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MDEV-28461 semisync-slave server recovery fails to rollback prepared transaction

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that is not in binlog.

Post-crash recovery of --rpl-semi-sync-slave-enabled server
failed to recognize a transaction in-doubt that needed rolled back.
A prepared-but-not-in-binlog transaction gets committed instead
to possibly create inconsistency with a master (e.g the way it was observed
in the bug report).

The semisync recovery is corrected now with initializing binlog coordinates
of any transaction in-doubt to the maximum offset which is
unreachable.
In effect when a prepared transaction that is not found in binlog
it will be decided to rollback because it's guaranteed to reside
in a truncated tail area of binlog.

Mtr tests are reinforced to cover the described scenario.
This commit is contained in:
Andrei
2022-05-11 13:12:48 +03:00
committed by Sergei Golubchik
parent e03e72234a
commit 98ca71ab28
6 changed files with 119 additions and 25 deletions
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13
sql/handler.h
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@@ -963,6 +963,7 @@ typedef struct xid_t XID;
*/
typedef uint Binlog_file_id;
const Binlog_file_id MAX_binlog_id= UINT_MAX;
const my_off_t MAX_off_t = (~(my_off_t) 0);
/*
Compound binlog-id and byte offset of transaction's first event
in a sequence (e.g the recovery sequence) of binlog files.
@@ -977,14 +978,22 @@ struct xid_recovery_member
my_xid xid;
uint in_engine_prepare; // number of engines that have xid prepared
bool decided_to_commit;
Binlog_offset binlog_coord; // semisync recovery binlog offset
/*
Semisync recovery binlog offset. It's initialized with the maximum
unreachable offset. The max value will remain for any transaction
not found in binlog to yield its rollback decision as it's guaranteed
to be within a truncated tail part of the binlog.
*/
Binlog_offset binlog_coord;
XID *full_xid; // needed by wsrep or past it recovery
decltype(::server_id) server_id; // server id of orginal server
xid_recovery_member(my_xid xid_arg, uint prepare_arg, bool decided_arg,
XID *full_xid_arg, decltype(::server_id) server_id_arg)
: xid(xid_arg), in_engine_prepare(prepare_arg),
decided_to_commit(decided_arg), full_xid(full_xid_arg) , server_id(server_id_arg) {};
decided_to_commit(decided_arg),
binlog_coord(Binlog_offset(MAX_binlog_id, MAX_off_t)),
full_xid(full_xid_arg), server_id(server_id_arg) {};
};
/* for recover() handlerton call */