After a large number of Virtual NWs were created, the RaftState of one cluster node became abnormal.
It changed from Leader to IsolatedLeader, Follower to Candidate.
Then RaftState not changed even after 16 hours.
And the RaftState of other 2 nodes did not changed at all.

Environment Details:
OpenStack Version: stable/ocata
ODL Version: carbon-FR + L2GW related patches
ODLのMAX heap: JAVA_MAX_MEM="6144m"

Reproduction steps:
1. Initialization and set up of Controller/Compute/L2GW Node
2. Creation of 1000 virtual NWs
3. Creation of 1 L2GW GATEWAY
4. Creation of 1000 L2GW CONNECTIONs

• This phenomenon does not always occur (occurrence ratio: 1/3)

Karaf logs:

• Split Karaf logs are attached.
  The time when RaftState became abnormal is around 17: 20-17: 23.

odl1#
karaf.log.3:2017-08-08 13:28:41,123 | INFO | lt-dispatcher-22 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier:akka.tcp://opendaylight-cluster-data@192.168.101.8:2550/user/shardmanager-operational/member-1-shard-topology-operational/member-1-shard-topology-operational-notifier#1974074480 created and ready for shard:member-1-shard-topology-operational
karaf.log.3:2017-08-08 13:28:41,131 | INFO | lt-dispatcher-23 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-1-shard-topology-operational , received role change from null to Follower
karaf.log.3:2017-08-08 13:28:41,132 | INFO | lt-dispatcher-23 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-1-shard-topology-operational , registered listener akka://opendaylight-cluster-data/user/shardmanager-operational
karaf.log.3:2017-08-08 13:28:51,162 | INFO | lt-dispatcher-36 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-1-shard-topology-operational , received role change from Follower to Candidate
karaf.log.3:2017-08-08 13:28:51,165 | INFO | lt-dispatcher-41 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-1-shard-topology-operational , received role change from Candidate to Leader
karaf.log:2017-08-08 17:20:35,381 | INFO | lt-dispatcher-45 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-1-shard-topology-operational , received role change from Leader to IsolatedLeader

odl2#
karaf.log.1:2017-08-08 13:28:41,124 | INFO | lt-dispatcher-23 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier:akka.tcp://opendaylight-cluster-data@192.168.101.13:2550/user/shardmanager-operational/member-2-shard-topology-operational/member-2-shard-topology-operational-notifier#-1501266548 created and ready for shard:member-2-shard-topology-operational
karaf.log.1:2017-08-08 13:28:41,130 | INFO | ult-dispatcher-3 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-2-shard-topology-operational , received role change from null to Follower
karaf.log.1:2017-08-08 13:28:41,138 | INFO | ult-dispatcher-3 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-2-shard-topology-operational , registered listener akka://opendaylight-cluster-data/user/shardmanager-operational
karaf.log:Caused by: akka.pattern.AskTimeoutException: Ask timed out on [ActorSelection[Anchor(akka.tcp://opendaylight-cluster-data@192.168.101.8:2550/), Path(/user/shardmanager-operational/member-1-shard-topology-operational/shard-topology-member-2:datastore-operational@0:89656_200508#2123488974)]] after [5000 ms]. Sender[null] sent message of type "org.opendaylight.controller.cluster.datastore.messages.ReadData".
karaf.log:ReadFailedException{message=Error checking ReadData for path /(urn:TBD:params:xml:ns:yang:network-topology?revision=2013-10-21)network-topology/topology/topology[

{(urn:TBD:params:xml:ns:yang:network-topology?revision=2013-10-21)topology-id=hwvtep:1}

]/node/node[

{(urn:TBD:params:xml:ns:yang:network-topology?revision=2013-10-21)node-id=hwvtep://uuid/44307ca2-4ebf-4470-8d06-7e377959a41c}

]/AugmentationIdentifier

{childNames=[(urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)remote-ucast-macs, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)managers, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)local-mcast-macs, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)switches, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)logical-routers, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)remote-arp-sources, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)local-ucast-macs, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)logical-binding-stats, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)connection-info, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)acls, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)local-arp-sources, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)remote-mcast-macs, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)logical-switches]}

/(urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)logical-switches/logical-switches[

{(urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)hwvtep-node-name=a40b416f-18c8-43a8-9466-7759d62e4ce4}

], errorList=[RpcError [message=Error checking ReadData for path /(urn:TBD:params:xml:ns:yang:network-topology?revision=2013-10-21)network-topology/topology/topology[

{(urn:TBD:params:xml:ns:yang:network-topology?revision=2013-10-21)topology-id=hwvtep:1}

]/node/node[

{(urn:TBD:params:xml:ns:yang:network-topology?revision=2013-10-21)node-id=hwvtep://uuid/44307ca2-4ebf-4470-8d06-7e377959a41c}

]/AugmentationIdentifier

{childNames=[(urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)remote-ucast-macs, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)managers, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)local-mcast-macs, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)switches, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)logical-routers, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)remote-arp-sources, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)local-ucast-macs, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)logical-binding-stats, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)connection-info, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)acls, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)local-arp-sources, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)remote-mcast-macs, (urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)logical-switches]}

/(urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)logical-switches/logical-switches[

{(urn:opendaylight:params:xml:ns:yang:ovsdb:hwvtep?revision=2015-09-01)hwvtep-node-name=a40b416f-18c8-43a8-9466-7759d62e4ce4}

], severity=ERROR, errorType=APPLICATION, tag=operation-failed, applicationTag=null, info=null, cause=akka.pattern.AskTimeoutException: Ask timed out on [ActorSelection[Anchor(akka.tcp://opendaylight-cluster-data@192.168.101.8:2550/), Path(/user/shardmanager-operational/member-1-shard-topology-operational/shard-topology-member-2:datastore-operational@0:89656_200508#2123488974)]] after [5000 ms]. Sender[null] sent message of type "org.opendaylight.controller.cluster.datastore.messages.ReadData".]]}

odl3#
2017-08-08 13:28:41,130 | INFO | lt-dispatcher-20 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier:akka.tcp://opendaylight-cluster-data@192.168.101.15:2550/user/shardmanager-operational/member-3-shard-topology-operational/member-3-shard-topology-operational-notifier#1779121060 created and ready for shard:member-3-shard-topology-operational
2017-08-08 13:28:41,142 | INFO | lt-dispatcher-22 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-3-shard-topology-operational , received role change from null to Follower
2017-08-08 13:28:41,142 | INFO | lt-dispatcher-48 | RoleChangeNotifier | 204 - org.opendaylight.controller.sal-clustering-commons - 1.5.0.Carbon | RoleChangeNotifier for member-3-shard-topology-operational , registered listener akka://opendaylight-cluster-data/user/shardmanager-operational