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103 lines
3.3 KiB
Plaintext
103 lines
3.3 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: 2006-07-31
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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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bzip2 -k /var/lib/mysql/mysqld-query.log
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and attach the bzipped 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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Note: this unfortunatelly doesn't work in SUSE Linux 10.1 and older.
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On these systems, you need to run safe_mysqld directly under user
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mysql:
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su - mysql
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mysqld_safe --socket=/var/lib/mysql/mysql.sock \
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--datadir=/var/lib/mysql --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 mysqld with the mysqld version you used (mysqld, mysqld-max or
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mysqld-debug) and core with the actual name of the coredump.
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3) Trace files
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--------------
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You'll need the mysqld-debug binary from the mysql-debug package to get
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a trace file. Install the mysqld-debug package and the start mysqld
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using following command:
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$ MYSQLD_DEBUG=yes rcmysql start
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Note: The init script doesn't automatically pick up the mysqld-debug
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binary (as it does with mysqld-max), because it is expected to be used
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just temporarily to help solving a particular problem.
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The init script will then start mysqld-debug and add the --core-file,
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--log and --debug options for you. The query log will be stored in
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/var/lib/mysql/myqld-query.log
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and the trace file in
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/var/lib/mysql/mysqld.trace
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If you don't like the options set by the init script, just put your own
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into /etc/my.cnf and the init script will honor it. For information
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about the --debug option, see "The DBUG Package":
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http://dev.mysql.com/doc/refman/5.0/en/the-dbug-package.html .
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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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