Man page for mk-deadlock-logger

August 24, 2007 – 5:33 pm

MK-DEADLOCK-LOGGER

Section: User Contributed Perl Documentation (1)
Updated: 2008-06-01
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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 $.

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