[Bug 1731595] Re: L3 HA: multiple agents are active at the same time

[James Hebden]

Hi Corey,

Unfortunately, in the case of the cloud where we are seeing this
behaviour, the updated package which Xav installed per his previous
comment does not seem to have addressed the issue. This was neutron
10.0.4-0ubuntu1~cloud0 from Cloud Archive xenial-updates/ocata.

I did notice that the packages being released for other Ubuntu releases
appear to be a newer version, 2:11.0.2-0ubuntu1.1 - is this intended?

As an update, the workaround in place for this particular issue has been
to disable L3HA on individual routers as we detect this issue. We have
this particular cloud down to a number of routers where things seem
relatively stable, now that we are closer to the 400 L3HA router mark.

Let me know if you need further information or testing performed.

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https://bugs.launchpad.net/bugs/1731595

Title:
  L3 HA: multiple agents are active at the same time

Status in Ubuntu Cloud Archive:
  Fix Released
Status in Ubuntu Cloud Archive mitaka series:
  Fix Committed
Status in Ubuntu Cloud Archive newton series:
  Fix Committed
Status in Ubuntu Cloud Archive ocata series:
  Fix Committed
Status in Ubuntu Cloud Archive pike series:
  Fix Released
Status in Ubuntu Cloud Archive queens series:
  Fix Released
Status in neutron:
  Fix Released
Status in neutron package in Ubuntu:
  Fix Released
Status in neutron source package in Xenial:
  Fix Committed
Status in neutron source package in Zesty:
  Fix Committed
Status in neutron source package in Artful:
  Fix Released
Status in neutron source package in Bionic:
  Fix Released

Bug description:
  OS: Xenial, Ocata from Ubuntu Cloud Archive
  We have three neutron-gateway hosts, with L3 HA enabled and a min of 2, max of 3.  There are approx. 400 routers defined.

  At some point (we weren't monitoring exactly) a number of the routers
  changed from being one active, and 1+ others standby, to >1 active.
  This included each of the 'active' namespaces having the same IP
  addresses allocated, and therefore traffic problems reaching
  instances.

  Removing the routers from all but one agent, and re-adding, resolved
  the issue.  Restarting one l3 agent also appeared to resolve the
  issue, but very slowly, to the point where we needed the system alive
  again faster and reverted to removing/re-adding.

  At the same time, a number of routers were listed without any agents
  active at all.  This situation appears to have been resolved by adding
  routers to agents, after several minutes downtime.

  I'm finding it very difficult to find relevant keepalived messages to
  indicate what's going on, but what I do notice is that all the agents
  have equal priority and are configured as 'backup'.

  I am trying to figure out a way to get a reproducer of this, it might
  be that we need to have a large number of routers configured on a
  small number of gateways.

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