Comment 7 for bug 1761536

The crashdump shows multiple occurrences of RPC Timeouts in neutron-openvswitch-agent.log:
Timeout in RPC method tunnel_sync. Waiting for 54 seconds before next attempt. If the server is not down, consider increasing the rpc_response_timeout option as Neutron server(s) may be overloaded and unable to respond quickly enough.: MessagingTimeout: Timed out waiting for a reply to message ID 6ecd4578ba6942769d00f39be63017a7

Right before the server build failure this message is logged:
2018-04-05 11:19:04.188 232295 ERROR neutron.agent.linux.openvswitch_firewall.firewall [req-8b07034a-1536-4fb0-a356-5df4be8a2c8c - - - - -] Initializing unfiltered port e84c9f3c-d412-45de-80fc-acf2af4ab56b that does not exist in ovsdb: Port e84c9f3c-d412-45de-80fc-acf2af4ab56b is not managed by this agent..: OVSFWPortNotFound: Port e84c9f3c-d412-45de-80fc-acf2af4ab56b is not managed by this agent.

It seems to me that the Neutron OpenvSwitch Agent on compute node nova-compute-kvm_4 is out of sync and that the worker-multiplier and/or rpc-response-timeout config options of the deployment need adjusting.