[Tarantool-patches] [PATCH 2/2] election: during bootstrap prefer candidates

[Vladislav Shpilevoy]

Thanks for the review!

>> diff --git a/src/box/box.cc b/src/box/box.cc
>> index ef3efe3e0..3105b04b6 100644
>> --- a/src/box/box.cc
>> +++ b/src/box/box.cc
>> @@ -3519,7 +3519,30 @@ box_cfg_xc(void)
>>            * should take the control over the situation and start a new
>>            * term immediately.
>>            */
>> -        raft_new_term(box_raft());
>> +        struct raft *raft = box_raft();
>> +        if (box_election_mode == ELECTION_MODE_MANUAL) {
>> +            raft_start_candidate(raft);
>> +            raft_new_term(raft);
>> +            int rc = box_raft_wait_leader_found();
>> +            /*
>> +             * No need to check if the mode is still manual - it
>> +             * couldn't change because box.cfg is protected with a
>> +             * fiber lock.
>> +             */
>> +            assert(box_election_mode == ELECTION_MODE_MANUAL);
>> +            raft_stop_candidate(raft, false);
>> +            /*
>> +             * It should not fail, because on bootstrap the node is
>> +             * a single registered instance. It can't not win the
>> +             * elections while being a lone participant. But still
>> +             * check the result so as not to a ignore potential
>> +             * problems.
>> +             */
>> +            if (rc != 0)
>> +                diag_raise();
>> +        } else {
>> +            raft_new_term(raft);
>> +        }
> 
> Could you please extract this fix into a separate commit?

Done. See v2.

> Speaking of your problems with raft_try_candidate. I also can't think
> of a good enough alternative.
> 
> For promote it would be nice to do:
> 
> do {
>     raft_try_candidate_for_1_term();
> } while (leader is not known);
> 
> and simply
> raft_try_candidate_for_1_term();
> for bootstrap.
> 
> But raft_try_candidate_for_1_term() looks hard to implement.
Yes, I had something like that in mind too. I tried to
implement it in v2.