MySQL Bugs: #67670: Setting innodb_mirrored_log_groups = 2 leads to server crash

Bug #67670	Setting innodb_mirrored_log_groups = 2 leads to server crash
Submitted:	21 Nov 2012 22:41	Modified:	12 Feb 2013 18:02
Reporter:	Oli Sennhauser	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: InnoDB storage engine	Severity:	S2 (Serious)
Version:	5.6.7	OS:	Linux (Linux laptop3 2.6.32-279.14.1.el6.x86_64 #1 SMP Tue Nov 6 23:43:09 UTC 2012 x86_64 x86_64 x86_64 GNU)
Assigned to:		CPU Architecture:	Any
Tags:	innodb_mirrored_log_groups, server crash

Description:
When innodb_mirrored_log_groups is set to 2 the MySQL server crashes.

How to repeat:
# /etc/my.cnf
[mysqld]
innodb_mirrored_log_groups = 2

----

121121 23:36:43 mysqld_safe Starting mysqld daemon with databases from /home/mysql/data/mysql-5.6.7
121121 23:36:44 [Note] Plugin 'FEDERATED' is disabled.
121121 23:36:44 [ERROR] syntax error in innodb_log_group_home_dir, or a wrong number of mirrored log groups                            
121121 23:36:44 [ERROR] Plugin 'InnoDB' init function returned error.                                                                  
121121 23:36:44 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.                                                       
121121 23:36:44 [ERROR] Unknown/unsupported storage engine: InnoDB                                                                     
121121 23:36:44 [ERROR] Aborting                                                                        22:36:44 UTC - mysqld got signal 11 ;
stack_bottom = 0 thread_stack 0x40000
/home/mysql/product/mysql-5.6.7/bin/mysqld(my_print_stacktrace+0x35)[0x8b47d5]
/home/mysql/product/mysql-5.6.7/bin/mysqld(handle_fatal_signal+0x401)[0x64b181]
/lib64/libpthread.so.0[0x32a5c0f500]
/home/mysql/product/mysql-5.6.7/lib/plugin//innodb_engine.so(register_innodb_cb+0x14)[0x7f8d55487384]
/home/mysql/product/mysql-5.6.7/lib/plugin//innodb_engine.so(+0x9df5)[0x7f8d55486df5]
/home/mysql/product/mysql-5.6.7/lib/plugin/libmemcached.so(init_engine+0xf2)[0x7f8d555b3682]
/home/mysql/product/mysql-5.6.7/lib/plugin/libmemcached.so(daemon_memcached_main+0xfa6)[0x7f8d555a0296]
/lib64/libpthread.so.0[0x32a5c07851]
/lib64/libc.so.6(clone+0x6d)[0x32a54e811d]

Suggested fix:
Catch case and rise a proper error...

Debug binaries do not crash:

...
121122 11:25:08 [Note] Plugin 'FEDERATED' is disabled.
121122 11:25:08 [ERROR] syntax error in innodb_log_group_home_dir, or a wrong number of mirrored log groups
121122 11:25:08 [ERROR] Plugin 'InnoDB' init function returned error.
121122 11:25:08 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
121122 11:25:08 [ERROR] Unknown/unsupported storage engine: InnoDB
121122 11:25:08 [ERROR] Aborting

121122 11:25:08 [Note] Binlog end
121122 11:25:08 [Note] Shutting down plugin 'partition'
...

Looks like 5.6.8-rc (non -debug) also does not crash, just that messages in the error log and it does not start.

Moved to internal bug db for verification by the InnoDB team.

Similar stack trace on 5.6.6 on a different Machine (Ubuntu 10.10 64 bit):

/home/mysql/product/mysql-5.6.6/bin/mysqld(my_print_stacktrace+0x35)[0x8b02c5]
/home/mysql/product/mysql-5.6.6/bin/mysqld(handle_fatal_signal+0x401)[0x64a0d1]
/lib/libpthread.so.0(+0xfb40)[0x7fe18d370b40]
/home/mysql/product/mysql-5.6.6/lib/plugin//innodb_engine.so(register_innodb_cb+0x14)[0x7fe188e9e1c4]
/home/mysql/product/mysql-5.6.6/lib/plugin//innodb_engine.so(+0x9043)[0x7fe188e9e043]
/home/mysql/product/mysql-5.6.6/lib/plugin/libmemcached.so(init_engine+0xf2)[0x7fe188fca662]
/home/mysql/product/mysql-5.6.6/lib/plugin/libmemcached.so(daemon_memcached_main+0xfa6)[0x7fe188fb7276]
/lib/libpthread.so.0(+0x7971)[0x7fe18d368971]
/lib/libc.so.6(clone+0x6d)[0x7fe18c0ddf3d]

Thank you for the report.

Verified as described.

from manual "The number of identical copies of log groups to keep for the database. Always set this value to 1.". Also see http://forums.mysql.com/read.php?35,6243,7320#msg-7320. We should remove this parameter.

Bug#67988 Startup error when innodb_mirrored_log_groups != 1 

was marked as a duplicate.

Note that a fix for this bug is scheduled for an upcoming point release of 5.1/5.5/5.6.

Added to changelog for 5.6.11: 

When innodb_mirrored_log_groups was set to a value other than the
default 1, the MySQL server encountered a serious error during
startup while loading the InnoDB memcached plugin. In earlier
releases, the server would refuse to start (but not display an error)
when this setting was changed. This fix cleans up the error handling
for unsupported values of this configuration option.

The documentation was also clarified that this configuration option is obsolete, has no effect, and should not be used.