pt-kill

NAME

pt-kill - Kill MySQL queries that match certain criteria.

SYNOPSIS

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

pt-kill kills MySQL connections. pt-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 -, pt-kill reads from STDIN.

Kill queries running longer than 60s:

pt-kill --busy-time 60 --kill

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

pt-kill --busy-time 60 --print

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

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

Print all login processes:

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

See which queries in the processlist right now would match:

mysql -e "SHOW PROCESSLIST" | pt-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.

pt-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.percona.com/bugs/pt-kill.

See also “BUGS” for more information on filing bugs and getting help.

DESCRIPTION

pt-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 pt-kill connects to MySQL to get queries from SHOW PROCESSLIST. Alternatively, it can read SHOW PROCESSLIST output from files. In this case, pt-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 pt-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.

pt-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, pt-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.

--run-time

type: time

How long to run before exiting. By default pt-kill runs forever, or until its process is killed or stopped by the creation of a “–sentinel” file. If this option is specified, pt-kill runs for the specified amount of time and sleeps “–interval” seconds between each check of the PROCESSLIST.

--sentinel

type: string; default: /tmp/pt-kill-sentinel

Exit if this file exists.

The presence of the file specified by “–sentinel” will cause all running instances of pt-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 pt-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.

–[no]strip-comments

default: yes

Remove SQL comments from queries in the Info column of the PROCESSLIST.

--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”.

--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 pt-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-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.

--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 pt-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, pt-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 pt-kill is passed to the command.

See also “–wait-before-kill”.

--kill

group: Actions

Kill the connection for matching queries.

This option makes pt-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 pt-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 pt-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 percona-toolkit 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.

ENVIRONMENT

The environment variable PTDEBUG enables verbose debugging output to STDERR. To enable debugging and capture all output to a file, run the tool like:

PTDEBUG=1 pt-kill ... > FILE 2>&1

Be careful: debugging output is voluminous and can generate several megabytes of output.

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.percona.com/bugs/pt-kill.

Please report bugs at https://bugs.launchpad.net/percona-toolkit. Include the following information in your bug report:

* Complete command-line used to run the tool

* Tool “–version”

* MySQL version of all servers involved

* Output from the tool including STDERR

* Input files (log/dump/config files, etc.)

If possible, include debugging output by running the tool with PTDEBUG; see “ENVIRONMENT”.

DOWNLOADING

Visit http://www.percona.com/software/percona-toolkit/ to download the latest release of Percona Toolkit. Or, get the latest release from the command line:

wget percona.com/get/percona-toolkit.tar.gz

wget percona.com/get/percona-toolkit.rpm

wget percona.com/get/percona-toolkit.deb

You can also get individual tools from the latest release:

wget percona.com/get/TOOL

Replace TOOL with the name of any tool.

AUTHORS

Baron Schwartz and Daniel Nichter

ABOUT PERCONA TOOLKIT

This tool is part of Percona Toolkit, a collection of advanced command-line tools developed by Percona for MySQL support and consulting. Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and developed primarily by him and Daniel Nichter, both of whom are employed by Percona. Visit http://www.percona.com/software/ for more software developed by Percona.

VERSION

pt-kill 1.0.2

Percona Toolkit
Call Us
+1-888-316-9775 (USA - Sales)
+1-208-473-2904 (USA - Sales)
+44-208-133-0309 (UK - Sales)
0-800-051-8984 (UK - Sales)
0-800-181-0665 (GER - Sales)
+1-877-862-4316 (Emergency)
+1-855-55TRAIN (Training)
+1-925-271-5054 (Training)

Table Of Contents

Previous topic

pt-index-usage

Next topic

pt-log-player

This Page



© Copyright 2011, Percona Inc.
Except where otherwise noted, this documentation is licensed under the following license:
CC Attribution-ShareAlike 2.0 Generic
Created using Sphinx 1.1.3.
This documentation is developed in Launchpad as part of the Percona Toolkit source code.
If you spotted innacuracies, errors, don't understood it or you think something is missing or should be improved, please file a bug.
]]>