % FULL)
         self.assertEqual(req['data'], RESOURCE)
 
+    def test_exists_miss_w_bound_client(self):
+        FULL = 'projects/%s/sinks/%s' % (self.PROJECT, self.SINK_NAME)
+        conn = _Connection()
+        CLIENT = _Client(project=self.PROJECT, connection=conn)
+        sink = self._makeOne(self.SINK_NAME, self.FILTER, self.DESTINATION_URI,
+                             client=CLIENT)
+        self.assertFalse(sink.exists())
+        self.assertEqual(len(conn._requested), 1)
+        req = conn._requested[0]
+        self.assertEqual(req['method'], 'GET')
+        self.assertEqual(req['path'], '/%s' % FULL)
+
+    def test_exists_hit_w_alternate_client(self):
+        FULL = 'projects/%s/sinks/%s' % (self.PROJECT, self.SINK_NAME)
+        conn1 = _Connection({'name': FULL})
+        CLIENT1 = _Client(project=self.PROJECT, connection=conn1)
+        conn2 = _Connection({'name': FULL})
+        CLIENT2 = _Client(project=self.PROJECT, connection=conn2)
+        sink = self._makeOne(self.SINK_NAME, self.FILTER, self.DESTINATION_URI,
+                             client=CLIENT1)
+        self.assertTrue(sink.exists(client=CLIENT2))
+        self.assertEqual(len(conn1._requested), 0)
+        self.assertEqual(len(conn2._requested), 1)
+        req = conn2._requested[0]
+        self.assertEqual(req['method'], 'GET')
+        self.assertEqual(req['path'], '/%s' % FULL)
+
 
 class _Connection(object):