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From: Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Serge Petrenko <sergepetrenko@tarantool.org>
Cc: v.shpilevoy@tarantool.org, tarantool-patches@dev.tarantool.org
Subject: Re: [Tarantool-patches] [PATCH v2 2/8] txn_limbo: fix promote term filtering
Date: Fri, 18 Jun 2021 13:31:49 +0300
Message-ID: <YMx2Fc9shnsYNxPm@grain> (raw)
In-Reply-To: <fd53102c6855226eedb14818adecd4a0d2030214.1623963649.git.sergepetrenko@tarantool.org>

On Fri, Jun 18, 2021 at 12:07:36AM +0300, Serge Petrenko wrote:
> txn_limbo_process() used to filter out promote requests whose term was
> equal to the greatest term seen. This wasn't correct for PROMOTE entries
> with term 1.
> 
> Such entries appear after box.ctl.promote() is issued on an instance
> with disabled elections. Every PROMOTE entry from such an instance has
> term 1, but should still be applied. Fix this in the patch.
> 
> Also, when an outdated PROMOTE entry with term smaller than already
> applied from some replica arrived, it wasn't filtered at all. Such a
> situation shouldn't be possible, but fix it as well.
> 
> Part-of #6034
> ---
>  src/box/txn_limbo.c | 22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
> index 51dc2a186..a5d1df00c 100644
> --- a/src/box/txn_limbo.c
> +++ b/src/box/txn_limbo.c
> @@ -665,17 +665,21 @@ txn_limbo_process(struct txn_limbo *limbo, const struct synchro_request *req)
>  {
>  	uint64_t term = req->term;
>  	uint32_t origin = req->origin_id;
> -	if (txn_limbo_replica_term(limbo, origin) < term) {
> +	if (txn_limbo_replica_term(limbo, origin) < term)
>  		vclock_follow(&limbo->promote_term_map, origin, term);
> -		if (term > limbo->promote_greatest_term) {
> -			limbo->promote_greatest_term = term;
> -		} else if (req->type == IPROTO_PROMOTE) {
> -			/*
> -			 * PROMOTE for outdated term. Ignore.
> -			 */
> -			return;
> -		}
> +
> +	if (term > limbo->promote_greatest_term) {
> +		limbo->promote_greatest_term = term;
> +	} else if (req->type == IPROTO_PROMOTE &&
> +		   limbo->promote_greatest_term > 1) {
> +		/* PROMOTE for outdated term. Ignore. */
> +		say_info("RAFT: ignoring PROMOTE request from instance "
> +			 "id %"PRIu32" for term %"PRIu64". Greatest term seen "
> +			 "before (%"PRIu64") is bigger.", origin, term,
> +			 limbo->promote_greatest_term);
> +		return;
>  	}

Serge, here is a moment I don't understand. The promote_term_map
and promote_greatest_term both are zero initially, then we start
accepting requests from the net and previously we've been updating
promote_term_map and promote_greatest_term in same context, iow
promote_term_map is filtering incoming traffic and update
promote_greatest_term with max from promote_term_map, thus
we can denote it as

	if (term > promote_term_map[i]) {
		promote_term_map[i] = term;
		promote_greatest_term = max(promote_greatest_term, term);
	}

thus promote_greatest_term always = max({promote_term_map[i]}), so I don't
understart why say

	uint64_t term = req->term;
	uint32_t origin = req->origin_id;

	if (txn_limbo_replica_term(limbo, origin) < term) {
		vclock_follow(&limbo->promote_term_map, origin, term);
		if (term > limbo->promote_greatest_term)
			limbo->promote_greatest_term = term;
	}

	if (iproto_type_is_promote_request(req->type) &&
	    limbo->promote_greatest_term > 1) {
		/* PROMOTE for outdated term. Ignore. */
		say_info("RAFT: ignoring %s request from instance "
			 "id %"PRIu32" for term %"PRIu64". Greatest term seen "
			 "before (%"PRIu64") is bigger.",
			 iproto_type_name(req->type), origin, term,
			 limbo->promote_greatest_term);
		return;
	}

won't do the trick? Do I miss something obvious here?

  parent reply	other threads:[~2021-06-18 10:31 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-17 21:07 [Tarantool-patches] [PATCH v2 0/8] forbid implicit limbo ownership transition Serge Petrenko via Tarantool-patches
2021-06-17 21:07 ` [Tarantool-patches] [PATCH v2 1/8] replication: always send raft state to subscribers Serge Petrenko via Tarantool-patches
2021-06-17 21:07 ` [Tarantool-patches] [PATCH v2 2/8] txn_limbo: fix promote term filtering Serge Petrenko via Tarantool-patches
2021-06-17 22:05   ` Cyrill Gorcunov via Tarantool-patches
2021-06-18  8:55     ` Serge Petrenko via Tarantool-patches
2021-06-18 10:31   ` Cyrill Gorcunov via Tarantool-patches [this message]
2021-06-21 15:09     ` Serge Petrenko via Tarantool-patches
2021-06-17 21:07 ` [Tarantool-patches] [PATCH v2 3/8] raft: refactor raft_new_term() Serge Petrenko via Tarantool-patches
2021-06-17 21:07 ` [Tarantool-patches] [PATCH v2 4/8] box: make promote always bump the term Serge Petrenko via Tarantool-patches
2021-06-17 21:07 ` [Tarantool-patches] [PATCH v2 5/8] replication: forbid implicit limbo owner transition Serge Petrenko via Tarantool-patches
2021-06-17 21:07 ` [Tarantool-patches] [PATCH v2 6/8] box: introduce `box.ctl.demote` Serge Petrenko via Tarantool-patches
2021-06-17 21:15   ` Serge Petrenko via Tarantool-patches
2021-06-17 21:07 ` [Tarantool-patches] [PATCH v2 7/8] txn_limbo: persist the latest effective promote in snapshot Serge Petrenko via Tarantool-patches
2021-06-17 21:07 ` [Tarantool-patches] [PATCH v2 8/8] replication: send latest effective promote in initial join Serge Petrenko via Tarantool-patches
2021-06-18 13:02 ` [Tarantool-patches] [PATCH v2 0/8] forbid implicit limbo ownership transition Cyrill Gorcunov via Tarantool-patches
2021-06-21 12:11 ` [Tarantool-patches] [PATCH v2 9/8] replication: send current Raft term in join response Serge Petrenko via Tarantool-patches

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