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mk-deadlock-logger.1p - Man Page

Extract and log MySQL deadlock information.


Usage: mk-deadlock-logger [OPTION...] SOURCE_DSN

mk-deadlock-logger extracts and saves information about the most recent deadlock in a MySQL server.

Print deadlocks on SOURCE_DSN:

   mk-deadlock-logger SOURCE_DSN

Store deadlock information from SOURCE_DSN in test.deadlocks table on SOURCE_DSN (source and destination are the same host):

   mk-deadlock-logger SOURCE_DSN --dest D=test,t=deadlocks

Store deadlock information from SOURCE_DSN in test.deadlocks table on DEST_DSN (source and destination are different hosts):

   mk-deadlock-logger SOURCE_DSN --dest DEST_DSN,D=test,t=deadlocks

Daemonize and check for deadlocks on SOURCE_DSN every 30 seconds for 4 hours:

   mk-deadlock-logger SOURCE_DSN --dest D=test,t=deadlocks --daemonize --run-time 4h --interval 30s


The following section is included to inform users about the potential risks, whether known or unknown, of using this tool.  The two main categories of risks are those created by the nature of the tool (e.g. read-only tools vs. read-write tools) and those created by bugs.

mk-deadlock-logger is a read-only tool unless you specify a "--dest" table. In some cases polling SHOW INNODB STATUS too rapidly can cause extra load on the server.  If you're using it on a production server under very heavy load, you might want to set "--interval" to 30 seconds or more.

At the time of this release, we know of no bugs that could cause serious harm to users.

The authoritative source for updated information is always the online issue tracking system.  Issues that affect this tool will be marked as such.  You can see a list of such issues at the following URL: <http://www.maatkit.org/bugs/mk-deadlock-logger>.

See also "Bugs" for more information on filing bugs and getting help.


mk-deadlock-logger extracts deadlock data from a MySQL server.  Currently only InnoDB deadlock information is available.  You can print the information to standard output, store it in a database table, or both.  If neither "--print" nor "--dest" are given, then the deadlock information is printed by default.  If only "--dest" is given, then the deadlock information is only stored.  If both options are given, then the deadlock information is printed and stored.

The source host can be specified using one of two methods.  The first method is to use at least one of the standard connection-related command line options: "--defaults-file", "--password", "--host", "--port", "--socket" or "--user".  These options only apply to the source host; they cannot be used to specify the destination host.

The second method to specify the source host, or the optional destination host using "--dest", is a DSN.  A DSN is a special syntax that can be either just a hostname (like server.domain.com or, or a key=value,key=value string. Keys are a single letter:

  === =======
  h   Connect to host
  P   Port number to use for connection
  S   Socket file to use for connection
  u   User for login if not current user
  p   Password to use when connecting
  F   Only read default options from the given file

If you omit any values from the destination host DSN, they are filled in with values from the source host, so you don't need to specify them in both places. mk-deadlock-logger reads all normal MySQL option files, such as ~/.my.cnf, so you may not need to specify username, password and other common options at all.


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


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


The date and time of the last detected deadlock.


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


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


How long the transaction was active when the deadlock happened.


The connection's database username.


The connection's host.


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


The database in which the deadlock occurred.


The table on which the deadlock occurred.


The index on which the deadlock occurred.


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


The lock mode of the lock that caused the deadlock.


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


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


The query that caused the deadlock.

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.


This tool accepts additional command-line arguments.  Refer to the "Synopsis" and usage information for details.


Prompt for a password when connecting to MySQL.


short form: -A; type: string

Default character set.  If the value is utf8, sets Perl's binmode on STDOUT to utf8, passes the mysql_enable_utf8 option to DBD::mysql, and runs SET NAMES UTF8 after connecting to MySQL.  Any other value sets binmode on STDOUT without the utf8 layer, and runs SET NAMES after connecting to MySQL.


type: string

Use this table to create a small deadlock.  This usually has the effect of clearing out a huge deadlock, which otherwise consumes the entire output of SHOW INNODB STATUS.  The table must not exist.  mk-deadlock-logger will create it with the following MAGIC_clear_deadlocks structure:

  CREATE TABLE test.deadlock_maker(a INT PRIMARY KEY) ENGINE=InnoDB;

After creating the table and causing a small deadlock, the tool will drop the table again.


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).


type: hash

Output only this comma-separated list of columns.  See "Output" for more details on columns.


type: Array

Read this comma-separated list of config files; if specified, this must be the first option on the command line.


Create the table specified by "--dest".

Normally the "--dest" table is expected to exist already.  This option causes mk-deadlock-logger to create the table automatically using the suggested table structure.


Fork to the background and detach from the shell.  POSIX operating systems only.


short form: -F; type: string

Only read mysql options from the given file.  You must give an absolute pathname.


type: DSN

DSN for where to store deadlocks; specify at least a database (D) and table (t).

Missing values are filled in with the same values from the source host, 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 "--[no]collapse" if you want whitespace collapsed.

The following MAGIC_dest_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)

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


Show help and exit.


short form: -h; type: string

Connect to host.


type: time

How often to check for deadlocks.  If no "--run-time" is specified, mk-deadlock-logger runs forever, checking for deadlocks at every interval. See also "--run-time".


type: string

Print all output to this file when daemonized.


Express IP addresses as integers.


short form: -p; type: string

Password to use when connecting.


type: string

Create the given PID file when daemonized.  The file contains the process ID of the daemonized instance.  The PID file is removed when the daemonized instance exits.  The program checks for the existence of the PID file when starting; if it exists and the process with the matching PID exists, the program exits.


short form: -P; type: int

Port number to use for connection.


Print results on standard output.  See "Output" for more.  By default, enables "--[no]collapse" unless you explicitly disable it.

If "--interval" or "--run-time" is specified, only new deadlocks are printed at each interval.  A fingerprint for each deadlock is created using "--columns" server, ts and thread (even if those columns were not specified by "--columns") and if the current deadlock's fingerprint is different from the last deadlock's fingerprint, then it is printed.


type: time

How long to run before exiting.  By default mk-deadlock-logger runs once, checks for deadlocks, and exits.  If "--run-time" is specified but no "--interval" is specified, a default 1 second interval will be used.


type: string; default: wait_timeout=10000

Set these MySQL variables.  Immediately after connecting to MySQL, this string will be appended to SET and executed.


short form: -S; type: string

Socket file to use for connection.


Print tab-separated columns, instead of aligned.


short form: -u; type: string

User for login if not current user.


Show version and exit.

DSN Options

These DSN options are used to create a DSN.  Each option is given like option=value.  The options are case-sensitive, so P and p are not the same option.  There cannot be whitespace before or after the = and if the value contains whitespace it must be quoted.  DSN options are comma-separated.  See the maatkit manpage for full details.


You can download Maatkit from Google Code at <http://code.google.com/p/maatkit/>, or you can get any of the tools easily with a command like the following:

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


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.


For a list of known bugs see <http://www.maatkit.org/bugs/mk-deadlock-logger>.

Please use Google Code Issues and Groups to report bugs or request support: <http://code.google.com/p/maatkit/>.  You can also join #maatkit on Freenode to discuss 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 2007-2011 Baron Schwartz. Feedback and improvements are welcome.


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.


Baron Schwartz

About Maatkit

This tool is part of Maatkit, a toolkit for power users of MySQL.  Maatkit was created by Baron Schwartz; Baron and Daniel Nichter are the primary code contributors.  Both are employed by Percona.  Financial support for Maatkit development is primarily provided by Percona and its clients.


This manual page documents Ver 1.0.21 Distrib 7540 $Revision: 7477 $.


2024-01-25 perl v5.38.2 User Contributed Perl Documentation