Fix a socket leak in copy middleware

When the "copy" middleware tries to copy a segmented object which is
bigger than max_file_size, it immediatly returns "413 Request Entity Too
Large". But at that point, connections have already been established by
the proxy server to the object servers. These connections must be closed
before returning.

Closes-Bug: #1698207
Change-Id: I430c48c4a81e8392fa271160bcbc1817ef0a88f7

swift/common/middleware/copy.py

@@ -413,9 +413,11 @@ class ServerSideCopyMiddleware(object):
             # which currently only happens because there are more than
             # CONTAINER_LISTING_LIMIT segments in a segmented object. In
             # this case, we're going to refuse to do the server-side copy.
+            close_if_possible(source_resp.app_iter)
             return HTTPRequestEntityTooLarge(request=req)
 
         if source_resp.content_length > MAX_FILE_SIZE:
+            close_if_possible(source_resp.app_iter)
             return HTTPRequestEntityTooLarge(request=req)
 
         return source_resp
@@ -459,7 +461,6 @@ class ServerSideCopyMiddleware(object):
         ssc_ctx = ServerSideCopyWebContext(self.app, self.logger)
         source_resp = self._get_source_object(ssc_ctx, source_path, req)
         if source_resp.status_int >= HTTP_MULTIPLE_CHOICES:
-            close_if_possible(source_resp.app_iter)
             return source_resp(source_resp.environ, start_response)
 
         # Create a new Request object based on the original request instance.

test/unit/common/middleware/test_copy.py

@@ -27,6 +27,7 @@ from swift.common import swob
 from swift.common.middleware import copy
 from swift.common.storage_policy import POLICIES
 from swift.common.swob import Request, HTTPException
+from swift.common.utils import closing_if_possible
 from test.unit import patch_policies, debug_logger, FakeMemcache, FakeRing
 from test.unit.common.middleware.helpers import FakeSwift
 from test.unit.proxy.controllers.test_obj import set_http_connect, \
@@ -97,6 +98,9 @@ class TestServerSideCopyMiddleware(unittest.TestCase):
         })(self.app)
         self.ssc.logger = self.app.logger
 
+    def tearDown(self):
+        self.assertEqual(self.app.unclosed_requests, {})
+
     def call_app(self, req, app=None, expect_exception=False):
         if app is None:
             app = self.app
@@ -122,8 +126,10 @@ class TestServerSideCopyMiddleware(unittest.TestCase):
         body = ''
         caught_exc = None
         try:
-            for chunk in body_iter:
-                body += chunk
+            # appease the close-checker
+            with closing_if_possible(body_iter):
+                for chunk in body_iter:
+                    body += chunk
         except Exception as exc:
             if expect_exception:
                 caught_exc = exc