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c8ae357341
Lifted long standing limitation to the XA of rolling it back at the
transaction's
connection close even if the XA is prepared.
Prepared XA-transaction is made to sustain connection close or server
restart.
The patch consists of
- binary logging extension to write prepared XA part of
transaction signified with
its XID in a new XA_prepare_log_event. The concusion part -
with Commit or Rollback decision - is logged separately as
Query_log_event.
That is in the binlog the XA consists of two separate group of
events.
That makes the whole XA possibly interweaving in binlog with
other XA:s or regular transaction but with no harm to
replication and data consistency.
Gtid_log_event receives two more flags to identify which of the
two XA phases of the transaction it represents. With either flag
set also XID info is added to the event.
When binlog is ON on the server XID::formatID is
constrained to 4 bytes.
- engines are made aware of the server policy to keep up user
prepared XA:s so they (Innodb, rocksdb) don't roll them back
anymore at their disconnect methods.
- slave applier is refined to cope with two phase logged XA:s
including parallel modes of execution.
This patch does not address crash-safe logging of the new events which
is being addressed by MDEV-21469.
CORNER CASES: read-only, pure myisam, binlog-*, @@skip_log_bin, etc
Are addressed along the following policies.
1. The read-only at reconnect marks XID to fail for future
completion with ER_XA_RBROLLBACK.
2. binlog-* filtered XA when it changes engine data is regarded as
loggable even when nothing got cached for binlog. An empty
XA-prepare group is recorded. Consequent Commit-or-Rollback
succeeds in the Engine(s) as well as recorded into binlog.
3. The same applies to the non-transactional engine XA.
4. @@skip_log_bin=OFF does not record anything at XA-prepare
(obviously), but the completion event is recorded into binlog to
admit inconsistency with slave.
The following actions are taken by the patch.
At XA-prepare:
when empty binlog cache - don't do anything to binlog if RO,
otherwise write empty XA_prepare (assert(binlog-filter case)).
At Disconnect:
when Prepared && RO (=> no binlogging was done)
set Xid_cache_element::error := ER_XA_RBROLLBACK
*keep* XID in the cache, and rollback the transaction.
At XA-"complete":
Discover the error, if any don't binlog the "complete",
return the error to the user.
Kudos
-----
Alexey Botchkov took to drive this work initially.
Sergei Golubchik, Sergei Petrunja, Marko Mäkelä provided a number of
good recommendations.
Sergei Voitovich made a magnificent review and improvements to the code.
They all deserve a bunch of thanks for making this work done!
56 lines
1.7 KiB
C++
56 lines
1.7 KiB
C++
#ifndef XA_INCLUDED
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#define XA_INCLUDED
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/*
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Copyright (c) 2000, 2016, Oracle and/or its affiliates.
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Copyright (c) 2009, 2019, MariaDB Corporation.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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class XID_cache_element;
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enum xa_states
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{
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XA_ACTIVE= 0,
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XA_IDLE,
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XA_PREPARED,
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XA_ROLLBACK_ONLY,
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XA_NO_STATE
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};
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struct XID_STATE {
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XID_cache_element *xid_cache_element;
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bool check_has_uncommitted_xa() const;
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bool is_explicit_XA() const { return xid_cache_element != 0; }
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void set_error(uint error);
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void er_xaer_rmfail() const;
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XID *get_xid() const;
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enum xa_states get_state_code() const;
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};
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void xid_cache_init(void);
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void xid_cache_free(void);
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bool xid_cache_insert(XID *xid);
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bool xid_cache_insert(THD *thd, XID_STATE *xid_state, XID *xid);
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void xid_cache_delete(THD *thd, XID_STATE *xid_state);
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bool trans_xa_start(THD *thd);
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bool trans_xa_end(THD *thd);
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bool trans_xa_prepare(THD *thd);
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bool trans_xa_commit(THD *thd);
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bool trans_xa_rollback(THD *thd);
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bool trans_xa_detach(THD *thd);
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bool mysql_xa_recover(THD *thd);
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#endif /* XA_INCLUDED */
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