Fix download resumption for new SLOs.

SLOs created after commit 2d25fe6ad3
have an explicit X-Object-Sysmeta-SLO-Size attribute. Fetching one of
those with a range like "bytes=100-" would crash and cause a 500. This
commit fixes the crash.

Closes-Bug: #1656147

Change-Id: I174ed98b4f01a5943af12177d6f8c3586f049778

swift/common/middleware/slo.py

@@ -703,7 +703,9 @@ class SloGetContext(WSGIContext):
             if lheader == SYSMETA_SLO_ETAG:
                 slo_etag = value
             elif lheader == SYSMETA_SLO_SIZE:
-                content_length = value
+                # it's from sysmeta, so we don't worry about non-integer
+                # values here
+                content_length = int(value)
             elif lheader not in ('etag', 'content-length'):
                 response_headers.append((header, value))
 

test/functional/test_slo.py

@@ -354,6 +354,33 @@ class TestSlo(Base):
         self.assertEqual('b', file_contents[-2])
         self.assertEqual('c', file_contents[-1])
 
+    def test_slo_ranged_get_half_open_on_right(self):
+        file_item = self.env.container.file('manifest-abcde')
+        file_contents = file_item.read(
+            hdrs={"Range": "bytes=1048571-"})
+        grouped_file_contents = [
+            (char, sum(1 for _char in grp))
+            for char, grp in itertools.groupby(file_contents)]
+        self.assertEqual([
+            ('a', 5),
+            ('b', 1048576),
+            ('c', 1048576),
+            ('d', 1048576),
+            ('e', 1)
+        ], grouped_file_contents)
+
+    def test_slo_ranged_get_half_open_on_left(self):
+        file_item = self.env.container.file('manifest-abcde')
+        file_contents = file_item.read(
+            hdrs={"Range": "bytes=-123456"})
+        grouped_file_contents = [
+            (char, sum(1 for _char in grp))
+            for char, grp in itertools.groupby(file_contents)]
+        self.assertEqual([
+            ('d', 123455),
+            ('e', 1),
+        ], grouped_file_contents)
+
     def test_slo_multi_ranged_get(self):
         file_item = self.env.container.file('manifest-abcde')
         file_contents = file_item.read(

test/unit/common/middleware/test_slo.py

@@ -3017,6 +3017,16 @@ class TestSloConditionalGetOldManifest(SloTestCase):
         self.assertNotIn('X-Backend-Etag-Is-At', self.app.headers[0])
         self.assertNotIn('X-Backend-Etag-Is-At', self.app.headers[1])
 
+    def test_range_resume_download(self):
+        req = Request.blank(
+            '/v1/AUTH_test/gettest/manifest-abcd',
+            environ={'REQUEST_METHOD': 'GET'},
+            headers={'Range': 'bytes=20-'})
+        status, headers, body = self.call_slo(req)
+
+        self.assertEqual(status, '206 Partial Content')
+        self.assertEqual(body, 'ccccccccccdddddddddddddddddddd')
+
 
 class TestSloConditionalGetNewManifest(TestSloConditionalGetOldManifest):
     def setUp(self):