Add an additional comment on the data verification.

git-svn-id: https://svn.erp5.org/repos/neo/branches/prototype3@33 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/master/app.py

@@ -512,6 +512,21 @@ class Application(object):
                         conn.addPacket(p)
             
         # Gather all unfinished transactions.
+        # 
+        # FIXME this part requires more brainstorming. Currently, this deals with
+        # only unfinished transactions. But how about finished transactions?
+        # Suppose that A and B have an unfinished transaction. First, A and B are
+        # asked to commit the transaction. Then, A succeeds. B gets down. Now,
+        # A believes that the transaction has been committed, while B still believes
+        # that the transaction is unfinished. Next, if B goes back and A is working,
+        # no problem; because B's unfinished transaction will be committed correctly.
+        # However, when B goes back, if A is down, what happens? If the state is
+        # not very good, B may be asked to abort the transaction!
+        # 
+        # This situation won't happen frequently, and B shouldn't be asked to drop
+        # the transaction, if the cluster is not ready. However, there might be
+        # some corner cases where this may happen. That's why more brainstorming
+        # is required.
         self.asking_uuid_dict = {}
         self.unfinished_tid_set = set()
         for conn in em.getConnectionList():