[Bug 2017748] Re: [SRU] OVN: ovnmeta namespaces missing during scalability test causing DHCP issues

[OpenStack Infra]

Fix proposed to branch: unmaintained/zed
Review: https://review.opendev.org/c/openstack/neutron/+/926666

** Changed in: cloud-archive/yoga
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/2017748

Title:
  [SRU] OVN:  ovnmeta namespaces missing during scalability test causing
  DHCP issues

Status in Ubuntu Cloud Archive:
  New
Status in Ubuntu Cloud Archive yoga series:
  In Progress
Status in neutron:
  New
Status in neutron ussuri series:
  Fix Released
Status in neutron victoria series:
  New
Status in neutron wallaby series:
  New
Status in neutron xena series:
  New
Status in neutron package in Ubuntu:
  Fix Released
Status in neutron source package in Focal:
  New
Status in neutron source package in Jammy:
  New

Bug description:
  [Impact]

  ovnmeta- namespaces are missing intermittently then can't reach to VMs

  [Test Case]
  TBD
  - Not able to reproduce this easily.

  [Where problems could occur]
  This patches are related to ovn metadata agent in compute. 
  VM's connectivity can possibly be affected by this patch when ovn is used. 
  Biding port to datapath could be affected.

  [Others]

  == ORIGINAL DESCRIPTION ==

  Reported at: https://bugzilla.redhat.com/show_bug.cgi?id=2187650

  During a scalability test it was noted that a few VMs where having
  issues being pinged (2 out of ~5000 VMs in the test conducted). After
  some investigation it was found that the VMs in question did not
  receive a DHCP lease:

  udhcpc: no lease, failing
  FAIL
  checking http://169.254.169.254/2009-04-04/instance-id
  failed 1/20: up 181.90. request failed

  And the ovnmeta- namespaces for the networks that the VMs was booting
  from were missing. Looking into the ovn-metadata-agent.log:

  2023-04-18 06:56:09.864 353474 DEBUG neutron.agent.ovn.metadata.agent
  [-] There is no metadata port for network
  9029c393-5c40-4bf2-beec-27413417eafa or it has no MAC or IP addresses
  configured, tearing the namespace down if needed _get_provision_params
  /usr/lib/python3.9/site-
  packages/neutron/agent/ovn/metadata/agent.py:495

  Apparently, when the system is under stress (scalability tests) there
  are some edge cases where the metadata port information has not yet
  being propagated by OVN to the Southbound database and when the
  PortBindingChassisEvent event is being handled and try to find either
  the metadata port of the IP information on it (which is updated by
  ML2/OVN during subnet creation) it can not be found and fails silently
  with the error shown above.

  Note that, running the same tests but with less concurrency did not
  trigger this issue. So only happens when the system is overloaded.

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