On Wed, Dec 17, 2025 at 8:36 AM Ilya Maximets <[email protected]> wrote:
>
> On 12/17/25 3:31 AM, Han Zhou wrote:
> >
> >
> > On Tue, Dec 16, 2025 at 12:34 PM Ilya Maximets <[email protected]
<mailto:[email protected]>> wrote:
> >>
> >> I am not sure how we could receive a pre-vote reply for a term of the
> >> actual vote, but if somehow it does happen, we must not accept it, as
> >> the same server can vote differently in the pre-vote and the real vote
> >> and so we may end up with more than one elected leader.
> >>
> >> Ignore the pre-vote reply during the actual elections and warn the user
> >> if this ever happens, so we could investigate further.
> >>
> >> Found while investigating a report with a cluster with two elected
> >> leaders.  It may not be the cause of the issue and, as stated above,
> >> I'm not even sure if receiving a pre-vote for the actual election term
> >> is possible.  But it's better to cover this case explicitly, as the
> >> flag in the reply is not used today.
> >
> > Thanks Ilya. I can't think of how this could happen either, because a
pre-vote
> > reply for term T should already be rejected by raft_receive_term__() in
> > raft_handle_vote_reply() since we're now at term T+1 for the real vote,
but
> > I agree with this patch as a defensive check.
> >
> > Probably it would be good to add a comment in the code to explain this
is
> > a defensive check for an unknown edge case.
> >
> > Acked-by: Han Zhou <[email protected]>
>
> Thanks!  I can add a comment like this:
>
> +        /* This is mostly a defensive check, as pre-vote and a vote
should
> +         * not happen on the same term.  But we'd like to know if they
do. */
>
> What do you think?
>

LGTM!

> Best regards, Ilya Maximets.
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