Remove double GET on range requests.

The proxy server's ObjectController was performing multiple GET
requests to the object server when processing requests with Range
headers. This was a workaround for a bug in the proxy server's
Controller.GETorHEAD_base method where a response code of 416 from the
object server was incorrectly treated as a bad response from the
backend, the same way a 404 or a 5xx would be.

A 416 (Requested Range Not Satisfiable) from the object server is now
considered a good response. Since the response headers from the object
server already include the X-Object-Manifest header, there's no need
to make a second request (sans Range header) to see if the object is a
manifest.

Bonus fix: updated message for status 416 to match RFC2616.

Bonus fix 2: removed a leftover debugging print() in
test/unit/proxy/test_server.py.

Fixes bug 1065869.

Change-Id: I156af0b463f02ef19a8cfe37092544a599d89b78

swift/common/swob.py

@@ -70,7 +70,7 @@ RESPONSE_REASONS = {
           'server.'),
     415: ('Unsupported Media Type', 'The request media type is not '
           'supported by this server.'),
-    416: ('Request Range Not Satisfiable', 'The Range requested is not '
+    416: ('Requested Range Not Satisfiable', 'The Range requested is not '
           'available.'),
     417: ('Expectation Failed', 'Expectation failed.'),
     422: ('Unprocessable Entity', 'Unable to process the contained '
@@ -271,8 +271,6 @@ def _resp_status_property():
     When set to a str, it splits status_int and title apart.
     When set to an integer, retrieves the correct title for that
     response code from the RESPONSE_REASONS dict.
-
-    :param header: name of the header, e.g. "Content-Length"
     """
     def getter(self):
         return '%s %s' % (self.status_int, self.title)
@@ -383,8 +381,8 @@ def _resp_charset_property():
 def _resp_app_iter_property():
     """
     Set and retrieve Response.app_iter
-    Mostly a pass-through to Response._app_iter, it's a property so it can zero
+    Mostly a pass-through to Response._app_iter; it's a property so it can zero
-    out an exsisting content-length on assignment.
+    out an existing content-length on assignment.
     """
     def getter(self):
         return self._app_iter

swift/proxy/controllers/base.py

@@ -566,6 +566,13 @@ class Controller(object):
         except Exception:
             pass
 
+    def is_good_source(self, src):
+        """
+        Indicates whether or not the request made to the backend found
+        what it was looking for.
+        """
+        return is_success(src.status) or is_redirection(src.status)
+
     def GETorHEAD_base(self, req, server_type, partition, nodes, path,
                        attempts):
         """
@@ -609,8 +616,7 @@ class Controller(object):
                     node, server_type, _('Trying to %(method)s %(path)s') %
                     {'method': req.method, 'path': req.path})
                 continue
-            if is_success(possible_source.status) or \
+            if self.is_good_source(possible_source):
-                    is_redirection(possible_source.status):
                 # 404 if we know we don't have a synced copy
                 if not float(possible_source.getheader('X-PUT-Timestamp', 1)):
                     statuses.append(HTTP_NOT_FOUND)

swift/proxy/controllers/obj.py

@@ -276,6 +276,17 @@ class ObjectController(Controller):
             for obj in sublisting:
                 yield obj
 
+    def is_good_source(self, src):
+        """
+        Indicates whether or not the request made to the backend found
+        what it was looking for.
+
+        In the case of an object, a 416 indicates that we found a
+        backend with the object.
+        """
+        return src.status == 416 or \
+            super(ObjectController, self).is_good_source(src)
+
     def GETorHEAD(self, req):
         """Handle HTTP GET or HEAD requests."""
         container_info = self.container_info(self.account_name,
@@ -285,28 +296,13 @@ class ObjectController(Controller):
             aresp = req.environ['swift.authorize'](req)
             if aresp:
                 return aresp
+
         partition, nodes = self.app.object_ring.get_nodes(
             self.account_name, self.container_name, self.object_name)
         shuffle(nodes)
         resp = self.GETorHEAD_base(req, _('Object'), partition,
                 self.iter_nodes(partition, nodes, self.app.object_ring),
                 req.path_info, len(nodes))
-        # Whether we get a 416 Requested Range Not Satisfiable or not,
-        # we should request a manifest because size of manifest file
-        # can be not 0. After checking a manifest, redo the range request
-        # on the whole object.
-        if req.range:
-            req_range = req.range
-            req.range = None
-            resp2 = self.GETorHEAD_base(req, _('Object'), partition,
-                                        self.iter_nodes(partition,
-                                                        nodes,
-                                                        self.app.object_ring),
-                                        req.path_info, len(nodes))
-            if 'x-object-manifest' not in resp2.headers:
-                return resp
-            resp = resp2
-            req.range = str(req_range)
 
         if 'x-object-manifest' in resp.headers:
             lcontainer, lprefix = \
@@ -367,6 +363,10 @@ class ObjectController(Controller):
                 resp.last_modified = last_modified
                 resp.etag = etag
             resp.headers['accept-ranges'] = 'bytes'
+            # In case of a manifest file of nonzero length, the
+            # backend may have sent back a Content-Range header for
+            # the manifest. It's wrong for the client, though.
+            resp.content_range = None
 
         return resp
 

test/unit/common/test_swob.py

@@ -419,14 +419,14 @@ class TestResponse(unittest.TestCase):
         body = ''.join(resp([], start_response))
         self.assertEquals(body, '')
         self.assertEquals(resp.content_length, 0)
-        self.assertEquals(resp.status, '416 Request Range Not Satisfiable')
+        self.assertEquals(resp.status, '416 Requested Range Not Satisfiable')
 
         resp = swift.common.swob.Response(
             body='1234567890', request=req,
             conditional_response=True)
         body = ''.join(resp([], start_response))
         self.assertEquals(body, '')
-        self.assertEquals(resp.status, '416 Request Range Not Satisfiable')
+        self.assertEquals(resp.status, '416 Requested Range Not Satisfiable')
 
         # Syntactically-invalid Range headers "MUST" be ignored
         req = swift.common.swob.Request.blank(

test/unit/proxy/test_server.py

@@ -1495,7 +1495,6 @@ class TestObjectController(unittest.TestCase):
                                                        'container', 'object')
             self.assert_status_map(controller.HEAD, (200, 200, 503, 200, 200),
                                    200)
-            print controller.app.object_ring.devs
             self.assertEquals(controller.app.object_ring.devs[0]['errors'], 2)
             self.assert_('last_error' in controller.app.object_ring.devs[0])
             for _junk in xrange(self.app.error_suppression_limit):