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 07/12] box: introduce `box.ctl.demote`
Date: Thu, 22 Jul 2021 01:28:32 +0200
Message-ID: <9ae5765f-ffcb-af66-469b-b0a99d71c331@tarantool.org> (raw)
In-Reply-To: <3b4f7752-f68b-afce-c83a-355bcfbc28cc@tarantool.org>

Thanks for the fixes!

>> 2. On top of this commit and on top of the branch too I tried to
>> promote a candidate and got a strange error in the logs, although
>> the promotion was successful:
>>
>> -- 
>> -- Instance 1
>> -- 
>>
>> -- Step 1
>> box.cfg{
>>      listen = 3313,
>>      election_mode = 'candidate',
>>      replication_synchro_quorum = 2,
>>      replication = {'localhost:3314', 'localhost:3313'}
>> }
>> box.schema.user.grant('guest', 'super')
>>
>>
>> -- 
>> -- Instance 2
>> -- 
>>
>> -- Step 2
>> box.cfg{
>>      listen = 3314,
>>      election_mode = 'voter',
>>      replication_synchro_quorum = 2,
>>      replication = {'localhost:3314', 'localhost:3313'},
>>      read_only = true,
>> }
>>
>> -- Step 3
>> box.cfg{read_only = false, election_mode = 'candidate'}
>>
>> -- Step 4
>> box.ctl.promote()
>>
>> main/112/raft_worker box.cc:1538 E> ER_UNSUPPORTED: box.ctl.promote does not support simultaneous invocations
>> ---
>> ...
> 
> That's because once a candidate becomes the leader, it tries to issue `box.ctl.promote()`, and fails,
> since we're already in `box.ctl.promote()` call.
> I'm not sure how to handle that properly. This doesn't break anything though.

Still, the error message looks really not good. There is an option -
make box_promote() for candidate node just call raft_promote() and set
box_in_promote = false. Then wait for the term outcome. Will it work?
You would need to rebase your patchset on master branch then.

It might be a little easier to do if you apply the diff below. (Warning:
I didn't test it.) The motivation is that one of the main reasons why I
wanted box_promote() simplified was because of the strange meaning of some
flags. In particular, try_wait flag somewhy triggered elections before the
waiting which is super not obvious why. How does 'wait' come to 'elections'?

In the diff I tried to remove these flags entirely. And now you have a
single place in the code of box_promote(), where ELECTION_MODE_CANDIDATE
stuff is handled. Here you could try the proposal I gave above.

====================
diff --git a/src/box/box.cc b/src/box/box.cc
index f68fffcab..e7765b657 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -1698,34 +1698,6 @@ box_issue_demote(uint32_t prev_leader_id, int64_t promote_lsn)
 	assert(txn_limbo_is_empty(&txn_limbo));
 }
 
-/**
- * Check whether this instance may run a promote() and set promote parameters
- * according to its election mode.
- */
-static int
-box_check_promote_election_mode(bool *try_wait, bool *run_elections)
-{
-	switch (box_election_mode) {
-	case ELECTION_MODE_OFF:
-		if (try_wait != NULL)
-			*try_wait = true;
-		break;
-	case ELECTION_MODE_VOTER:
-		assert(box_raft()->state == RAFT_STATE_FOLLOWER);
-		diag_set(ClientError, ER_UNSUPPORTED, "election_mode='voter'",
-			 "manual elections");
-		return -1;
-	case ELECTION_MODE_MANUAL:
-	case ELECTION_MODE_CANDIDATE:
-		if (run_elections != NULL)
-			*run_elections = box_raft()->state != RAFT_STATE_LEADER;
-		break;
-	default:
-		unreachable();
-	}
-	return 0;
-}
-
 /* A guard to block multiple simultaneous promote()/demote() invocations. */
 static bool box_in_promote = false;
 
@@ -1757,27 +1729,35 @@ box_promote(void)
 	if (is_leader)
 		return 0;
 
-	bool run_elections = false;
-	bool try_wait = false;
-
-	if (box_check_promote_election_mode(&try_wait, &run_elections) < 0)
-		return -1;
-
-	int64_t wait_lsn = -1;
-
-	if (run_elections && box_run_elections() < 0)
-		return -1;
-	if (try_wait) {
-		if (box_try_wait_confirm(2 * replication_synchro_timeout) < 0)
+	switch (box_election_mode) {
+	case ELECTION_MODE_OFF:
+		if (box_try_wait_confirm(2 * replication_synchro_timeout) != 0)
+			return -1;
+		if (box_trigger_elections() != 0)
 			return -1;
-		if (box_trigger_elections() < 0)
+		break;
+	case ELECTION_MODE_VOTER:
+		assert(box_raft()->state == RAFT_STATE_FOLLOWER);
+		diag_set(ClientError, ER_UNSUPPORTED, "election_mode='voter'",
+			 "manual elections");
+		return -1;
+	case ELECTION_MODE_MANUAL:
+	case ELECTION_MODE_CANDIDATE:
+		if (box_raft()->state != RAFT_STATE_LEADER &&
+		    box_run_elections() != 0)
 			return -1;
+		break;
+	default:
+		unreachable();
 	}
-	if ((wait_lsn = box_wait_limbo_acked()) < 0)
+	if (box_check_promote_election_mode(&try_wait, &run_elections) < 0)
 		return -1;
 
-	box_issue_promote(txn_limbo.owner_id, wait_lsn);
+	int64_t wait_lsn = box_wait_limbo_acked();
+	if (wait_lsn < 0)
+		return -1;
 
+	box_issue_promote(txn_limbo.owner_id, wait_lsn);
 	return 0;
 }
 
@@ -1804,29 +1784,16 @@ box_demote(void)
 		is_leader = is_leader && box_raft()->state == RAFT_STATE_LEADER;
 	if (!is_leader)
 		return 0;
-
-	bool try_wait = false;
-
-	if (box_check_promote_election_mode(&try_wait, NULL) < 0)
-		return -1;
-
-	int64_t wait_lsn = -1;
-
 	if (box_trigger_elections() < 0)
 		return -1;
-
 	if (box_election_mode != ELECTION_MODE_OFF)
 		return 0;
-
-	if (try_wait &&
-	    box_try_wait_confirm(2 * replication_synchro_timeout) < 0)
+	if (box_try_wait_confirm(2 * replication_synchro_timeout) != 0)
 		return -1;
-
-	if ((wait_lsn = box_wait_limbo_acked()) < 0)
+	int64_t wait_lsn = box_wait_limbo_acked();
+	if (wait_lsn < 0)
 		return -1;
-
 	box_issue_demote(txn_limbo.owner_id, wait_lsn);
-
 	return 0;
 }
 

  reply	other threads:[~2021-07-21 23:28 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
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 [this message]
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=9ae5765f-ffcb-af66-469b-b0a99d71c331@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