tweak: add option to simulate

Initially, I wanted to do the simulation inside neoctl but it has no knowledge
of the topology (the master don't send devpath values of storage nodes).
Therefore, the work is delegated to the master node, which implies a change
of the protocol.

neo/lib/protocol.py

@@ -1254,10 +1254,14 @@ class TweakPartitionTable(Packet):
     :nodes: ctl -> A -> M
     """
     _fmt = PStruct('tweak_partition_table',
+        PBoolean('dry_run'),
         PFUUIDList,
     )
 
-    _answer = Error
+    _answer = PStruct('answer_tweak_partition_table',
+        PBoolean('changed'),
+        PFRowList,
+    )
 
 class NotifyNodeInformation(Packet):
     """
@@ -1775,8 +1779,8 @@ class Packets(dict):
                     SetNodeState, ignore_when_closed=False)
     AddPendingNodes = register(
                     AddPendingNodes, ignore_when_closed=False)
-    TweakPartitionTable = register(
-                    TweakPartitionTable, ignore_when_closed=False)
+    TweakPartitionTable, AnswerTweakPartitionTable = register(
+                    TweakPartitionTable)
     SetNumReplicas = register(
                     SetNumReplicas, ignore_when_closed=False)
     SetClusterState = register(

neo/master/handlers/administration.py

@@ -195,17 +195,28 @@ class AdministrationHandler(MasterHandler):
         conn.answer(Errors.Ack(''))
 
     @__change_pt_rpc
-    def tweakPartitionTable(self, conn, uuid_list):
+    def tweakPartitionTable(self, conn, dry_run, uuid_list):
         app = self.app
         drop_list = [node for node in app.nm.getStorageList()
             if node.getUUID() in uuid_list or not node.isRunning()]
+        if dry_run:
+            pt = object.__new__(app.pt.__class__)
+            new_nodes = pt.load(app.pt.getID(), app.pt.getReplicas(),
+                                app.pt.getRowList(), app.nm)
+            assert not new_nodes
+            pt.addNodeList(node
+                for node, count in app.pt.count_dict.iteritems()
+                if not count)
+        else:
+            pt = app.pt
         try:
-            changed_list = app.pt.tweak(drop_list)
+            changed_list = pt.tweak(drop_list)
         except PartitionTableException, e:
             raise AnswerDenied(str(e))
-        else:
+        if not dry_run:
             app.broadcastPartitionChanges(changed_list)
-        conn.answer(Errors.Ack(''))
+        conn.answer(Packets.AnswerTweakPartitionTable(
+            bool(changed_list), pt.getRowList()))
 
     @check_state(ClusterStates.RUNNING)
     def truncate(self, conn, tid):

neo/neoctl/app.py

@@ -183,9 +183,15 @@ class TerminalNeoCTL(object):
           No change is done to the specified/down storage nodes and they don't
           count as replicas. The purpose of listing nodes is usually to drop
           them once the data is replicated to other nodes.
-          Parameters: [node [...]]
-        """
-        return self.neoctl.tweakPartitionTable(map(self.asNode, params))
+          Parameters: [-n] [node [...]]
+            -n: dry run
+        """
+        dry_run = params[0] == '-n'
+        changed, row_list = self.neoctl.tweakPartitionTable(
+            map(self.asNode, params[dry_run:]), dry_run)
+        if changed:
+            return self.formatRowList(enumerate(row_list))
+        return 'No change done.'
 
     def killNode(self, params):
         """

neo/neoctl/handler.py

@@ -63,3 +63,4 @@ class CommandEventHandler(EventHandler):
     answerLastIDs = __answer(Packets.AnswerLastIDs)
     answerLastTransaction = __answer(Packets.AnswerLastTransaction)
     answerRecovery = __answer(Packets.AnswerRecovery)
+    answerTweakPartitionTable = __answer(Packets.AnswerTweakPartitionTable)

neo/neoctl/neoctl.py

@@ -91,11 +91,11 @@ class NeoCTL(BaseApplication):
             raise RuntimeError(response)
         return response[2]
 
-    def tweakPartitionTable(self, uuid_list=()):
-        response = self.__ask(Packets.TweakPartitionTable(uuid_list))
-        if response[0] != Packets.Error or response[1] != ErrorCodes.ACK:
+    def tweakPartitionTable(self, uuid_list=(), dry_run=False):
+        response = self.__ask(Packets.TweakPartitionTable(dry_run, uuid_list))
+        if response[0] != Packets.AnswerTweakPartitionTable:
             raise RuntimeError(response)
-        return response[2]
+        return response[1:]
 
     def setNumReplicas(self, nr):
         response = self.__ask(Packets.SetNumReplicas(nr))