gistfile1.diff

diff --git a/swift/common/storage_policy.py b/swift/common/storage_policy.py
index a0c2cd1..c3ae546 100644
--- a/swift/common/storage_policy.py
+++ b/swift/common/storage_policy.py
@@ -420,13 +420,14 @@ class ECStoragePolicy(StoragePolicy):
         NB: a fragment archive is a sequence of 0 or more max-length
         fragments followed by one possibly-shorter fragment.
         """
-        if self._fragment_header_len is None:
-            # this header is a fixed size, so it's perfectly okay to learn
-            # it by encoding some dummy data
-            self._fragment_header_len = len(self.pyeclib_driver.encode("")[0])
-
-        return (
-            self.ec_segment_size // self._ec_ndata + self._fragment_header_len)
+        # it is not clear why this is the correct call signature to get the
+        # answer we need.  It calls for (data_len, segment_size) but on a
+        # ranged GET we don't know the ec-content-length header before we need
+        # to compute where in the object we should request to align with the
+        # fragment size.  So we tell pyeclib a lie - and it gives us the
+        # number we want - but only sam and kevin might know why this "works".
+        return self.pyeclib_driver.get_segment_info(
+            self.ec_segment_size, self.ec_segment_size)['fragment_size']
 
     def decode_fragments(self, frags):
         return self.pyeclib_driver.decode(frags)