[Bug 1964348] Re: [20.03][20.12] ovn-controller should update OF rules atomically

[Frode Nordahl]

** Changed in: cloud-archive
       Status: New => Fix Released

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https://bugs.launchpad.net/bugs/1964348

Title:
  [20.03][20.12] ovn-controller should update OF rules atomically

Status in Ubuntu Cloud Archive:
  Fix Released
Status in Ubuntu Cloud Archive wallaby series:
  New
Status in ovn package in Ubuntu:
  Fix Released
Status in ovn source package in Focal:
  New

Bug description:
  Originally reported at [0] and fixed in OVN 21.06 by [1].

  If some OF rules needs to be replaced due to logical flow changes,
  ovn-controller deletes old rules first and adds new ones later.
  In a complex scenario with big number of flows a lot of time
  can pass between these events leading to the dataplane downtime
  and packet loss.  Also, while these changes are in progress,
  OVS will use incomplete pipelines that will also lead to packet
  drops.

  To avoid this, all flow modifications should be done atomically,
  so there will be always some version of OF rules installed that
  can handle dataplane traffic and it will be complete in terms of
  reflecting some consistent set of logical flows.  Wrapping all
  flow modifications into atomic ordered bundle to achieve that.

  0: https://bugzilla.redhat.com/1947398
  1: https://github.com/ovn-org/ovn/commit/7687d878f1e30c98d52b37bade42293f2a1e9bd3

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