MK-DEADLOCK-LOGGER(1)

NAME
mk-deadlock-logger - Extract and log MySQL deadlock information.

SYNOPSIS
The following examples will print deadlocks, store deadlocks in a database table, and daemonize and check once every 30 seconds for 4 hours, respectively:

 mk-deadlock-logger --print
 mk-deadlock-logger --source u=user,p=pass,h=server --dest D=test,t=deadlocks
 mk-deadlock-logger --dest D=test,t=deadlocks --daemonize -m 4h -i 30s

DESCRIPTION
mk-deadlock-logger extracts deadlock data from a MySQL server (currently only InnoDB deadlock information is available). You can print it to standard output or save it in a database table. By default it does neither.

DOWNLOADING
You can download Maatkit from the Sourceforge website at <http://sourceforge.net/projects/maatkit>, or you can get any of the tools easily with a command like the following:

   wget http://www.maatkit.org/get/toolname
   or
   wget http://www.maatkit.org/trunk/toolname

Where "toolname" can be replaced with the name (or fragment of a name) of any of the Maatkit tools. Once downloaded, they're ready to run; no installation is needed. The first URL gets the latest released version of the tool, and the second gets the latest trunk code from Subversion.

OPTIONS
Specify at least one of "--print" or "--dest".

DSN values in "--dest" default to values from "--source".

--askpass
    Prompt for a password when connecting to MySQL.

--collapse
    short form: -c; negatable: yes

    Collapse whitespace in queries to a single space.

    This might make it easier to inspect on the command line or in a query. By default, whitespace is collapsed when printing with "--print", but not modified when storing to "--dest". (That is, the default is different for each action).

--columns
    short form: -C; type: hash

    Output only this comma-separated list of columns.

    See "OUTPUT" for more details on columns.

--daemonize
    Fork and run in the background; POSIX OSes only.

--dest
    short form: -d; type: DSN

    DSN for where to store deadlocks.

    Specifies a server, database and table in which to store deadlock information, in the same format as "--source". Missing values are filled in with the same values as "--source", so you can usually omit most parts of this argument if you're storing deadlocks on the same server on which they happen.

    By default, whitespace in the query column is left intact; use "--collapse" if you want whitespace collapsed.

    The following table is suggested if you want to store all the information mk-deadlock-logger can extract about deadlocks:

     CREATE TABLE deadlocks (
       server char(20) NOT NULL,
       ts datetime NOT NULL,
       thread int unsigned NOT NULL,
       txn_id bigint unsigned NOT NULL,
       txn_time smallint unsigned NOT NULL,
       user char(16) NOT NULL,
       hostname char(20) NOT NULL,
       ip char(15) NOT NULL, -- alternatively, ip int unsigned NOT NULL
       db char(64) NOT NULL,
       tbl char(64) NOT NULL,
       idx char(64) NOT NULL,
       lock_type char(16) NOT NULL,
       lock_mode char(1) NOT NULL,
       wait_hold char(1) NOT NULL,
       victim tinyint unsigned NOT NULL,
       query text NOT NULL,
       PRIMARY KEY  (server,ts,thread)
     ) ENGINE=InnoDB

    If you use "--columns", you can omit whichever columns you don't want to store.

--interval
    short form: -i; type: time; default: 0s

    How often to check for deadlocks.

--numip
    short form: -n

    Express IP addresses as integers.

--print
    short form: -p

    Print results on standard output.

    See "OUTPUT" for more. By default, enables "--collapse" unless you explicitly disable it.

--setvars
    type: string; default: wait_timeout=10000

    Set these MySQL variables.

    Specify any variables you want to be set immediately after connecting to MySQL. These will be included in a "SET" command.

--source
    short form: -s; type: DSN

    DSN to check for deadlocks; required.

    Specifies how to connect to a server to check for deadlocks.

--tab
    short form: -t

    Print tab-separated columns, instead of aligned.

--time
    short form: -m; type: time

    How long to run before exiting.

INNODB CAVEATS AND DETAILS
InnoDB's output is hard to parse and sometimes there's no way to do it right.

Sometimes not all information (for example, username or IP address) is included in the deadlock information. In this case there's nothing for the script to put in those columns. It may also be the case that the deadlock output is so long (because there were a lot of locks) that the whole thing is truncated.

Though there are usually two transactions involved in a deadlock, there are more locks than that; at a minimum, one more lock than transactions is necessary to create a cycle in the waits-for graph. mk-deadlock-logger prints the transactions (always two in the InnoDB output, even when there are more transactions in the waits-for graph than that) and fills in locks. It prefers waited-for over held when choosing lock information to output, but you can figure out the rest with a moment's thought. If you see one wait-for and one held lock, you're looking at the same lock, so of course you'd prefer to see both wait-for locks and get more information. If the two waited-for locks are not on the same table, more than two transactions were involved in the deadlock.

OUTPUT
You can choose which columns are output and/or saved to "--dest" with the "--columns" argument. The default columns are as follows:

server
    The (source) server on which the deadlock occurred. This might be useful if you're tracking deadlocks on many servers.

ts  The date and time of the last detected deadlock.

thread
    The MySQL thread number, which is the same as the connection ID in SHOW FULL PROCESSLIST.

txn_id
    The InnoDB transaction ID, which InnoDB expresses as two unsigned integers. I have multiplied them out to be one number.

txn_time
    How long the transaction was active when the deadlock happened.

user
    The connection's database username.

hostname
    The connection's host.

ip  The connection's IP address. If you specify "--numip", this is converted to an unsigned integer.

db  The database in which the deadlock occurred.

tbl The table on which the deadlock occurred.

idx The index on which the deadlock occurred.

lock_type
    The lock type the transaction held on the lock that caused the deadlock.

lock_mode
    The lock mode of the lock that caused the deadlock.

wait_hold
    Whether the transaction was waiting for the lock or holding the lock. Usually you will see the two waited-for locks.

victim
    Whether the transaction was selected as the deadlock victim and rolled back.

query
    The query that caused the deadlock.

ENVIRONMENT
The environment variable "MKDEBUG" enables verbose debugging output in all of the Maatkit tools:

   MKDEBUG=1 mk-....

SYSTEM REQUIREMENTS
You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl.

BUGS
Please use the Sourceforge bug tracker, forums, and mailing lists to request support or report bugs: <http://sourceforge.net/projects/maatkit/>.

Please include the complete command-line used to reproduce the problem you are seeing, the version of all MySQL servers involved, the complete output of the tool when run with "--version", and if possible, debugging output produced by running with the "MKDEBUG=1" environment variable.

COPYRIGHT, LICENSE AND WARRANTY
This program is copyright (c) 2007 Baron Schwartz. Feedback and improvements are welcome.

THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2; OR the Perl Artistic License. On UNIX and similar systems, you can issue `man perlgpl' or `man perlartistic' to read these licenses.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.

AUTHOR
Baron Schwartz.

VERSION
This manual page documents Ver 1.0.10 Distrib 1972 $Revision: 1968 $.