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[Oleg Bondarev <obondarev@xxxxxxxxxxxx>]

Public bug reported:

If KillMode in systemd config of a neutron l3 agent service is set to
'process' - it will not kill child processes on main service stop - this
is useful when we don't want data-plane downtime on agent stop/restart
due to keepalived exit.

However in some cases graceful cleanup on l3 agent shutdown is needed -
like with containerised control plane, when kubernetes kills l3-agent
pod, it automatically kills its children (keepalived processes) in non-
graceful way, so that keepalived does not clear VIPs. This leads to a
situation when same VIP is present on different nodes and hence to long
downtime.

The proposal is to add a new l3 agent config so that it handles stop
(SIGTERM) by deleting all routers. For HA routers it results in graceful
keepalived shutdown.

** Affects: neutron
     Importance: Medium
     Assignee: Oleg Bondarev (obondarev)
         Status: New


** Tags: l3-ha l3-ipam-dhcp

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https://bugs.launchpad.net/bugs/1851609

Title:
  Add an option for graceful l3 agent shutdown

Status in neutron:
  New

Bug description:
  If KillMode in systemd config of a neutron l3 agent service is set to
  'process' - it will not kill child processes on main service stop -
  this is useful when we don't want data-plane downtime on agent
  stop/restart due to keepalived exit.

  However in some cases graceful cleanup on l3 agent shutdown is needed
  - like with containerised control plane, when kubernetes kills
  l3-agent pod, it automatically kills its children (keepalived
  processes) in non-graceful way, so that keepalived does not clear
  VIPs. This leads to a situation when same VIP is present on different
  nodes and hence to long downtime.

  The proposal is to add a new l3 agent config so that it handles stop
  (SIGTERM) by deleting all routers. For HA routers it results in
  graceful keepalived shutdown.

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