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Message #79250
[Bug 1832028] Re: revert resize: vif-plugged external event sent too soon if Neutron is using OVS hybrid plug
Reviewed: https://review.opendev.org/667177
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=7a7a223602ca5aa0aca8f65a6ab143f1d8f8ec1b
Submitter: Zuul
Branch: master
commit 7a7a223602ca5aa0aca8f65a6ab143f1d8f8ec1b
Author: Artom Lifshitz <alifshit@xxxxxxxxxx>
Date: Wed Mar 20 10:38:12 2019 -0400
Revert resize: wait for events according to hybrid plug
Since 4817165fc5938a553fafa1a69c6086f9ebe311af, when reverting a
resized instance back to the source host, the libvirt driver waits for
vif-plugged events when spawning the instance. When called from
finish_revert_resize() in the source compute manager, libvirt's
finish_revert_migration() does not pass vifs_already_plugged to
_create_domain_and_network(), making the latter use the default False
value.
When the source compute manager calls
network_api.migrate_instance_finish() in finish_revert_resize(), this
updates the port binding back to the source host. If Neutron is
configured to use OVS hybrid plug, it will send the vif-plugged event
immediately after completing this request. This happens before the
virt driver's finish_revert_migration() method is called. This causes
the wait in the libvirt driver to time out because the event is
received before Nova starts waiting for it.
The neutron ovs l2 agent sends vif-plugged events when two conditions
are met. First the port must be bound to the host managed by the
l2 agent and second, the agent must have completed configuring the
port on ovs. This involves assigning the port a local VLAN for tenant
isolation, applying security group rules if required and applying
QoS policies or other agent extensions like service function chaining.
During the boot process, we bind the port first to the host
then plug the interface into ovs which triggers the l2 agent to
configure it resulting in the emission of the vif-plugged event.
In the revert case, as noted above, since the vif is already plugged
on the source node when hybrid-plug is used, binding the port to the
source node fulfils the second condition to send the vif-plugged event.
Events sent immediately after port binding update are hereafter known
as "bind-time" events. For ports that do not use OVS hybrid plug,
Neutron will continue to send vif-plugged events only when Nova
actually plugs the VIF. These types of events are hereafter known as
"plug-time" events. OVS hybrid plug is a per agent setting, so for
a particular host, bind-time events are an all-or-nothing thing for the
ovs backend: either all VIF_TYPE=ovs ports have them, or no ovs ports
have them. In general, a host will only have one network backend.
The only exception to this is SR-IOV. SR-IOV is commonly deployed on
the same host as other network backends such as OVS or linuxbridge.
SR-IOV ports with VNIC_TYPE=direct-physical will always have only
bind-time events. If an instance mixes OVS ports with hybrid-plug=False
with direct physical ports, it will have both kinds of events.
For same host resize reverts we do not update the binding host as the
host does not change, as such for same host resize we do not receive
bind time events. For same host revert we therefore do not wait for
bind time events in the compute manager.
This patch adds functions to the NetworkInfo model that return what
kinds of events each VIF has. These are then used in the migration
revert logic to decide when to wait for external events: in the
compute manager, when binding the port, for bind-time events,
and/or in libvirt, when plugging the VIFs, for plug-time events.
Closes-bug: #1832028
Closes-Bug: #1833902
Co-Authored-By: Sean Mooney <work@xxxxxxxxxxxxxxx>
Change-Id: I51673e58fc8d5f051df911630f6d7a928d123a5b
** Changed in: nova
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/1832028
Title:
revert resize: vif-plugged external event sent too soon if Neutron is
using OVS hybrid plug
Status in OpenStack Compute (nova):
Fix Released
Status in OpenStack Compute (nova) rocky series:
In Progress
Status in OpenStack Compute (nova) stein series:
In Progress
Bug description:
Description
===========
This is all only when Neutron is using OVS with hybrid plugging.
When reverting a resized instance back to its original source host,
Nova will timeout waiting for the vif-plugged external event, and
never finish the revert. This happens because the event is sent by
Neutron as soon as Nova updates the port binding to point back to the
original source. This happens before the virt driver gets ready to
listen for external events, so the event arrives, just too soon, and
Nova times out.
Steps to reproduce
==================
1. Resize an instance
2. When it's in VERIFY_RESIZE, revert it
Expected result
===============
Instance reverts correctly.
Actual result
=============
Instance goes to ERROR.
Environment
===========
OVS with hybrid plug. Reported in OSP14/Rocky [1], reproduced on
master [2] [3].
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1678681
[2] https://review.opendev.org/#/c/660782/
[3] https://review.opendev.org/#/c/653498/
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References