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[Armando Migliaccio <1581220@xxxxxxxxxxxxxxxxxx>]

As Kevin pointed out and as I also can see from code [1] (both for
methods _add_auto_ip and _add_ip_from_pool) the action of associating a
floating ip to server is a two step process that involve creating an
unassociated FIP which then gets assigned to a fixed ip via its port
uuid (neutron case). It seems that the race part is where two separate
threads get hold of the same FIP uuid: that can happen into cases (as
far as I can see): a) pull a FIP from a list of available ones; b)
create a fresh one.

I wonder if the source of contention is in the a) code path, and whether
there's a chance to protect this critical region on client-side. Two
separate client requests should lead to two separate FIPs being
generated and thus lead to separate associations and thus no contention.

[1] https://github.com/openstack-infra/shade/blob/d026cab5c7548517aa15e969fdd336b9fc663e7d/shade/openstackcloud.py#L3955
[2] https://github.com/openstack-infra/shade/blob/d026cab5c7548517aa15e969fdd336b9fc663e7d/shade/openstackcloud.py#L3296
[3] https://github.com/openstack-infra/shade/blob/d026cab5c7548517aa15e969fdd336b9fc663e7d/shade/openstackcloud.py#L3304

** No longer affects: nova

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https://bugs.launchpad.net/bugs/1581220

Title:
  race leads same floating ip to be associated to separate ports

Status in neutron:
  Incomplete

Bug description:
  It looks like steps to create server as outlined in [2] lead to the
  same FIP being associated to two individual ports [1] (offending fip
  f1169479-7d88-4526-a60a-82f18b617077). It looks like two interleaving
  calls to do FIP association by port-id will end up clashing. This has
  been reproduced in Kilo, but we would need to find out if the race is
  still possible in newer versions.

  [1] https://gist.github.com/cloudnull/d90eff7efc524844d8d3504fea8fa419
  [2] https://gist.github.com/cloudnull/2f3931e51062dc7b325faf9a24974006

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