master: simplify verification by ignoring completely nodes without readable cells

The scenario that was described in comments was meaningless
because S1 never goes out-of-date.

neo/master/verification.py

@@ -66,7 +66,7 @@ class VerificationManager(BaseServiceHandler):
         # - there's no unfinished data
         # - just before they return the last tid/oid
         self._askStorageNodesAndWait(Packets.AskLastIDs(),
-            [x for x in app.nm.getIdentifiedList() if x.isStorage()])
+            app.nm.getStorageList(only_identified=True))
         app.setLastTransaction(app.tm.getLastTID())
         # Just to not return meaningless information in AnswerRecovery.
         app.truncate_tid = None
@@ -78,28 +78,21 @@ class VerificationManager(BaseServiceHandler):
 
         # Gather all transactions that may have been partially finished.
         # It's safe to query outdated cells from nodes with readable cells.
-        # For other nodes, it's more complicated:
-        #  1. pt: U|U  ltid: 10
+        # On the other hand, we must ignore temporary data from other nodes:
+        #  1. S1:U  S2:U  ltid:10
         #  2. S1: restart with voted ttid=13
         #     S2: stop with locked ttid=13
-        #  3. pt: U|O  ltid: 10
+        #  3. S1:U  S2:O  ltid:10
         #  4. verification drops ttid=13 because it's not locked
-        #  5. new commits -> ltid: 20
+        #  5. new commits -> ltid:20
         #  6. S1 restarted, S2 started
         #  7. ttid=13 must be dropped
-        # And we can't ignore ttid < last tid for all nodes, even if the
-        # master serializes unlock notifications:
-        #  1. pt: U.|.U  ltid: 15
-        #  2. unlock ttid=18 to S1
-        #  3. unlock ttid=20 to S2
-        #  4. S1 stopped before unlocking ttid=18
-        #  5. S2 unlocks ttid=20
-        #  6. back to recovery, S1 started
-        #  7. verification must validate ttid=18
-        # So for nodes without any readable cell, and only for them, we only
-        # check if they have locked transactions. Replication will do the rest.
-        self._askStorageNodesAndWait(Packets.AskLockedTransactions(),
-            [x for x in getIdentifiedList() if x.isStorage()])
+        # Replication will fix them if the data should have been validated.
+        # And in the case such node had information about locked transactions,
+        # a node with readable cells would have unlocked them.
+        node_set = app.pt.getNodeSet(readable=True)
+        assert all(node.isIdentified() for node in node_set), node_set
+        self._askStorageNodesAndWait(Packets.AskLockedTransactions(), node_set)
 
         # Some nodes may have already unlocked these transactions and
         # _locked_dict is incomplete, but we can ask them the final tid.
@@ -142,13 +135,9 @@ class VerificationManager(BaseServiceHandler):
     def answerLockedTransactions(self, conn, tid_dict):
         uuid = conn.getUUID()
         self._uuid_set.remove(uuid)
-        app = self.app
-        node = app.nm.getByUUID(uuid)
-        vote = any(x[1].isReadable() for x in app.pt.iterNodeCell(node))
         for ttid, tid in tid_dict.iteritems():
             if tid:
                 self._locked_dict[ttid] = tid
-            if vote:
             self._voted_dict[ttid].add(uuid)
 
     def answerFinalTID(self, conn, tid):