creating a Ring will ensure a valid HASH_PATH_SUFFIX

To make sure that node lookups match what the servers return the generated
hashes need to match.  All the utils that use the ring should validate their
HASH_PATH_SUFFIX.

swift/common/ring/ring.py

@@ -18,7 +18,7 @@ from gzip import GzipFile
 from os.path import getmtime
 from struct import unpack_from
 from time import time
-from swift.common.utils import hash_path
+from swift.common.utils import hash_path, validate_configuration
 
 
 class RingData(object):
@@ -39,6 +39,8 @@ class Ring(object):
     """
 
     def __init__(self, pickle_gz_path, reload_time=15):
+        # can't use the ring unless HASH_PATH_SUFFIX is set
+        validate_configuration()
         self.pickle_gz_path = pickle_gz_path
         self.reload_time = reload_time
         self._reload(force=True)

test/unit/common/ring/test_ring.py

@@ -69,6 +69,13 @@ class TestRing(unittest.TestCase):
         self.assertEquals(self.ring.devs, self.intended_devs)
         self.assertEquals(self.ring.reload_time, self.intended_reload_time)
         self.assertEquals(self.ring.pickle_gz_path, self.testgz)
+        # test invalid endcap
+        _orig_hash_path_suffix = utils.HASH_PATH_SUFFIX
+        try:
+            utils.HASH_PATH_SUFFIX = ''
+            self.assertRaises(SystemExit, ring.Ring, self.testgz)
+        finally:
+            utils.HASH_PATH_SUFFIX = _orig_hash_path_suffix
 
     def test_has_changed(self):
         self.assertEquals(self.ring.has_changed(), False)