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MDEV-9519: Data corruption will happen on the Galera cluster size change

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If we have a 2+ node cluster which is replicating from an async master
and the binlog_format is set to STATEMENT and multi-row inserts are executed
on a table with an auto_increment column such that values are automatically
generated by MySQL, then the server node generates wrong auto_increment
values, which are different from what was generated on the async master.

In the title of the MDEV-9519 it was proposed to ban start slave on a Galera
if master binlog_format = statement and wsrep_auto_increment_control = 1,
but the problem can be solved without such a restriction.

The causes and fixes:

1. We need to improve processing of changing the auto-increment values
after changing the cluster size.

2. If wsrep auto_increment_control switched on during operation of
the node, then we should immediately update the auto_increment_increment
and auto_increment_offset global variables, without waiting of the next
invocation of the wsrep_view_handler_cb() callback. In the current version
these variables retain its initial values if wsrep_auto_increment_control
is switched on during operation of the node, which leads to inconsistent
results on the different nodes in some scenarios.

3. If wsrep auto_increment_control switched off during operation of the node,
then we must return the original values of the auto_increment_increment and
auto_increment_offset global variables, as the user has set. To make this
possible, we need to add a "shadow copies" of these variables (which stores
the latest values set by the user).

https://jira.mariadb.org/browse/MDEV-9519
This commit is contained in:
Julius Goryavsky
2019-02-25 23:28:46 +01:00
committed by Jan Lindström
parent 80c3fd184d
commit 2c734c980e
16 changed files with 360 additions and 68 deletions
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10
sql/sql_class.h
View File

@ -569,6 +569,16 @@ typedef struct system_variables
ha_rows max_join_size;
ha_rows expensive_subquery_limit;
ulong auto_increment_increment, auto_increment_offset;
#ifdef WITH_WSREP
/*
Stored values of the auto_increment_increment and auto_increment_offset
that are will be restored when wsrep_auto_increment_control will be set
to 'OFF', because the setting it to 'ON' leads to overwriting of the
original values (which are set by the user) by calculated ones (which
are based on the cluster size):
*/
ulong saved_auto_increment_increment, saved_auto_increment_offset;
#endif /* WITH_WSREP */
uint eq_range_index_dive_limit;
ulong lock_wait_timeout;
ulong join_cache_level;