(Hopefully) stop leaking file descriptors in media repo. (#9497)

By consuming the response if the headers imply that the
content is too large.

tests/http/test_client.py

@@ -26,77 +26,96 @@ from tests.unittest import TestCase
 
 
 class ReadBodyWithMaxSizeTests(TestCase):
-    def setUp(self):
+    def _build_response(self, length=UNKNOWN_LENGTH):
         """Start reading the body, returns the response, result and proto"""
-        response = Mock(length=UNKNOWN_LENGTH)
-        self.result = BytesIO()
-        self.deferred = read_body_with_max_size(response, self.result, 6)
+        response = Mock(length=length)
+        result = BytesIO()
+        deferred = read_body_with_max_size(response, result, 6)
 
         # Fish the protocol out of the response.
-        self.protocol = response.deliverBody.call_args[0][0]
-        self.protocol.transport = Mock()
+        protocol = response.deliverBody.call_args[0][0]
+        protocol.transport = Mock()
 
-    def _cleanup_error(self):
+        return result, deferred, protocol
+
+    def _assert_error(self, deferred, protocol):
+        """Ensure that the expected error is received."""
+        self.assertIsInstance(deferred.result, Failure)
+        self.assertIsInstance(deferred.result.value, BodyExceededMaxSize)
+        protocol.transport.abortConnection.assert_called_once()
+
+    def _cleanup_error(self, deferred):
         """Ensure that the error in the Deferred is handled gracefully."""
         called = [False]
 
         def errback(f):
             called[0] = True
 
-        self.deferred.addErrback(errback)
+        deferred.addErrback(errback)
         self.assertTrue(called[0])
 
     def test_no_error(self):
         """A response that is NOT too large."""
+        result, deferred, protocol = self._build_response()
 
         # Start sending data.
-        self.protocol.dataReceived(b"12345")
+        protocol.dataReceived(b"12345")
         # Close the connection.
-        self.protocol.connectionLost(Failure(ResponseDone()))
+        protocol.connectionLost(Failure(ResponseDone()))
 
-        self.assertEqual(self.result.getvalue(), b"12345")
-        self.assertEqual(self.deferred.result, 5)
+        self.assertEqual(result.getvalue(), b"12345")
+        self.assertEqual(deferred.result, 5)
 
     def test_too_large(self):
         """A response which is too large raises an exception."""
+        result, deferred, protocol = self._build_response()
 
         # Start sending data.
-        self.protocol.dataReceived(b"1234567890")
-        # Close the connection.
-        self.protocol.connectionLost(Failure(ResponseDone()))
+        protocol.dataReceived(b"1234567890")
 
-        self.assertEqual(self.result.getvalue(), b"1234567890")
-        self.assertIsInstance(self.deferred.result, Failure)
-        self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
-        self._cleanup_error()
+        self.assertEqual(result.getvalue(), b"1234567890")
+        self._assert_error(deferred, protocol)
+        self._cleanup_error(deferred)
 
     def test_multiple_packets(self):
-        """Data should be accummulated through mutliple packets."""
+        """Data should be accumulated through mutliple packets."""
+        result, deferred, protocol = self._build_response()
 
         # Start sending data.
-        self.protocol.dataReceived(b"12")
-        self.protocol.dataReceived(b"34")
+        protocol.dataReceived(b"12")
+        protocol.dataReceived(b"34")
         # Close the connection.
-        self.protocol.connectionLost(Failure(ResponseDone()))
+        protocol.connectionLost(Failure(ResponseDone()))
 
-        self.assertEqual(self.result.getvalue(), b"1234")
-        self.assertEqual(self.deferred.result, 4)
+        self.assertEqual(result.getvalue(), b"1234")
+        self.assertEqual(deferred.result, 4)
 
     def test_additional_data(self):
         """A connection can receive data after being closed."""
+        result, deferred, protocol = self._build_response()
 
         # Start sending data.
-        self.protocol.dataReceived(b"1234567890")
-        self.assertIsInstance(self.deferred.result, Failure)
-        self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
-        self.protocol.transport.abortConnection.assert_called_once()
+        protocol.dataReceived(b"1234567890")
+        self._assert_error(deferred, protocol)
 
         # More data might have come in.
-        self.protocol.dataReceived(b"1234567890")
-        # Close the connection.
-        self.protocol.connectionLost(Failure(ResponseDone()))
+        protocol.dataReceived(b"1234567890")
 
-        self.assertEqual(self.result.getvalue(), b"1234567890")
-        self.assertIsInstance(self.deferred.result, Failure)
-        self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
-        self._cleanup_error()
+        self.assertEqual(result.getvalue(), b"1234567890")
+        self._assert_error(deferred, protocol)
+        self._cleanup_error(deferred)
+
+    def test_content_length(self):
+        """The body shouldn't be read (at all) if the Content-Length header is too large."""
+        result, deferred, protocol = self._build_response(length=10)
+
+        # Deferred shouldn't be called yet.
+        self.assertFalse(deferred.called)
+
+        # Start sending data.
+        protocol.dataReceived(b"12345")
+        self._assert_error(deferred, protocol)
+        self._cleanup_error(deferred)
+
+        # The data is never consumed.
+        self.assertEqual(result.getvalue(), b"")