On 6/16/26 2:55 PM, Dumitru Ceara via dev wrote: > From: Loke Berne <[email protected]> > > Large scale OVN deployments commonly disable the per-chassis nb_cfg > write-back mechanism by setting options:enable_chassis_nb_cfg_update > to false. With thousands of hypervisors each writing their nb_cfg > completion back to Chassis_Private on every generation, the resulting > write amplification can overload the southbound OVSDB cluster. > Disabling write-back eliminates this pressure but also removes the > only existing signal for measuring how long a northbound change takes > to reach each hypervisor. > > OVN_Northbound already records nb_cfg_timestamp in NB_Global when > ovn-northd advances nb_cfg, but hypervisors connect to the southbound > database only. This patch adds the same timestamp to SB_Global, > written atomically with each nb_cfg update. ovn-controller reads > this value and stores it in the local OVS bridge external_ids as > ovn-nb-cfg-sb-ts alongside the existing ovn-nb-cfg-ts (local > completion time). An external collector such as ovs_exporter can > read both values from the bridge and compute per-chassis propagation > latency histograms without any writes to the southbound database, > keeping measurement overhead independent of fleet size. > > Placing the timestamp in SB_Global rather than requiring collectors > to reach the northbound database means it travels transparently > through any relay or VPN between the southbound cluster and the > hypervisor, naturally including that transit in the measurement. > > Testing: confirmed in OVN sandbox and a two-container central/HV > setup that nb_cfg_timestamp is written to SB_Global on each nb_cfg > advance, propagated to br-int external_ids as ovn-nb-cfg-sb-ts, and > continues to update correctly when enable_chassis_nb_cfg_update is > set to false. > > Signed-off-by: Loke Berne <[email protected]> > Assisted-by: Claude Sonnet 4.6 > ---
Hi Loke, I went ahead and pushed this patch to main. I also added you to the AUTHORS.rst list. Thanks a lot for the contribution! Regards, Dumitru _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
