From df24fbeb48d8affed19f76efd409d9f6920637f8 Mon Sep 17 00:00:00 2001 From: Rodolfo Alonso Hernandez Date: Sun, 21 Jan 2024 08:42:45 +0000 Subject: [PATCH] [OVN] Document the OVN L3 scheduler: AZs distribution This new section describes how the OVN L3 schedulers distribute the ``Chassis`` candidate list among the Available Zones, in order to provide more resilience to the L3 HA: if the active LRP binding fails, the next in the list will belong to another AZ. Related-Bug: #2030741 Change-Id: I20aaeefb33c424dc1a9c13f94f2912d0fa973166 --- doc/source/admin/ovn/l3_scheduler.rst | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/doc/source/admin/ovn/l3_scheduler.rst b/doc/source/admin/ovn/l3_scheduler.rst index 57d4847d2d7..b8b57edfb26 100644 --- a/doc/source/admin/ovn/l3_scheduler.rst +++ b/doc/source/admin/ovn/l3_scheduler.rst @@ -81,8 +81,27 @@ is changed, the ``Logical_Router_Port`` is bound to the new ``Chassis`` and could break any active sessions. +Availability Zones (AZ) distribution +------------------------------------ + +Both the ``OVNGatewayChanceScheduler`` and the +``OVNGatewayLeastLoadedScheduler`` schedulers have the Availability Zones (AZ) +in consideration. If a router has any AZ defined, the schedulers will select +only those chassis located in the AZs. If no chassis meets this condition, the +``Logical_Router_Port`` will be assigned to the "neutron-ovn-invalid-chassis". + +Once the list of candidate ``Chassis`` (depending on the scheduler selected) +is created, this list is reordered to prioritize these ``Chassis`` from +different AZs. That will spread the allocation choices to all AZs; if the +current (and highest) ``Chassis`` binding fails, the next ``Chassis`` in the +list will belong to another AZ. + +This improvement was implemented in [3]_. + + References ---------- .. [1] https://review.opendev.org/c/openstack/neutron/+/893653 .. [2] https://review.opendev.org/c/openstack/neutron/+/893654 +.. [3] https://review.opendev.org/c/openstack/neutron/+/892604