neutron ovs agent restart introduces downtime

[Dmitry Sutyagin]

Reproducible on - all version up to 8.0, have not tried on 9.0

Description:
  restarting neutron-plugin-openvswitch-agent introduces network downtime
  stop of the agent does not introduce downtime, but start does.

Steps to reproduce:
  1 - start ping of a floating ip / internal ip of a VM
  2 - stop neutron-plugin-openvswitch-agent on compute
  3 - start neutron-plugin-openvswitch-agent on compute
  4 - observe several lost packets

I believe it should be possible to start agent without manipulating ovs internals if they are already correctly set up - we need to make necessary checks (read operations) and act based on results, and avoid touching anything which is already configured correctly.

I believe a similar issue is with neutron-l3-agent if we kill it and then it starts back up (by pacemaker)

[Bug Checker Bot (bug-checker)]

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[Eugene Nikanorov (enikanorov)]

losing several packets is not yet a downtime.
tcp layer can handle that.

There was a fix upstream which eliminates rebuilding the connection between br-int and physical bridges.

[Dina Belova (dbelova)]

Targeting to 10.0 (at least for now) due to medium priority.

[Alexander Ignatov (aignatov)]

@Dmitry, I was tried to reproduce this issue on released 9.0 ISO, it's not reproducible there with the same scenario you mentioned in bug description. I believe this is fixed by https://review.openstack.org/#/q/I05bf5105a6f3acf6a313ce6799648a095cf8ec96,n,z

You can try latest 8.0-MU to check if it's fixed in liberty-based code.
Closing this bug for 9.1 and 10.0.

[Dmitry Sutyagin (dsutyagin)]

@Alexander,

This is reproducible on the latest 8.0 MU. Will test on 9.0 today to confirm your results.

[Dmitry Sutyagin (dsutyagin)]

Confirm - not reproducible in 9.0, and like I stated earlier - reproducible in 8.0 MU1. However maybe 8.0 MU2 due to be released next week will fix that issue, I don't know.

[Denis Meltsaykin (dmeltsaykin)]

Closing as Won't Fix as this is a medium importance non-customer-found bug.