[Bug 1749425] Re: Neutron integrated with OpenVSwitch drops packets and fails to plug/unplug interfaces from OVS on router interfaces at scale

James Page james.page at ubuntu.com
Wed Feb 14 17:13:30 UTC 2018


yes switching between ha/non-ha is support so long as the router is in
admin state false at the time of change (which I believe is the case in
this issue).

Some further observations; switching a router from ha mode to non-ha
mode should remove all existing router agent hosting arrangements and
then re-schedule the new non-ha router on an appropriate agent.

In the cloud experiencing this issue, I see only one remaining qrouter
namespace but its also still got a keepalived and state monitor running
- which I don't think is right.

I'm wondering whether due to the sheer number of routers being hosted on
each network node, the router never gets removed before being
rescheduled back to the same node, resulting in the teardown being
skipped in someway.

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  Neutron integrated with OpenVSwitch drops packets and fails to
  plug/unplug interfaces from OVS on router interfaces at scale

Status in neutron:
Status in openvswitch package in Ubuntu:

Bug description:
  Description:    Ubuntu 16.04.3 LTS
  Release:        16.04
  Linux 4.4.0-96-generic on AMD64
  Neutron 2:10.0.4-0ubuntu2~cloud0 from Cloud Archive xenial-updates/ocata
  OpenVSwitch 2.6.1-0ubuntu5.2~cloud0 from Cloud Archive xenial-upates/ocata

  In an environment with three bare-metal Neutron deployments, hosting
  upward of 300 routers, with approximately the same number of
  instances, typically one router per instance, packet loss on instances
  accessed via floating IPs, including complete connectivity loss, is
  experienced. The problem is exacerbated by enabling L3HA, likely due
  to the increase in router namespaces to be scheduled and managed, and
  the additional scheduling work of bringing up keepalived and
  monitoring the keepalived VIP.

  Reducing the number of routers and rescheduling routers on new hosts,
  causing the routers to undergo a full recreation of namespace,
  iptables rules, and replugging of interfaces into OVS will correct
  packet loss or connectivity loss on impacted routers.

  On Neutron hosts in this environment, we have used systemtap to trace
  calls to kfree_skb which reveals the majority of dropped packets occur
  in the openvswitch module, notably on the br-int bridge. Inspecting
  the state of OVS shows many qtap interfaces which are no longer
  present on the Neutron host which are still plugged in to OVS.

  Diagnostic outputs in following comments.

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