The following exception occurs when create l2gw connection in L2GW HA environment.
OVSDB transaction of l2gw connection creation is not executed to the end.

• Exception:
  2017-11-09 10:34:06,892 | ERROR | n-invoker-impl-0 | vtepOperationalCommandAggregator | 355 - org.opendaylight.ovsdb.hwvtepsouthbound-impl - 1.5.0 | Execution of command org.opendaylight.ovsdb.hwvtepsouthbound.transactions.md.HwvtepLogicalSwitchUpdateCommand@47222317 failed with the following exception. Continuing the execution of remaining commands
  java.util.NoSuchElementException
  at java.util.HashMap$HashIterator.nextNode(HashMap.java:1439)[:1.8.0_144]
  at java.util.HashMap$KeyIterator.next(HashMap.java:1461)[:1.8.0_144]
  at org.opendaylight.ovsdb.hwvtepsouthbound.transactions.md.HwvtepLogicalSwitchUpdateCommand.buildConnectionNode(HwvtepLogicalSwitchUpdateCommand.java:91)[355:org.opendaylight.ovsdb.hwvtepsouthbound-impl:1.5.0]
  at org.opendaylight.ovsdb.hwvtepsouthbound.transactions.md.HwvtepLogicalSwitchUpdateCommand.updateLogicalSwitch(HwvtepLogicalSwitchUpdateCommand.java:63)[355:org.opendaylight.ovsdb.hwvtepsouthbound-impl:1.5.0]
  at org.opendaylight.ovsdb.hwvtepsouthbound.transactions.md.HwvtepLogicalSwitchUpdateCommand.execute(HwvtepLogicalSwitchUpdateCommand.java:55)[355:org.opendaylight.ovsdb.hwvtepsouthbound-impl:1.5.0]
  at org.opendaylight.ovsdb.hwvtepsouthbound.transactions.md.HwvtepOperationalCommandAggregator.execute(HwvtepOperationalCommandAggregator.java:59)[355:org.opendaylight.ovsdb.hwvtepsouthbound-impl:1.5.0]
  at org.opendaylight.ovsdb.hwvtepsouthbound.transactions.md.TransactionInvokerImpl.run(TransactionInvokerImpl.java:107)[355:org.opendaylight.ovsdb.hwvtepsouthbound-impl:1.5.0]
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)[:1.8.0_144]
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)[:1.8.0_144]
  at java.lang.Thread.run(Thread.java:748)[:1.8.0_144]

○Cause

"replication-mode" is not set in HWVTEP logical-switches entry in DS
The place where it expect to be set is marked with "＊" below:

config/network-topology:network-topology
{
"network-topology": {
"topology": [
{
"topology-id": "hwvtep:1",
"node": [
{
"node-id": "hwvtep://uuid/8ec2ca5b-7038-4102-ae8a-e17e9a39311a",
:
"hwvtep:logical-switches": [
{
"hwvtep-node-name": "2a0f4784-3c02-4861-a7bc-0b3a84eaddf7",
"tunnel-key": "2061",
"logical-switch-uuid": "64f8b1e6-ca65-3acf-9541-5158a619fd08",
＊ "replication-mode": "source_node"
}
],
:
},
}
:
}
]
}
}

○Reproduction steps:

• 1. Initialize and Configure ControllerNode/ComputeNode/ODL
• 2. Create NW/Router/VM
• 3. Configure L2GW HA Cluster
• 4. Create L2GW GATEWAY
• 5. Create L2GW CONNECTION