.

lib/tests/test_zodb.py

@@ -230,13 +230,7 @@ def test_deactivate_btree():
             assert obj not in cached
 
 
-# zsync syncs ZODB storage.
-# it is noop, if zstor does not support syncing (i.e. FileStorage has no .sync())
-def zsync(zstor):
-    sync = getattr(zstor, 'sync', None)
-    if sync is not None:
-        sync()
-
+# verify that zconn_at gives correct answer.
 @func
 def test_zconn_at():
     stor = testdb.getZODBStorage()
@@ -256,7 +250,7 @@ def test_zconn_at():
     conn2 = db.open(transaction_manager=tm2)
     assert zconn_at(conn2) == at0
 
-    # commit
+    # commit in conn1
     root1 = conn1.root()
     root1['z'] = 1
     tm1.commit()
@@ -279,9 +273,6 @@ def test_zconn_at():
     conn1.close()
 
     # commit empty transaction - view stays in sync with storage head
-    #
-    # 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)
     conn1_ = db.open(transaction_manager=tm1)
     assert conn1_ is conn1   # from DB pool
     assert zconn_at(conn1) == at1
@@ -305,9 +296,21 @@ def test_zconn_at():
     conn2.close()
 
 
-    # TODO commit -> know head -> open conn1,
-    #      open conn2, commit there; wait or sync, make sure zconn_at(conn1) is as expected
+    # verify with historic connection @at0
+    tm_old = TransactionManager()
+    defer(tm_old.abort)
+    conn_at0 = db.open(transaction_manager=tm_old, at=at0)
+    assert conn_at0 is not conn1
+    assert conn_at0 is not conn2
+    assert zconn_at(conn_at0) == at0
+
 
-    # TODO zconn_at for historic connection
+# ---- misc ----
+
+# zsync syncs ZODB storage.
+# it is noop, if zstor does not support syncing (i.e. FileStorage has no .sync())
+def zsync(zstor):
+    sync = getattr(zstor, 'sync', None)
+    if sync is not None:
+        sync()
 
-    pass

lib/zodb.py

@@ -147,12 +147,8 @@ def zconn_at(zconn): # -> tid
 
     # ZODB5 uses MVCC uniformly
     if zmajor >= 5:
-        # XXX gives future tid with fs1 and empty commit which leads to wcfs client resync hang
-        # -> fixed with https://github.com/zopefoundation/ZODB/pull/298
         zstor = zconn._storage
         if isinstance(zstor, ZODB.mvccadapter.MVCCAdapterInstance):
-            # XXX there is race in ZODB itself that leads to data corruption:
-            # https://github.com/zopefoundation/ZODB/issues/290
             return before2at(zstor._start)
 
         if isinstance(zstor, ZODB.mvccadapter.HistoricalStorageAdapter):

setup.py

@@ -323,6 +323,12 @@ setup(
                    # ( NOTE: ZODB3 3.11 just pulls in latest ZODB _4_, so this way
                    #   specifying ZODB _3_ we allow external requirements to
                    #   specify either to use e.g. ZODB3.10 or ZODB4 )
+                   #
+                   # TODO if ZODB5: require ZODB >= 5.5.2 ?
+                   #    https://github.com/zopefoundation/ZODB/pull/298
+                   #    https://github.com/zopefoundation/ZODB/pull/291
+                   #
+                   # ----//---- for ZODB4 >= 4.4.6
                    'ZODB3 >= 3.10',
 
                    'pygolang >= 0.0.6', # defer, sync.WaitGroup, pyx/nogil channels ... XXX >= 0.0.7