75 lines
2.3 KiB
Plaintext
75 lines
2.3 KiB
Plaintext
Debugging mysqld crashes
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========================
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Author: Michal Marek <mmarek@suse.cz>
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Last modified: 2014-11-21
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Contents
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--------
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1) Query log
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2) Coredumps and Backtraces
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3) Trace files
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In case your MySQL server crashes, here are some hints on what to
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include in a bugreport at https://bugzilla.novell.com/ . Please report
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there only bugs in the MySQL packages packaged by Novell/SUSE, bugs in
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binaries / source provided by MySQL AB should be reported at
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http://bugs.mysql.com/ .
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1) Query log
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------------
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Note: Skip this chapter if you already have an exact query that
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crashes the server
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To find out which query possibly crashed the server, add the following
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line to your /etc/my.cnf into section [mysqld]:
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log=/var/lib/mysql/mysqld-query.log
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Mysqld then will, at some performance cost, log all queries into this
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file. After a server crash, you can examine the queries from the time it
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crashed and try to reproduce the crash with single queries (this might
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not allways work, eg. if the crash is caused by some race condition).
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Note that this log file may become extremly large, so if you decide to
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attach it whole to the bugzilla, don't forget to
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xz -k9 /var/lib/mysql/mysqld-query.log
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and attach the xzipped file instead.
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2) Coredumps and Backtraces
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---------------------------
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Another valuable information for the developers is the backtrace. The
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easies way to get one is to let mysqld produce a coredump. Add the
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following line to your /etc/my.cnf into section [mysqld]:
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core-file
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The core file will be written to the /var/lib/mysql/ directory. I
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suggest setting the kernel variable kernel.core_uses_pid to 1
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sysctl -w kernel.core_uses_pid=1
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so that the coredumps don't overwrite each other if you experience
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multiple crashes.
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After you got the core file, install the gdb and mysql-debuginfo
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packages and run
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gdb /usr/sbin/mysqld /var/lib/mysql/<core>
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(gdb) bt
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Replace the <core> with the actual name of the coredump.
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3) Trace files
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--------------
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The trace file will contain various debug information and function
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calls/returns and will become _extremly_ huge after a while, so don't
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attach it to bugzilla unless requested.
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Add the following line to your /etc/my.cnf into section [mysqld]:
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stack-trace
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The trace file will be then written to /var/lib/mysql directory.
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