mk-kill.1p - Man Page
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 theInfo
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 thearg
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/thread-commands.html> 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/general-thread-states.html> 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.
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 $.