Tarantool development patches archive
 help / color / mirror / Atom feed
From: Vladislav Shpilevoy via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Serge Petrenko <sergepetrenko@tarantool.org>, gorcunov@gmail.com
Cc: tarantool-patches@dev.tarantool.org
Subject: Re: [Tarantool-patches] [PATCH v3 04/12] box: make promote always bump the term
Date: Sun, 4 Jul 2021 14:14:33 +0200
Message-ID: <fe808d3a-823d-22dc-6953-db0325db78a9@tarantool.org> (raw)
In-Reply-To: <46c167f8c9bfe0e35370b0cbf10505d9d4a888ba.1624918077.git.sergepetrenko@tarantool.org>

Thanks for the patch!

Did you think about making it NOP when the node is already a leader
(even in manual/off mode)? The current solution is all good except
that it makes the current leader temporary read-only until it wins
the election again, which looks strange. I would say "unexpected" for
users.

See 4 comments below.

> diff --git a/src/box/box.cc b/src/box/box.cc
> index 6a0950f44..ce37b307d 100644
> --- a/src/box/box.cc
> +++ b/src/box/box.cc
> @@ -1687,16 +1687,19 @@ box_promote(void)
>  			rc = -1;
>  		} else {
>  promote:
> -			/* We cannot possibly get here in a volatile state. */
> -			assert(box_raft()->volatile_term == box_raft()->term);
> -			txn_limbo_write_promote(&txn_limbo, wait_lsn,
> -						box_raft()->term);
> +			if (try_wait) {
> +				raft_new_term(box_raft());
> +				if (box_raft_wait_persisted() < 0)

1. What if during term WAL write another node also started promote,
won the elections and delivered the promote to us? I suppose after
the WAL write we will silently write PROMOTE for the term which
was won by somebody else, right? Can it be covered by a test?

> +					return -1;
> +			}
> +			uint64_t term = box_raft()->term;
> +			txn_limbo_write_promote(&txn_limbo, wait_lsn, term);
>  			struct synchro_request req = {
>  				.type = IPROTO_PROMOTE,
>  				.replica_id = former_leader_id,
>  				.origin_id = instance_id,
>  				.lsn = wait_lsn,
> -				.term = box_raft()->term,
> +				.term = term,
>  			};
>  			txn_limbo_process(&txn_limbo, &req);
>  			assert(txn_limbo_is_empty(&txn_limbo));
> diff --git a/src/box/raft.c b/src/box/raft.c
> index 7f787c0c5..17caf6f54 100644
> --- a/src/box/raft.c
> +++ b/src/box/raft.c
> @@ -354,6 +354,42 @@ box_raft_wait_leader_found(void)
>  	return 0;
>  }
>  
> +struct raft_wait_persisted_data {
> +	struct fiber *waiter;
> +	uint64_t term;
> +};
> +
> +static int
> +box_raft_wait_persisted_f(struct trigger *trig, void *event)
> +{
> +	struct raft *raft = event;
> +	struct raft_wait_persisted_data *data = trig->data;
> +	if (raft->term >= data->term)
> +		fiber_wakeup(data->waiter);
> +	return 0;
> +}
> +
> +int
> +box_raft_wait_persisted(void)
> +{
> +	if (box_raft()->term == box_raft()->volatile_term)

2. Since it only waits for term being persisted, I would rather
call it 'wait_term_persisted'. Because there is also vote, and
you do not look at it.

> +		return 0;
> +	struct raft_wait_persisted_data data = {
> +		.waiter = fiber(),
> +		.term = box_raft()->volatile_term,
> +	};
> +	struct trigger trig;
> +	trigger_create(&trig, box_raft_wait_persisted_f, &data, NULL);
> +	raft_on_update(box_raft(), &trig);
> +	fiber_yield();

3. What about spurious wakeups? I could call fiber.wakeup() from
Lua on this fiber.

> +	trigger_clear(&trig);
> +	if (fiber_is_cancelled()) {
> +		diag_set(FiberIsCancelled);
> +		return -1;
> +	}
> +	return 0;
> +}
> diff --git a/test/replication/gh-4114-local-space-replication.result b/test/replication/gh-4114-local-space-replication.result
> index 9b63a4b99..e71eb60a8 100644
> --- a/test/replication/gh-4114-local-space-replication.result
> +++ b/test/replication/gh-4114-local-space-replication.result
> @@ -45,9 +45,8 @@ test_run:cmd('switch replica')
>   | ---
>   | - true
>   | ...
> -box.info.vclock[0]
> +a = box.info.vclock[0] or 0
>   | ---
> - | - null
>   | ...
>  box.cfg{checkpoint_count=1}
>   | ---
> @@ -77,9 +76,9 @@ box.space.test:insert{3}
>   | - [3]
>   | ...
>  
> -box.info.vclock[0]
> +assert(box.info.vclock[0] == a + 3)
>   | ---
> - | - 3
> + | - true

4. Why do you need these changes? I reverted this test and it passed.

  reply	other threads:[~2021-07-04 12:14 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-28 22:12 [Tarantool-patches] [PATCH v3 00/12] forbid implicit limbo ownership transition Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 01/12] replication: always send raft state to subscribers Serge Petrenko via Tarantool-patches
2021-07-04 12:12   ` Vladislav Shpilevoy via Tarantool-patches
2021-07-09  9:43     ` Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 02/12] txn_limbo: fix promote term filtering Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 03/12] raft: refactor raft_new_term() Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 04/12] box: make promote always bump the term Serge Petrenko via Tarantool-patches
2021-07-04 12:14   ` Vladislav Shpilevoy via Tarantool-patches [this message]
2021-07-14 18:26     ` Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 05/12] replication: forbid implicit limbo owner transition Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 06/12] box: allow calling promote on a candidate Serge Petrenko via Tarantool-patches
2021-07-04 12:14   ` Vladislav Shpilevoy via Tarantool-patches
2021-07-14 18:26     ` Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 07/12] box: introduce `box.ctl.demote` Serge Petrenko via Tarantool-patches
2021-07-04 12:27   ` Vladislav Shpilevoy via Tarantool-patches
2021-07-14 18:28     ` Serge Petrenko via Tarantool-patches
2021-07-21 23:28       ` Vladislav Shpilevoy via Tarantool-patches
2021-07-23  7:44         ` Sergey Petrenko via Tarantool-patches
2021-07-26 23:50           ` Vladislav Shpilevoy via Tarantool-patches
2021-07-29 20:56             ` Sergey Petrenko via Tarantool-patches
2021-08-01 16:19               ` Vladislav Shpilevoy via Tarantool-patches
2021-08-03  7:56                 ` Serge Petrenko via Tarantool-patches
2021-08-03 23:25                   ` Vladislav Shpilevoy via Tarantool-patches
2021-08-04 13:08                     ` Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 08/12] txn_limbo: persist the latest effective promote in snapshot Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 09/12] replication: encode version in JOIN request Serge Petrenko via Tarantool-patches
2021-07-04 12:27   ` Vladislav Shpilevoy via Tarantool-patches
2021-07-14 18:28     ` Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 10/12] replication: add META stage to JOIN Serge Petrenko via Tarantool-patches
2021-07-04 12:28   ` Vladislav Shpilevoy via Tarantool-patches
2021-07-14 18:28     ` Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 11/12] replication: send latest effective promote in initial join Serge Petrenko via Tarantool-patches
2021-07-04 12:28   ` Vladislav Shpilevoy via Tarantool-patches
2021-07-14 18:28     ` Serge Petrenko via Tarantool-patches
2021-06-28 22:12 ` [Tarantool-patches] [PATCH v3 12/12] replication: send current Raft term in join response Serge Petrenko via Tarantool-patches
2021-07-04 12:29   ` Vladislav Shpilevoy via Tarantool-patches
2021-07-14 18:28     ` Serge Petrenko via Tarantool-patches
2021-08-04 22:41 ` [Tarantool-patches] [PATCH v3 00/12] forbid implicit limbo ownership transition Vladislav Shpilevoy via Tarantool-patches
2021-08-06  7:54   ` Vitaliia Ioffe via Tarantool-patches
2021-08-06  8:31 ` Kirill Yukhin via Tarantool-patches
2021-08-08 10:46   ` Vladislav Shpilevoy via Tarantool-patches
2021-08-09  7:14     ` Kirill Yukhin via Tarantool-patches

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=fe808d3a-823d-22dc-6953-db0325db78a9@tarantool.org \
    --to=tarantool-patches@dev.tarantool.org \
    --cc=gorcunov@gmail.com \
    --cc=sergepetrenko@tarantool.org \
    --cc=v.shpilevoy@tarantool.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Tarantool development patches archive

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://lists.tarantool.org/tarantool-patches/0 tarantool-patches/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 tarantool-patches tarantool-patches/ https://lists.tarantool.org/tarantool-patches \
		tarantool-patches@dev.tarantool.org.
	public-inbox-index tarantool-patches

Example config snippet for mirrors.


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git