On 2/13/26 03:20, Tiago Pires wrote:
Hi Jun,
On Wed, Feb 11, 2026 at 11:40 PM jun.gu <[email protected]> wrote:
Hi Tiago,
Thank you for your reply.
I have rechecked the OpenFlow bundle behavior, and it seems that commit
https://github.com/ovn-org/ovn/commit/d53c599ed05ea3c708a045a9434875458effa21e
should indeed prevent packet drops during ovn-controller restart. My
previous understanding was incorrect — apologies for the confusion.
By the way, could you share how large the OpenFlow flow table is in your
environment?
It depends on the chassi role, there is a role with an average of a
few hundred thousand OF flows and another role with a few millions of
OF flows.
Regards,
Tiago Pires
Hi Tiago,
Thank you for sharing the information.
We will cherry-pick the related patches into our branch and use the
`ovn-ctl stop_controller --restart` command you suggested to verify the
behavior in our environment when restarting or upgrading ovn-controller.||
Best regards, Jun
Best regards,
Jun
On 2/11/26 03:21, Tiago Pires wrote:
Hi Jun,
On Tue, Feb 10, 2026 at 8:54 AM jun.gu via discuss
<[email protected]> wrote:
Hi,
We are currently observing packet drops when `ovn-controller` restarts.
Our environment is running OVN 21.09 and OVS 2.16.2.
We reviewed commit d53c599ed05ea3c708a045a9434875458effa21e, which
avoids dataplane downtime during the initial flow installation. However,
it appears that this change does not fully eliminate packet drops during
an `ovn-controller` restart, as the flow clearing operation still exists.
We also looked at commit 358b1dd53dcd9dde28f47caa21ea19e755323705, which
ensures that all monitored updates are received before installing flows.
Based on these two commits, we are considering a potential optimization
in `ofctl.c`:
- In `run_S_NEW()`: modify the cookie ID of all existing flows to a
unified value (e.g., `0x1234`).
- In `ofctrl_put()`: remove the `clear flows` and `clear groups` operations.
- In `recv_S_UPDATE_FLOWS()`: delete redundant flows whose cookie ID was
set in `run_S_NEW()`.
The flag ovn-ofctrl-wait-before-clear was launched a few OVN releases
ago (I am not sure if it was OVN 22.03)for this purpose to delay to
clear the flows.
https://github.com/ovn-org/ovn/commit/4a34b878d02464266c2b7ff2779de121b130e065
For me it has worked well since then using
/usr/share/ovn/scripts/ovn-ctl stop_controller --restart and upgrading
the ovn-controller.
Since you are using an old version maybe you could consider upgrading it.
The flag ovn-ofctrl-wait-before-clear was removed recently since there
is another mechanism to handle it.
The goal is to avoid clearing flows during restart while still ensuring
stale flows are properly cleaned up once updated flows are installed.
Please let us know if this approach makes sense. If there are no
objections, we would like to prepare and submit a patch for further
discussion.
Best regards,
Jun
Regards,
Tiago Pires
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