In MySQL QA Episode #12, “MySQL is Crashing, now what?,” Roel demonstrated how to collect crash-related information that will help Percona discover what the issue is that you are experiencing, and fix it.
As a Support Engineer I (Sveta) am very happy to see this post – but as a person who better understands writing than recording – I’d like to have same information, in textual form. We discussed it, and decided to do a joint blog post. Hence, this post 🙂
If you haven’t seen the video yet, or you do not have any experience with gdb, core files and crashes, I highly recommend to watch it first.
Once you have an idea of why crashes happen, what to do after it happens in your environment, and how to open a Support issue and/or a bug report, you’re ready for the next step: which information do you need to provide? Note that the more complete and comprehensive information you provide, the quicker the evaluation and potential fix process will go – it’s a win-win situation!
At first we need the MySQL error log file. If possible, please send us the full error log file. Often users like to send only the part which they think is relevant, but the error log file can contain other information, recorded before the crash happened. For example, records about table corruptions, lack of disk space, issues with InnoDB dictionary, etc.
If your error log is quite large, please note it would compress very well using a standard compression tool like gzip. If for some reason you cannot send the full error log file, please sent all lines, written after the words “mysqld: ready for connections” (as seen the last time before the actual crash), until the end of the error log file (alternatively, you can also search for rows, started with word “Version:”). Or, if you use scripts (or mysqld_safe) which automatically restart MySQL Server in case of disaster, obviously please search for the one-previous server start after the crash.
An example which includes an automatic restart as mentioned above:
2015-08-03 14:24:03 9911 [Note] /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld: ready for connections.
Version: '5.6.25-73.1-log' socket: '/tmp/mysql_sandbox21690.sock' port: 21690 Percona Server (GPL), Release 73.1, Revision 07b797f
2015-08-03 14:24:25 7f5b193f9700 InnoDB: Buffer pool(s) load completed at 150803 14:24:25
11:25:12 UTC - mysqld got signal 4 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.
Please help us make Percona Server better by reporting any
bugs at http://bugs.percona.com/
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 348059 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.
Thread pointer: 0x0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
stack_bottom = 0 thread_stack 0x40000
You may download the Percona Server operations manual by visiting
http://www.percona.com/software/percona-server/. You may find information
in the manual which will help you identify the cause of the crash.
150803 14:25:12 mysqld_safe Number of processes running now: 0
150803 14:25:12 mysqld_safe mysqld restarted
/home/sveta/SharedData/Downloads/5.6.25/bin/mysqld: /lib64/libssl.so.1.0.0: no version information available (required by /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld)
/home/sveta/SharedData/Downloads/5.6.25/bin/mysqld: /lib64/libcrypto.so.1.0.0: no version information available (required by /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld)
2015-08-03 14:25:12 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2015-08-03 14:25:12 0 [Note] /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld (mysqld 5.6.25-73.1-log) starting as process 10038 ...
2015-08-03 14:25:12 10038 [Warning] Buffered warning: Changed limits: max_open_files: 1024 (requested 50005)
2015-08-03 14:25:12 10038 [Warning] Buffered warning: Changed limits: max_connections: 214 (requested 10000)
2015-08-03 14:25:12 10038 [Warning] Buffered warning: Changed limits: table_open_cache: 400 (requested 4096)
2015-08-03 14:25:12 10038 [Note] Plugin 'FEDERATED' is disabled.
2015-08-03 14:25:12 10038 [Note] InnoDB: Using atomics to ref count buffer pool pages
2015-08-03 14:25:12 10038 [Note] InnoDB: The InnoDB memory heap is disabled
2015-08-03 14:25:12 10038 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2015-08-03 14:25:12 10038 [Note] InnoDB: Memory barrier is not used
2015-08-03 14:25:12 10038 [Note] InnoDB: Compressed tables use zlib 1.2.3
2015-08-03 14:25:12 10038 [Note] InnoDB: Using Linux native AIO
2015-08-03 14:25:12 10038 [Note] InnoDB: Using CPU crc32 instructions
2015-08-03 14:25:12 10038 [Note] InnoDB: Initializing buffer pool, size = 4.0G
2015-08-03 14:25:13 10038 [Note] InnoDB: Completed initialization of buffer pool
2015-08-03 14:25:13 10038 [Note] InnoDB: Highest supported file format is Barracuda.
2015-08-03 14:25:13 10038 [Note] InnoDB: The log sequence numbers 514865622 and 514865622 in ibdata files do not match the log sequence number 514865742 in the ib_logfiles!
2015-08-03 14:25:13 10038 [Note] InnoDB: Database was not shutdown normally!
2015-08-03 14:25:13 10038 [Note] InnoDB: Starting crash recovery.
2015-08-03 14:25:13 10038 [Note] InnoDB: