[neutron] Flow drop on agent restart with openvswitch firewall driver

Alexis Deberg alexis.deberg at ubisoft.com
Tue Sep 8 14:46:29 UTC 2020


Hi All,

I'm looking for ideas as we need to upgrade our Neutron deployment and it looks like it would impact workloads a bit much for now to do so and i'm no master of the neutron code...

We're running Neutron 14.0.2 with ml2 plugin and firewall_driver set as openvswitch. drop_flows_on_start is default False.

Reading at some old bug reports my understanding was that a restart of the neutron-openvswitch-agent should not impact existing flows and be seamless, but this is not what I'm experiencing as I see some temporary drop(s) around when ovs-fctl del-flows/add-flows is called on br-int (either east-west traffic or north-south). I tried switching to iptables_hybrid driver instead and I don't see the issue in that case.

e.g when a wget download is happening on an instance while the agent is restarting, I see the following: 2020-09-08 14:26:09 (12.2 MB/s) - Read error at byte 146971864/7416743936 (Success). Retrying

I'm a bit lot so i'm wondering if that's expected/known behavior, if a workaround is possible....

Let me know if a bug report might be a better place to dig deeper or not or if you want additional information... or if I missed a closed bug.

Thanks !
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