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[Ann Kamyshnikova <akamyshnikova@xxxxxxxxxxxx>]

** Changed in: neutron
       Status: In Progress => Opinion

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https://bugs.launchpad.net/bugs/1566194

Title:
  Make sure resources for HA router exists before the router creation

Status in neutron:
  Opinion

Bug description:
  Before HA rouer is used by agent,
  1) HA network should be created
  2) vr_id has to be allocated
  3) HA router should able to create sufficient number of ports on HA network

  If scheduler(from rpc worker) process the HA router(as router is available in DB) before these resources are created, then the following races(between api and rpc workers) can happen
  1) Race for creating HA network
  2) vr_id not avialable for agent, so can't spawn HA proxy process
  3) If creating router ports in api worker is failed, router is deleted. So rpc worker will have races as router is deleted while it is binding router's ha ports to agent.

  To avoid this, l3 scheduler should skip this router(while syncing for
  the agent) if above resources are not yet created.

  To facilitate this, new status("ALLOCATING") is proposed for HA router in https://review.openstack.org/#/c/257059/
  In this patch, first router is created and set status as ALLOCATING. And once all the above resources are created, its status is changed back to ACTIVE. Added proper checks(in the code) to skip using Router if it's status is ALLOCATING.

  So with this patch
  1) we are creating a new router status
  2) carefully identify where router can be accessed before its resources are created.
  3) How code behaves(during its acess to router) when status transitioned from ALLOCATING to ACTIVE
  4) API impact

  Alternatively, if we are able to create HA router's resources before
  HA router creation, we can avoid a new status and new checks, but same
  functionality as https://review.openstack.org/#/c/257059/.

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