Open Stack

Hi all,

I was checking the mail list history and this thread
https://mail.openvswitch.org/pipermail/ovs-discuss/2018-March/046438.html
caught
my attention about raft ovsdb clustering.
In my setup (OVN 20.03 and Openstack Ussuri) on the ovn-controller we have
configured
the ovn-remote="tcp:10.2X.4X.4:6642,tcp:10.2X.4X.68:6642,tcp:10.2X.4X.132:6642"
with the 3 OVN central member that they are in cluster mode.
Also on the neutron ML2 side:
[ovn]
ovn_native_dhcp = True
ovn_nb_connection =
tcp:10.2X.4X.4:6641,tcp:10.2X.4X.68:6641,tcp:10.2X.4X.132:6641
ovn_sb_connection =
tcp:10.2X.4X.4:6642,tcp:10.2X.4X.68:6642,tcp:10.2X.4X.132:6642

We are experiencing an issue with Neutron when the OVN leader decide to
take a snapshot and by design another member became leader(more less every
8 minutes):
2022-05-05T16:57:42.135Z|17401|raft|INFO|Transferring leadership to write a
snapshot.

ovs-appctl -t /var/run/ovn/ovnsb_db.ctl cluster/status OVN_Southbound
4a03
Name: OVN_Southbound
Cluster ID: ca74 (ca744caf-40cd-4751-a2f2-86e35ad6541c)
Server ID: 4a03 (4a0328dc-e9a4-495e-a4f1-0a0340fc6d19)
Address: tcp:10.2X.4X.132:6644
Status: cluster member
Role: leader
Term: 1912
Leader: self
Vote: self

Election timer: 10000
Log: [497643, 498261]
Entries not yet committed: 0
Entries not yet applied: 0
Connections: ->3d6c ->4ef0 <-3d6c <-4ef0
Servers:
    4a03 (4a03 at tcp:10.2X.4X.132:6644) (self) next_index=497874
match_index=498260
    3d6c (3d6c at tcp:10.2X.4X.68:6644) next_index=498261 match_index=498260
    4ef0 (4ef0 at tcp:10.2X.4X.4:6644) next_index=498261 match_index=498260

As I understood the tcp connections from the Neutron (NB) and
ovn-controllers (SB) to OVN Central are established only with the leader:

#OVN central leader
$ netstat -nap | grep 6642| more

tcp        0      0 0.0.0.0:6642            0.0.0.0:*               LISTEN
     -
tcp        0      0 10.2X.4X.132:6642       10.24.40.17:47278
ESTABLISHED -
tcp        0      0 10.2X.4X.132:6642       10.24.40.76:36240
ESTABLISHED -
tcp        0      0 10.2X.4X.132:6642       10.2X.4X.17:47280
ESTABLISHED -
tcp        0      0 10.2X.4X.132:6642       10.2X.4X.6:43102
 ESTABLISHED -
tcp        0      0 10.2X.4X.132:6642       10.2X.4X.75:58890
ESTABLISHED -
tcp        0      0 10.2X.4X.132:6642       10.2X.4X.6:43108
 ESTABLISHED -
tcp        0      0 10.2X.4X.132:6642       10.2X.4X.17:47142
ESTABLISHED -
tcp        0      0 10.2X.4X.132:6642       10.2X.4X.71:48808
ESTABLISHED -
tcp        0      0 10.2X.4X.132:6642       10.2X.4X.17:47096
ESTABLISHED -
#OVN follower 2

$ netstat -nap | grep 6642

tcp        0      0 0.0.0.0:6642            0.0.0.0:*               LISTEN
     -
tcp        0      0 10.2X.4X.4:6642         10.2X.4X.76:57256
ESTABLISHED -
tcp        0      0 10.2X.4X.4:6642         10.2X.4X.134:54026
 ESTABLISHED -
tcp        0      0 10.2X.4X.4:6642         10.2X.4X.10:34962
ESTABLISHED -
tcp        0      0 10.2X.4X.4:6642         10.2X.4X.6:49238
 ESTABLISHED -
tcp        0      0 10.2X.4X.4:6642         10.2X.4X.135:59972
 ESTABLISHED -
tcp        0      0 10.2X.4X.4:6642         10.2X.4X.75:40162
ESTABLISHED -
tcp        0      0 10.2X.4X.4:39566        10.2X.4X.132:6642
ESTABLISHED -
#OVN follower 3

netstat -nap | grep 6642

tcp        0      0 0.0.0.0:6642            0.0.0.0:*               LISTEN
     -
tcp        0      0 10.2X.4X.68:6642        10.2X.4X.70:40750
ESTABLISHED -
tcp        0      0 10.2X.4X.68:6642        10.2X.4X.11:49718
ESTABLISHED -
tcp        0      0 10.2X.4X.68:45632       10.2X.4X.132:6642
ESTABLISHED -
tcp        0      0 10.2X.4X.68:6642        10.2X.4X.16:44816
ESTABLISHED -
tcp        0      0 10.2X.4X.68:6642        10.2X.4X.7:45216
 ESTABLISHED

The issue that we are experiencing is on the neutron-server that
disconnects when there is the ovn leader change (due snapshot like each 8
minutes) and reconnects to the next leader. It breaks the Openstack API
when someone is trying to create a VM at the same time.
First, is my current configuration correct? Should the leader change and
break the neutron side? Or is there some missing configuration?
I was wondering if it is possible to use a LB with VIP and this VIP balance
the connections to the ovn central members and I would reconfigure on the
neutron side only with the VIP and also on the ovs-controllers. Does that
make sense?

Thank you.

Regards,

Tiago Pires
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