mk-kill.1p man page

mk-kill — Kill MySQL queries that match certain criteria.

Synopsis

Usage: mk-kill [OPTION]... [FILE...]

mk-kill kills MySQL connections. mk-kill connects to MySQL and gets queries from SHOW PROCESSLIST if no FILE is given. Else, it reads queries from one or more FILE which contains the output of SHOW PROCESSLIST. If FILE is -, mk-kill reads from STDIN.

Kill queries running longer than 60s:

mk-kill --busy-time 60 --kill

Print, do not kill, queries running longer than 60s:

mk-kill --busy-time 60 --print

Check for sleeping processes and kill them all every 10s:

mk-kill --match-command Sleep --kill --victims all --interval 10

Print all login processes:

mk-kill --match-state login --print --victims all

See which queries in the processlist right now would match:

mysql -e "SHOW PROCESSLIST" | mk-kill --busy-time 60 --print

Risks

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-kill is designed to kill queries if you use the "--kill" option is given, and that might disrupt your database's users, of course. You should test with the <"--print"> option, which is safe, if you're unsure what the tool will do.

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-kill>.

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

Description

mk-kill captures queries from SHOW PROCESSLIST, filters them, and then either kills or prints them. This is also known as a "slow query sniper" in some circles. The idea is to watch for queries that might be consuming too many resources, and kill them.

For brevity, we talk about killing queries, but they may just be printed (or some other future action) depending on what options are given.

Normally mk-kill connects to MySQL to get queries from SHOW PROCESSLIST. Alternatively, it can read SHOW PROCESSLIST output from files. In this case, mk-kill does not connect to MySQL and "--kill" has no effect. You should use "--print" instead when reading files. The ability to read a file (or - for STDIN) allows you to capture SHOW PROCESSLIST and test it later with mk-kill to make sure that your matches kill the proper queries. There are a lot of special rules to follow, such as "don't kill replication threads," so be careful to not kill something important!

Two important options to know are "--busy-time" and "--victims". First, whereas most match/filter options match their corresponding value from SHOW PROCESSLIST (e.g. "--match-command" matches a query's Command value), the Time value is matched by "--busy-time". See also "--interval".

Second, "--victims" controls which matching queries from each class are killed. By default, the matching query with the highest Time value is killed (the oldest query). See the next section, "Group, Match and Kill", for more details.

Usually you need to specify at least one "--match" option, else no queries will match. Or, you can specify "--match-all" to match all queries that aren't ignored by an "--ignore" option.

mk-kill is a work in progress, and there is much more it could do.

Group, Match and Kill

Queries pass through several steps to determine which exactly will be killed (or printed--whatever action is specified). Understanding these steps will help you match precisely the queries you want.

The first step is grouping queries into classes. The "--group-by" option controls grouping. By default, this option has no value so all queries are grouped into one, big default class. All types of matching and filtering (the next step) are applied per-class. Therefore, you may need to group queries in order to match/filter some classes but not others.

The second step is matching. Matching implies filtering since if a query doesn't match some criteria, it is removed from its class. Matching happens for each class. First, queries are filtered from their class by the various "Query Matches" options like "--match-user". Then, entire classes are filtered by the various "Class Matches" options like "--query-count".

The third step is victim selection, that is, which matching queries in each class to kill. This is controlled by the "--victims" option. Although many queries in a class may match, you may only want to kill the oldest query, or all queries, etc.

The forth and final step is to take some action on all matching queries from all classes. The "Actions" options specify which actions will be taken. At this step, there are no more classes, just a single list of queries to kill, print, etc.

Output

If only "--kill" then there is no output. If only "--print" then a timestamped KILL statement if printed for every query that would have been killed, like:

# 2009-07-15T15:04:01 KILL 8 (Query 42 sec) SELECT * FROM huge_table

The line shows a timestamp, the query's Id (8), its Time (42 sec) and its Info (usually the query SQL).

If both "--kill" and "--print" are given, then matching queries are killed and a line for each like the one above is printed.

Any command executed by "--execute-command" is responsible for its own output and logging. After being executed, mk-kill has no control or interaction with the command.

Options

Specify at least one of "--kill", "--kill-query", "--print", "--execute-command" or "--stop".

"--any-busy-time" and "--each-busy-time" are mutually exclusive.

"--kill" and "--kill-query" are mutually exclusive.

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

--ask-pass
Prompt for a password when connecting to MySQL.
--charset
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.
--config
type: Array

Read this comma-separated list of config files; if specified, this must be the first option on the command line.
--daemonize
Fork to the background and detach from the shell. POSIX operating systems only.
--defaults-file
short form: -F; type: string

Only read mysql options from the given file. You must give an absolute pathname.
--group-by
type: string

Apply matches to each class of queries grouped by this SHOW PROCESSLIST column. In addition to the basic columns of SHOW PROCESSLIST (user, host, command, state, etc.), queries can be matched by "fingerprint" which abstracts the SQL query in the "Info" column.

By default, queries are not grouped, so matches and actions apply to all queries. Grouping allows matches and actions to apply to classes of similar queries, if any queries in the class match.

For example, detecting cache stampedes (see "all-but-oldest" under "--victims" for an explanation of that term) requires that queries are grouped by the "arg" attribute. This creates classes of identical queries (stripped of comments). So queries "SELECT c FROM t WHERE id=1" and "SELECT c FROM t WHERE id=1" are grouped into the same class, but query c<"SELECT c FROM t WHERE id=3"> is not identical to the first two queries so it is grouped into another class. Then when "--victims" "all-but-oldest" is specified, all but the oldest query in each class is killed for each class of queries that matches the match criteria.
--help
Show help and exit.
--host
short form: -h; type: string; default: localhost

Connect to host.
--interval
type: time

How often to check for queries to kill. If "--busy-time" is not given, then the default interval is 30 seconds. Else the default is half as often as "--busy-time". If both "--interval" and "--busy-time" are given, then the explicit "--interval" value is used.

See also "--run-time".
--log
type: string

Print all output to this file when daemonized.
--password
short form: -p; type: string

Password to use when connecting.
--pid
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.
--port
short form: -P; type: int

Port number to use for connection.
--[no]strip-comments
default: yes

Remove SQL comments from queries in the Info column of the PROCESSLIST.
--run-time
type: time

How long to run before exiting. By default mk-kill runs forever, or until its process is killed or stopped by the creation of a "--sentinel" file. If this option is specified, mk-kill runs for the specified amount of time and sleeps "--interval" seconds between each check of the PROCESSLIST.
--sentinel
type: string; default: /tmp/mk-kill-sentinel

Exit if this file exists.

The presence of the file specified by "--sentinel" will cause all running instances of mk-kill to exit. You might find this handy to stop cron jobs gracefully if necessary. See also "--stop".
--set-vars
type: string; default: wait_timeout=10000

Set these MySQL variables. Immediately after connecting to MySQL, this string will be appended to SET and executed.
--socket
short form: -S; type: string

Socket file to use for connection.
--stop
Stop running instances by creating the "--sentinel" file.

Causes mk-kill to create the sentinel file specified by "--sentinel" and exit. This should have the effect of stopping all running instances which are watching the same sentinel file.
--user
short form: -u; type: string

User for login if not current user.
--version
Show version and exit.
--victims

type: string; default: oldest

Which of the matching queries in each class will be killed. After classes have been matched/filtered, this option specifies which of the matching queries in each class will be killed (or printed, etc.). The following values are possible:

oldest
Only kill the single oldest query. This is to prevent killing queries that aren't really long-running, they're just long-waiting. This sorts matching queries by Time and kills the one with the highest Time value.
all
Kill all queries in the class.
all-but-oldest
Kill all but the oldest query. This is the inverse of the "oldest" value.

This value can be used to prevent "cache stampedes", the condition where several identical queries are executed and create a backlog while the first query attempts to finish. Since all queries are identical, all but the first query are killed so that it can complete and populate the cache.
--wait-after-kill
type: time

Wait after killing a query, before looking for more to kill. The purpose of this is to give blocked queries a chance to execute, so we don't kill a query that's blocking a bunch of others, and then kill the others immediately afterwards.
--wait-before-kill
type: time

Wait before killing a query. The purpose of this is to give "--execute-command" a chance to see the matching query and gather other MySQL or system information before it's killed.

Query Matches

These options filter queries from their classes. If a query does not match, it is removed from its class. The "--ignore" options take precedence. The matches for command, db, host, etc. correspond to the columns returned by SHOW PROCESSLIST: Command, db, Host, etc. All pattern matches are case-sensitive by default, but they can be made case-insensitive by specifying a regex pattern like "(?i-xsm:select)".

See also "Group, Match and Kill".

--match-all
group: Query Matches

Match all queries that are not ignored. If no ignore options are specified, then every query matches (except replication threads, unless "--replication-threads" is also specified). This option allows you to specify negative matches, i.e. "match every query except..." where the exceptions are defined by specifying various "--ignore" options.

This option is not the same as "--victims" "all". This option matches all queries within a class, whereas "--victims" "all" specifies that all matching queries in a class (however they matched) will be killed. Normally, however, the two are used together because if, for example, you specify "--victims" "oldest", then although all queries may match, only the oldest will be killed.
--busy-time
type: time; group: Query Matches

Match queries that have been running for longer than this time. The queries must be in Command=Query status. This matches a query's Time value as reported by SHOW PROCESSLIST.
--idle-time
type: time; group: Query Matches

Match queries that have been idle/sleeping for longer than this time. The queries must be in Command=Sleep status. This matches a query's Time value as reported by SHOW PROCESSLIST.
--ignore-command
type: string; group: Query Matches

Ignore queries whose Command matches this Perl regex.

See "--match-command".
--ignore-db
type: string; group: Query Matches

Ignore queries whose db (database) matches this Perl regex.

See "--match-db".
--ignore-host
type: string; group: Query Matches

Ignore queries whose Host matches this Perl regex.

See "--match-host".
--ignore-info
type: string; group: Query Matches

Ignore queries whose Info (query) matches this Perl regex.

See "--match-info".
--[no]ignore-self
default: yes; group: Query Matches

Don't kill mk-kill's own connection.
--ignore-state
type: string; group: Query Matches; default: Locked

Ignore queries whose State matches this Perl regex. The default is to keep threads from being killed if they are locked waiting for another thread.

See "--match-state".
--ignore-user
type: string; group: Query Matches

Ignore queries whose user matches this Perl regex.

See "--match-user".
--match-command

type: string; group: Query Matches

Match only queries whose Command matches this Perl regex.

Common Command values are:

Query
Sleep
Binlog Dump
Connect
Delayed insert
Execute
Fetch
Init DB
Kill
Prepare
Processlist
Quit
Reset stmt
Table Dump

See <http://dev.mysql.com/doc/refman/5.1/en/…> for a full list and description of Command values.

--match-db
type: string; group: Query Matches

Match only queries whose db (database) matches this Perl regex.
--match-host
type: string; group: Query Matches

Match only queries whose Host matches this Perl regex.

The Host value often time includes the port like "host:port".
--match-info
type: string; group: Query Matches

Match only queries whose Info (query) matches this Perl regex.

The Info column of the processlist shows the query that is being executed or NULL if no query is being executed.
--match-state

type: string; group: Query Matches

Match only queries whose State matches this Perl regex.

Common State values are:

Locked
login
copy to tmp table
Copying to tmp table
Copying to tmp table on disk
Creating tmp table
executing
Reading from net
Sending data
Sorting for order
Sorting result
Table lock
Updating

See <http://dev.mysql.com/doc/refman/5.1/en/…> for a full list and description of State values.

--match-user
type: string; group: Query Matches

Match only queries whose User matches this Perl regex.
--replication-threads
group: Query Matches

Allow matching and killing replication threads.

By default, matches do not apply to replication threads; i.e. replication threads are completely ignored. Specifying this option allows matches to match (and potentially kill) replication threads on masters and slaves.

Class Matches

These matches apply to entire query classes. Classes are created by specifying the "--group-by" option, else all queries are members of a single, default class.

See also "Group, Match and Kill".

--any-busy-time
type: time; group: Class Matches

Match query class if any query has been running for longer than this time. "Longer than" means that if you specify 10, for example, the class will only match if there's at least one query that has been running for greater than 10 seconds.

See "--each-busy-time" for more details.
--each-busy-time
type: time; group: Class Matches

Match query class if each query has been running for longer than this time. "Longer than" means that if you specify 10, for example, the class will only match if each and every query has been running for greater than 10 seconds.

See also "--any-busy-time" (to match a class if ANY query has been running longer than the specified time) and "--busy-time".
--query-count
type: int; group: Class Matches

Match query class if it has at least this many queries. When queries are grouped into classes by specifying "--group-by", this option causes matches to apply only to classes with at least this many queries. If "--group-by" is not specified then this option causes matches to apply only if there are at least this many queries in the entire SHOW PROCESSLIST.
--verbose
short form: -v

Print information to STDOUT about what is being done.

Actions

These actions are taken for every matching query from all classes. The actions are taken in this order: "--print", "--execute-command", "--kill"/"--kill-query". This order allows "--execute-command" to see the output of "--print" and the query before "--kill"/"--kill-query". This may be helpful because mk-kill does not pass any information to "--execute-command".

See also "Group, Match and Kill".

--execute-command
type: string; group: Actions

Execute this command when a query matches.

After the command is executed, mk-kill has no control over it, so the command is responsible for its own info gathering, logging, interval, etc. The command is executed each time a query matches, so be careful that the command behaves well when multiple instances are ran. No information from mk-kill is passed to the command.

See also "--wait-before-kill".
--kill
group: Actions

Kill the connection for matching queries.

This option makes mk-kill kill the connections (a.k.a. processes, threads) that have matching queries. Use "--kill-query" if you only want to kill individual queries and not their connections.

Unless "--print" is also given, no other information is printed that shows that mk-kill matched and killed a query.

See also "--wait-before-kill" and "--wait-after-kill".
--kill-query
group: Actions

Kill matching queries.

This option makes mk-kill kill matching queries. This requires MySQL 5.0 or newer. Unlike "--kill" which kills the connection for matching queries, this option only kills the query, not its connection.
--print
group: Actions

Print a KILL statement for matching queries; does not actually kill queries.

If you just want to see which queries match and would be killed without actually killing them, specify "--print". To both kill and print matching queries, specify both "--kill" and "--print".

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.

·
A

dsn: charset; copy: yes

Default character set.
·
D

dsn: database; copy: yes

Default database.
·
F

dsn: mysql_read_default_file; copy: yes

Only read default options from the given file
·
h

dsn: host; copy: yes

Connect to host.
·
p

dsn: password; copy: yes

Password to use when connecting.
·
P

dsn: port; copy: yes

Port number to use for connection.
·
S

dsn: mysql_socket; copy: yes

Socket file to use for connection.
·
u

dsn: user; copy: yes

User for login if not current user.

Downloading

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
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.

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

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

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 2009-2011 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 MERCHANTABILITY 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, Daniel Nichter

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.

Version

This manual page documents Ver 0.9.10 Distrib 7540 $Revision: 7531 $.

Info

2011-06-08 perl v5.24.0 User Contributed Perl Documentation