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From: Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: tml <tarantool-patches@dev.tarantool.org>
Cc: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Subject: [Tarantool-patches] [PATCH v16 3/3] qsync: track confirmed_lsn upon CONFIRM packet
Date: Wed, 15 Sep 2021 17:50:46 +0300	[thread overview]
Message-ID: <20210915145046.133303-4-gorcunov@gmail.com> (raw)
In-Reply-To: <20210915145046.133303-1-gorcunov@gmail.com>

While been investigating various cluster split-brain scenarios and
trying to gather valid incoming synchro request domains and ranges
we've discovered that limbo::confirmed_lsn updated not dense enough
to cover our needs.

In particular this variable is always updated by a limbo owner upon
write of syncro entry (to a journal) while replica just reads such
record without confirmed_lsn update, so when the replica become a cluster
leader it sends a promote request back to the former leader where the
packet carries zero LSN instead of previous confirmed_lsn and validation
of such packet won't pass.

Note the packet validation is not yet implemented in this patch so it
is rather a preparatory work for future.

Part-of #6036

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
 src/box/txn_limbo.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
index eb9aa7780..959811309 100644
--- a/src/box/txn_limbo.c
+++ b/src/box/txn_limbo.c
@@ -774,6 +774,20 @@ txn_limbo_process_run(struct txn_limbo *limbo,
 	switch (req->type) {
 		txn_limbo_read_confirm(limbo, lsn);
+		/*
+		 * We have to adjust confirmed_lsn according
+		 * to LSN coming from the request. It is because
+		 * we will need to report it as old's limbo owner
+		 * LSN inside PROMOTE requests (if administrator
+		 * or election engine will make us so).
+		 *
+		 * We could update confirmed_lsn on every
+		 * txn_limbo_read_confirm call but this function
+		 * is usually called in a couple with
+		 * txn_limbo_write_confirm, thus to eliminate redundant
+		 * variables update we make so once but explicitly.
+		 */
+		limbo->confirmed_lsn = req->lsn;
 		txn_limbo_read_rollback(limbo, lsn);

  parent reply	other threads:[~2021-09-15 14:52 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-15 14:50 [Tarantool-patches] [PATCH v16 0/3] qsync: implement packet filtering (part 1) Cyrill Gorcunov via Tarantool-patches
2021-09-15 14:50 ` [Tarantool-patches] [PATCH v16 1/3] latch: add latch_is_locked helper Cyrill Gorcunov via Tarantool-patches
2021-09-15 14:50 ` [Tarantool-patches] [PATCH v16 2/3] qsync: order access to the limbo terms Cyrill Gorcunov via Tarantool-patches
2021-09-15 14:50 ` Cyrill Gorcunov via Tarantool-patches [this message]
2021-09-15 22:51 ` [Tarantool-patches] [PATCH v16 0/3] qsync: implement packet filtering (part 1) Vladislav Shpilevoy via Tarantool-patches
2021-09-16 10:50   ` Cyrill Gorcunov via Tarantool-patches
2021-09-20 15:22 ` [Tarantool-patches] [PATCH 4/3] test: add gh-6036-term-order test Cyrill Gorcunov via Tarantool-patches
2021-09-21  8:51   ` Cyrill Gorcunov via Tarantool-patches
2021-09-22 13:00 ` [Tarantool-patches] [PATCH v16 0/3] qsync: implement packet filtering (part 1) Cyrill Gorcunov via Tarantool-patches

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