More bugfixes to backup mode

- catch OperationFailure
- reset transaction manager when leaving backup mode
- send appropriate target tid to a storage that updates a outdated cell
- clean up partition table when leaving BACKINGUP state unexpectedly
- make sure all readable cells of a partition have the same 'backup_tid'
  if they have the same data, so that we know when internal replication is
  finished when leaving backup mode
- fix storage not finished internal replication when leaving backup mode

TODO

@@ -23,6 +23,9 @@ RC  - Review output of pylint (CODE)
       Consider the need to implement a keep-alive system (packets sent
       automatically when there is no activity on the connection for a period
       of time).
+    - When all cells are OUT_OF_DATE in backup mode, the one with most data
+      could become UP_TO_DATE with appropriate backup_tid, so that the cluster
+      stays operational (FEATURE).
     - Finish renaming UUID into NID everywhere (CODE)
     - Consider using multicast for cluster-wide notifications. (BANDWITH)
       Currently, multi-receivers notifications are sent in unicast to each

neo/lib/protocol.py

@@ -26,7 +26,7 @@ except ImportError:
     pass
 
 # The protocol version (major, minor).
-PROTOCOL_VERSION = (13, 1)
+PROTOCOL_VERSION = (14, 1)
 
 # Size restrictions.
 MIN_PACKET_SIZE = 10
@@ -1497,12 +1497,12 @@ class ReplicationDone(Packet):
 
 class Truncate(Packet):
     """
+    XXX: Used for both make storage consistent and leave backup mode
     M -> S
     """
-    _fmt = PStruct('ask_truncate',
+    _fmt = PStruct('truncate',
         PTID('tid'),
     )
-    _answer = PFEmpty
 
 
 StaticRegistry = {}
@@ -1723,7 +1723,7 @@ class Packets(dict):
                     AddTransaction)
     AddObject = register(
                     AddObject)
-    AskTruncate, AnswerTruncate = register(
+    Truncate = register(
                     Truncate)
 
 def Errors():

neo/master/app.py

@@ -279,10 +279,6 @@ class Application(object):
         try:
             while True:
                 poll(1)
-        except OperationFailure:
-            # If not operational, send Stop Operation packets to storage
-            # nodes and client nodes. Abort connections to client nodes.
-            logging.critical('No longer operational')
         except StateChangedException, e:
             if e.args[0] != ClusterStates.STARTING_BACKUP:
                 raise
@@ -337,13 +333,20 @@ class Application(object):
             self.runManager(RecoveryManager)
             while True:
                 self.runManager(VerificationManager)
+                try:
                     if self.backup_tid:
                         if self.backup_app is None:
                             raise RuntimeError("No upstream cluster to backup"
                                                " defined in configuration")
                         self.backup_app.provideService()
-                else:
+                        # Reset connection with storages (and go through a
+                        # recovery phase) when leaving backup mode in order
+                        # to get correct last oid/tid.
+                        self.runManager(RecoveryManager)
+                        continue
                     self.provideService()
+                except OperationFailure:
+                    logging.critical('No longer operational')
                 for node in self.nm.getIdentifiedList():
                     if node.isStorage() or node.isClient():
                         node.notify(Packets.StopOperation())
@@ -463,8 +466,6 @@ class Application(object):
             while self.tm.hasPending():
                 self.em.poll(1)
         except OperationFailure:
-            # If not operational, send Stop Operation packets to storage
-            # nodes and client nodes. Abort connections to client nodes.
             logging.critical('No longer operational')
 
         logging.info("asking remaining nodes to shutdown")

neo/master/backup_app.py

@@ -21,9 +21,10 @@ from neo.lib import logging
 from neo.lib.bootstrap import BootstrapManager
 from neo.lib.connector import getConnectorHandler
 from neo.lib.exception import PrimaryFailure
+from neo.lib.handler import EventHandler
 from neo.lib.node import NodeManager
-from neo.lib.protocol import CellStates, ClusterStates, NodeTypes, Packets
-from neo.lib.protocol import uuid_str, INVALID_TID, ZERO_TID
+from neo.lib.protocol import CellStates, ClusterStates, \
+    NodeStates, NodeTypes, Packets, uuid_str, INVALID_TID, ZERO_TID
 from neo.lib.util import add64, dump
 from .app import StateChangedException
 from .pt import PartitionTable
@@ -144,26 +145,32 @@ class BackupApplication(object):
                 while pt.getCheckTid(xrange(pt.getPartitions())) < tid:
                     poll(1)
                 last_tid = app.getLastTransaction()
+                handler = EventHandler(app)
                 if tid < last_tid:
                     assert tid != ZERO_TID
                     logging.warning("Truncating at %s (last_tid was %s)",
                         dump(app.backup_tid), dump(last_tid))
-                    p = Packets.AskTruncate(tid)
-                    connection_list = []
+                # XXX: We want to go through a recovery phase in order to
+                #      initialize the transaction manager, but this is only
+                #      possible if storages already know that we left backup
+                #      mode. To that purpose, we always send a Truncate packet,
+                #      even if there's nothing to truncate.
+                p = Packets.Truncate(tid)
                 for node in app.nm.getStorageList(only_identified=True):
                     conn = node.getConnection()
-                        conn.ask(p)
-                        connection_list.append(conn)
-                    for conn in connection_list:
-                        while conn.isPending():
-                            poll(1)
-                    app.setLastTransaction(tid)
+                    conn.setHandler(handler)
+                    node.setState(NodeStates.TEMPORARILY_DOWN)
+                    # Packets will be sent at the beginning of the recovery
+                    # phase.
+                    conn.notify(p)
+                    conn.abort()
                 # If any error happened before reaching this line, we'd go back
                 # to backup mode, which is the right mode to recover.
                 del app.backup_tid
                 break
             finally:
                 del self.primary_partition_dict, self.tid_list
+                pt.clearReplicating()
 
     def nodeLost(self, node):
         getCellList = self.app.pt.getCellList
@@ -205,9 +212,25 @@ class BackupApplication(object):
                 node_list = []
                 for cell in pt.getCellList(offset, readable=True):
                     node = cell.getNode()
-                    assert node.isConnected()
-                    assert cell.backup_tid < last_max_tid or \
-                           cell.backup_tid == prev_tid
+                    assert node.isConnected(), node
+                    if cell.backup_tid == prev_tid:
+                        # Let's given 4 TID t0,t1,t2,t3: if a cell is only
+                        # modified by t0 & t3 and has all data for t0, 4 values
+                        # are possible for its 'backup_tid' until it replicates
+                        # up to t3: t0, t1, t2 or t3 - 1
+                        # Choosing the smallest one (t0) is easier to implement
+                        # but when leaving backup mode, we would always lose
+                        # data if the last full transaction does not modify
+                        # all partitions. t1 is wrong for the same reason.
+                        # So we have chosen the highest one (t3 - 1).
+                        # t2 should also work but maybe harder to implement.
+                        cell.backup_tid = add64(tid, -1)
+                        logging.debug(
+                            "partition %u: updating backup_tid of %r to %s",
+                            offset, cell, dump(cell.backup_tid))
+                    else:
+                        assert cell.backup_tid < last_max_tid, (
+                            cell.backup_tid, last_max_tid, prev_tid, tid)
                     if app.isStorageReady(node.getUUID()):
                         node_list.append(node)
                 assert node_list

neo/master/handlers/backup.py

@@ -16,7 +16,7 @@
 
 from neo.lib.exception import PrimaryFailure
 from neo.lib.handler import EventHandler
-from neo.lib.protocol import CellStates
+from neo.lib.protocol import CellStates, ZERO_TID
 
 class BackupHandler(EventHandler):
     """Handler dedicated to upstream master during BACKINGUP state"""
@@ -39,7 +39,10 @@ class BackupHandler(EventHandler):
 
     def answerLastTransaction(self, conn, tid):
         app = self.app
+        if tid != ZERO_TID:
             app.invalidatePartitions(tid, set(xrange(app.pt.getPartitions())))
+        else: # upstream DB is empty
+            assert app.app.getLastTransaction() == tid
 
     def invalidateObjects(self, conn, tid, oid_list):
         app = self.app

neo/master/handlers/identification.py

@@ -48,6 +48,8 @@ class IdentificationHandler(MasterHandler):
             handler = app.client_service_handler
             human_readable_node_type = ' client '
         elif node_type == NodeTypes.STORAGE:
+            if app.cluster_state == ClusterStates.STOPPING_BACKUP:
+                raise NotReadyError
             node_ctor = app.nm.createStorage
             manager = app._current_manager
             if manager is None:

neo/master/handlers/storage.py

@@ -58,9 +58,13 @@ class StorageServiceHandler(BaseServiceHandler):
             app.backup_tid))
 
     def askUnfinishedTransactions(self, conn):
-        tm = self.app.tm
-        pending_list = tm.registerForNotification(conn.getUUID())
-        last_tid = tm.getLastTID()
+        app = self.app
+        if app.backup_tid:
+            last_tid = app.pt.getBackupTid()
+            pending_list = ()
+        else:
+            last_tid = app.tm.getLastTID()
+            pending_list = app.tm.registerForNotification(conn.getUUID())
         p = Packets.AnswerUnfinishedTransactions(last_tid, pending_list)
         conn.answer(p)
 
@@ -99,9 +103,6 @@ class StorageServiceHandler(BaseServiceHandler):
         logging.debug("%s is up for offset %s", node, offset)
         self.app.broadcastPartitionChanges(cell_list)
 
-    def answerTruncate(self, conn):
-        pass
-
     def answerPack(self, conn, status):
         app = self.app
         if app.packing is not None:

neo/master/pt.py

@@ -311,9 +311,18 @@ class PartitionTable(neo.lib.pt.PartitionTable):
             for cell in row
             if cell.isReadable())
 
+    def clearReplicating(self):
+        for row in self.partition_list:
+            for cell in row:
+                try:
+                    del cell.replicating
+                except AttributeError:
+                    pass
+
     def setBackupTidDict(self, backup_tid_dict):
         for row in self.partition_list:
             for cell in row:
+                if cell.isReadable():
                     cell.backup_tid = backup_tid_dict.get(cell.getUUID(),
                                                           ZERO_TID)
 

neo/storage/app.py

@@ -312,6 +312,9 @@ class Application(object):
                 _poll()
         finally:
             del self.task_queue
+            # XXX: Although no handled exception should happen between
+            #      replicator.populate() and the beginning of this 'try'
+            #      clause, the replicator should be reset in a safer place.
             self.replicator = Replicator(self)
             # Abort any replication, whether we are feeding or out-of-date.
             for node in self.nm.getStorageList(only_identified=True):

neo/storage/database/manager.py

@@ -436,7 +436,7 @@ class DatabaseManager(object):
     def truncate(self, tid):
         assert tid not in (None, ZERO_TID), tid
         assert self.getBackupTID()
-        self.setBackupTID(tid)
+        self.setBackupTID(None) # XXX
         for partition in xrange(self.getNumPartitions()):
             self._deleteRange(partition, tid)
         self.commit()

neo/storage/handlers/master.py

@@ -68,10 +68,10 @@ class MasterOperationHandler(BaseMasterHandler):
             dict((p, a and (a, upstream_name))
                  for p, a in source_dict.iteritems()))
 
-    def askTruncate(self, conn, tid):
+    def truncate(self, conn, tid):
         self.app.replicator.cancel()
         self.app.dm.truncate(tid)
-        conn.answer(Packets.AnswerTruncate())
+        conn.close()
 
     def checkPartition(self, conn, *args):
         self.app.checker(*args)

neo/storage/replicator.py

@@ -354,16 +354,17 @@ class Replicator(object):
             self.getCurrentConnection().close()
 
     def stop(self):
-        d = None, None
+        # Close any open connection to an upstream storage,
+        # possibly aborting current replication.
+        node = self.current_node
+        if node is not None is node.getUUID():
+            self.cancel()
         # Cancel all replication orders from upstream cluster.
         for offset in self.replicate_dict.keys():
-            addr, name = self.source_dict.get(offset, d)
+            addr, name = self.source_dict.get(offset, (None, None))
             if name:
                 tid = self.replicate_dict.pop(offset)
                 logging.info('cancel replication of partition %u from %r'
                              ' up to %s', offset, addr, dump(tid))
-        # Close any open connection to an upstream storage,
-        # possibly aborting current replication.
-        node = self.current_node
-        if node is not None is node.getUUID():
-            self.cancel()
+        # Make UP_TO_DATE cells really UP_TO_DATE
+        self._nextPartition()

neo/tests/threaded/testReplication.py

@@ -20,6 +20,7 @@ import time
 import threading
 import transaction
 import unittest
+from collections import defaultdict
 from functools import wraps
 from neo.lib import logging
 from neo.storage.checker import CHECK_COUNT
@@ -200,6 +201,10 @@ class ReplicationTests(NEOThreadedTest):
         try:
             upstream.start()
             importZODB = upstream.importZODB(random=random)
+            # Do not start with an empty DB so that 'primary_dict' below is not
+            # empty on the first iteration.
+            importZODB(1)
+            upstream.client.setPoll(0)
             backup = NEOCluster(partitions=np, replicas=2, storage_count=4,
                                 upstream=upstream)
             try:
@@ -214,11 +219,10 @@ class ReplicationTests(NEOThreadedTest):
                         p = Patch(upstream.master.tm,
                             _on_commit=onTransactionCommitted)
                     else:
-                        primary_dict = {}
+                        primary_dict = defaultdict(list)
                         for k, v in sorted(backup.master.backup_app
                                            .primary_partition_dict.iteritems()):
-                            primary_dict.setdefault(storage_list.index(v._uuid),
-                                                    []).append(k)
+                            primary_dict[storage_list.index(v._uuid)].append(k)
                         if event % 2:
                             storage = slave(primary_dict).pop()
                         else: