When starting neutron-dhcp-agent, it loops over network state synching and timesout at various locations

Issue

• neutron-dhcp-agent services are flapping in neutron agent-list and the following logs are seen in /var/log/neutron/dhcp-agent.log:

2019-11-20 07:01:16.943 463987 INFO neutron.agent.dhcp.agent [req-5b93abe5-92ee-478e-9fc0-57f4518e5660 - - - - -] Synchronizing state
2019-11-20 07:01:28.380 463987 INFO neutron.agent.dhcp.agent [req-2e20c066-928b-43a9-8d72-e426d0aca994 - - - - -] Synchronizing state complete
2019-11-20 10:27:20.094 463987 INFO neutron.agent.dhcp.agent [req-acbba601-c1e1-442e-9658-2a0770b79157 - - - - -] Agent has just been revived. Scheduling full sync
2019-11-20 13:40:27.182 30900 INFO neutron.agent.dhcp.agent [-] Synchronizing state
2019-11-20 13:40:27.241 30900 INFO neutron.agent.dhcp.agent [req-c205ad86-5ebd-42cd-8a78-f111022967e2 - - - - -] Agent has just been revived. Scheduling full sync
2019-11-20 13:46:53.401 30900 INFO neutron.agent.dhcp.agent [req-c205ad86-5ebd-42cd-8a78-f111022967e2 - - - - -] Synchronizing state
2019-11-20 13:48:33.622 80689 INFO neutron.agent.dhcp.agent [-] Synchronizing state
2019-11-20 13:48:33.731 80689 INFO neutron.agent.dhcp.agent [req-dac68e42-dfb4-48d7-8e0a-7f46d14294de - - - - -] Agent has just been revived. Scheduling full sync
2019-11-20 14:09:18.170 80689 INFO neutron.agent.dhcp.agent [req-6a1643e7-3a5f-4e57-a130-b0d00c7dea28 - - - - -] Synchronizing state complete
2019-11-20 14:09:18.199 80689 INFO neutron.agent.dhcp.agent [req-dac68e42-dfb4-48d7-8e0a-7f46d14294de - - - - -] Synchronizing state
2019-11-20 14:30:20.230 80689 INFO neutron.agent.dhcp.agent [req-7c13ec5e-2c45-4994-9412-6ec514b41f53 - - - - -] Synchronizing state complete
2019-11-20 14:30:37.439 80689 INFO neutron.agent.dhcp.agent [req-8a3258f2-ba26-4997-958b-c8b8c32b9ce2 - - - - -] Agent has just been revived. Scheduling full sync

• There is more than 500 networks and more than 5500 ports managed in this neutron environment.