Re: [Tarantool-patches] [PATCH v4 05/12] box: make clear_synchro_queue() write a PROMOTE entry instead of CONFIRM + ROLLBACK

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

Good job on the patch!

See 2 comments below.

> diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
> index c96e497c6..2346331c7 100644
> --- a/src/box/txn_limbo.c
> +++ b/src/box/txn_limbo.c
> @@ -317,19 +317,21 @@ txn_limbo_write_cb(struct journal_entry *entry)
>  }
>  
>  static void
> -txn_limbo_write_synchro(struct txn_limbo *limbo, uint16_t type, int64_t lsn)
> +txn_limbo_write_synchro(struct txn_limbo *limbo, uint16_t type, int64_t lsn,
> +			uint64_t term)
>  {
> -	assert(lsn > 0);
> +	assert(lsn >= 0);
>  
>  	struct synchro_request req = {
>  		.type		= type,
>  		.replica_id	= limbo->owner_id,
>  		.lsn		= lsn,
> +		.term		= term,
>  	};
>  
>  	/*
> -	 * This is a synchronous commit so we can
> -	 * allocate everything on a stack.
> +	 * This is a synchronous commit so we can allocate everything on a
> +	 * stack. Note, that promote body includes synchro body.

1. I think this might be discarded now. They have the same encoder
in this version. Up to you.

>  	 */
>  	char body[XROW_SYNCHRO_BODY_LEN_MAX];
>  	struct xrow_header row;
> @@ -464,6 +466,37 @@ txn_limbo_read_rollback(struct txn_limbo *limbo, int64_t lsn)
>  		box_update_ro_summary();
>  }
>  
> +void
> +txn_limbo_write_promote(struct txn_limbo *limbo, int64_t lsn, uint64_t term)
> +{
> +	limbo->confirmed_lsn = lsn;
> +	limbo->is_in_rollback = true;
> +	/*
> +	 * We make sure that promote is only written once everything this
> +	 * instance has may be confirmed.
> +	 */
> +	struct txn_limbo_entry *e = txn_limbo_last_synchro_entry(limbo);
> +	assert(e == NULL || e->lsn <= lsn);
> +	(void) e;
> +	txn_limbo_write_synchro(limbo, IPROTO_PROMOTE, lsn, term);
> +	limbo->is_in_rollback = false;
> +}
> +
> +/**
> + * Process a PROMOTE request, i.e. confirm all entries <= @req.lsn and rollback all
> + * entries > @req.lsn.

2. For referencing parameters in doxygen style you need to use
'@a <name>'. So it would be '@a req.lsn'.

> + */
> +static void
> +txn_limbo_read_promote(struct txn_limbo *limbo,
> +		       const struct synchro_request *req)
> +{
> +	txn_limbo_read_confirm(limbo, req->lsn);
> +	txn_limbo_read_rollback(limbo, req->lsn + 1);
> +	assert(txn_limbo_is_empty(&txn_limbo));
> +	limbo->owner_id = req->origin_id;
> +	limbo->confirmed_lsn = 0;
> +}