On 2/5/25 11:50 AM, Aleksandr Smirnov (K2 Cloud) wrote:
> Hi guys,
> 

Hi Aleksandr,

> We experienced some problems with CMS when watching nb_cfg/sb_cfg up.
> A problem is that inappropriate time delay happens between nb_cfg bump 
> and sb_cfg bump.
> A research shows that the reason is double run of northd engine combined 
> with improper sequence of calls
> engine <-> counter update.
> 
> Exactly, making the change in logical network structure combined with 
> nb_cfg bump results in the following
> execution sequence:
> 
> 1. 'update3' notification of changed made in ovn-nbctl
> 2. engine recompute run, (long time here)
> 3. 'transact' request to NB DB + SB DB, send results of engine's work
> 4. 'update3' + 'reply' received. this update3 fires back our changes we 
> just sent to SB DB.
> 5. engine recompute second run, (long time here, because change handles 
> are not implemented in branch-22)
> 6. Call update_sequence_numbers(), sb_cfg is sent to NB DB.
> 
> Thus, time delay between p4 - p6 need to be eliminated.
> 
> For main branch, where all change handlers are implemented, p.5 takes a 
> short time so, problem is not so visible.
> 

Is there a chance that we hit this on main too though?  E.g. when some
of the change handlers fail to incrementally process inputs?

> 
> I have prepared a patch that is going to fix this problem in our 
> environment, made over branch-22.09, see in attachment.
> 

I can't see the attachment (maybe mailman scrubbed it?).

22.09 is not actively supported anymore.  Our currently supported
release branches are: 25.03 (starting next week), 24.09 and 24.03 LTS.
22.03 LTS is supported only for critical security fixes.

https://www.ovn.org/en/releases/all_releases/

So, do you think your patch will be beneficial on branch-24.0x too?

> So guys, if you want to have it in official ovn repo, let me know, I 
> will post the patch to patchwork.
> 
> best regards,
> 
> Alexander
> 

Regards,
Dumitru

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