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MK-DEADLOCK-LOGGER

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.

OPTIONS

Some options are negatable with −−no.
−−askpass

Prompt for password for connections.

−−collapse

Makes mk-deadlock-logger collapse all 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

Makes mk-deadlock-logger only output and/or save certain columns. See " OUTPUT " for more details.

−−daemonize

Fork to the background and detach from the shell. This probably doesn’t work on Microsoft Windows.

−−dest

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.

−−help

Displays a help message.

−−interval

How frequently mk-deadlock-logger should check for deadlocks.

−−numip

Makes mk-deadlock-logger express IP addresses as integers.

−−print

Makes mk-deadlock-logger print results on standard output. See " OUTPUT " for more. By default, enables "−−collapse" unless you explicitly disable it.

−−setvars

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

−−source

Specifies a connection to a server to check for deadlocks. This argument is specially formatted as a key=value,key=value string. Keys are a single letter:

   KEY MEANING
   === =======
   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
   D   Database to connect to
   t   Table in which to store deadlock information

The ’t’ part only applies to "−−dest". All parts are optional; mk-deadlock-logger will try to read MySQL’s option files to determine how to connect. If you specify a value without an ’=’ character, mk-deadlock-logger will interpret this as a hostname.

−−tab

Makes mk-deadlock-logger output tab-separated columns instead of whitespace-aligning them. See " OUTPUT " for more.

−−time

Causes mk-deadlock-logger to stop after the specified time has elapsed.

−−version

Output version information and exit.

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/>.

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 1.0.9 Distrib 1877 $Revision: 1871 $.

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