[ovs-discuss] [ovs-dev] OVN nb-db and sb-db election timer

[Han Zhou]

On Mon, Jul 27, 2020 at 1:40 PM Tony Liu <tonyliu0592 at hotmail.com> wrote:
>
> Hi,
>
> During scaling test, when sb-db is busy, followers believe the leader is
dead and started election
> request. Some inconsistency happens during such leader switch. Two
datapath bindings are created
> for the same logical switch. To avoid such case, I was recommended to
increase election timer x10.
> 4K networks are created successfully with that setting.
>
> Is it necessary to set big election timer for nb-db as well? The nb-db
doesn't seem very busy during
> the test, sb-db is always busy and taking 90+% CPU.
>
NB-DB is usually not busy, but you can still adjust the timer according to
your use case.

> With that big election timer, in case real problem happens, like the
leader node goes down, is it going
> to take a while for the new leader to be elected?
>

Yes, it will take longer to detect real failures when election timer is
bigger. During the gap, control plane operations may be impacted/delayed,
but dataplane is not impacted - what's running will continue working, but
changes during this time will not be reflected until the failover is done.

>
> Thanks!
>
> Tony
>
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