Re: [Tarantool-patches] [PATCH v14 2/6] qsync: update confirmed lsn on initial promote request

[Vladislav Shpilevoy via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Thanks for the patch!

On 10.09.2021 17:29, Cyrill Gorcunov wrote:
> When promote request is handled we drop last confirmed
> lsn to zero because its value make sense for sync queue
> owner only. Still the case where we become queue owner
> for the first time is special - we need to fetch the
> obtained lsn from the request and remember it so we
> will be able to filter any next malformed requests
> with wrong lsn numbers (see queue filtering procedure
> in next patch).

I don't understand anything. Why isn't it needed always? And
how exactly will it help to filter stuff?

> diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
> index cca2ce493..08463219d 100644
> --- a/src/box/txn_limbo.c
> +++ b/src/box/txn_limbo.c
> @@ -521,8 +522,13 @@ txn_limbo_read_promote(struct txn_limbo *limbo, uint32_t replica_id,
>  	txn_limbo_read_rollback(limbo, lsn + 1);
>  	assert(txn_limbo_is_empty(&txn_limbo));
>  	limbo->owner_id = replica_id;
> +	if (likely(limbo->has_initial_promote)) {
> +		limbo->confirmed_lsn = 0;
> +	} else {
> +		limbo->confirmed_lsn = lsn;
> +		limbo->has_initial_promote = true;
> +	}
>  	box_update_ro_summary();
> -	limbo->confirmed_lsn = 0;
>  }