.

lib/tests/test_zodb.py

@@ -234,5 +234,7 @@ def test_zconn_at():
 
     # TODO zconn_at for historic connection
 
+    # TODO zconn_at after empty commit (with fs1 currently gives future tid,
+    # but db is not updated and wcfs client resync to that future tid hangs)
 
     pass

lib/zodb.py

@@ -145,6 +145,8 @@ def zconn_at(zconn): # -> tid
 
     # ZODB5 uses MVCC uniformly
     if zmajor >= 5:
+        # FIXME gives future tid with fs1 and empty commit which leads to wcfs client resync hang
+        # (test_bigfile_filezodb_fmt_change hangs)
         zstor = zconn._storage
         if isinstance(zstor, ZODB.mvccadapter.MVCCAdapterInstance):
             # XXX there is race in ZODB itself that leads to data corruption: