pt-kill¶

NAME¶

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

SYNOPSIS¶

Usage¶

pt-kill [OPTIONS] [DSN]

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" > proclist.txt
pt-kill --test-matching proclist.txt --busy-time 60 --print

RISKS¶

Percona Toolkit is mature, proven in the real world, and well tested, but all database tools can pose a risk to the system and the database server. Before using this tool, please:

Read the tool’s documentation
Review the tool’s known “BUGS”
Test the tool on a non-production server
Backup your production server and verify the backups

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 with --test-matching 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 not to 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.

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 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.

pt-kill will kill all the queries matching ANY of the specified criteria (logical OR). For example, using:

--busy-time 114 --match-command 'Query|Execute'

will kill all queries having busy-time > 114 OR where the command is Query or Execute

If you want to kill only the queries where busy-time `` 114> ``AND the command is Query or Execute, you need to use “–kill-busy-commands:

--busy-time 114 --kill-busy-commands 'Query|Execute'

OUTPUT¶

If only --kill is given, then there is no output. If only --print is given, 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.

--daemonize and --test-matching 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.

--create-log-table¶

Create the --log-dsn table if it does not exist.

This option causes the table specified by --log-dsn to be created with the default structure shown in the documentation for that option.

--daemonize¶: Fork to the background and detach from the shell. POSIX operating systems only.

--database¶

short form: -D; type: string

The database to use for the connection.

--defaults-file¶

short form: -F; type: string

Only read mysql options from the given file. You must give an absolute pathname.

--filter¶

type: string

Discard events for which this Perl code doesn’t return true.

This option is a string of Perl code or a file containing Perl code that gets compiled into a subroutine with one argument: $event. This is a hashref. If the given value is a readable file, then pt-kill reads the entire file and uses its contents as the code. The file should not contain a shebang (#!/usr/bin/perl) line.

If the code returns true, the chain of callbacks continues; otherwise it ends. The code is the last statement in the subroutine other than return $event. The subroutine template is:

sub { $event = shift; filter && return $event; }

Filters given on the command line are wrapped inside parentheses like like ( filter ). For complex, multi-line filters, you must put the code inside a file so it will not be wrapped inside parentheses. Either way, the filter must produce syntactically valid code given the template. For example, an if-else branch given on the command line would not be valid:

--filter 'if () { } else { }'  # WRONG

Since it’s given on the command line, the if-else branch would be wrapped inside parentheses which is not syntactically valid. So to accomplish something more complex like this would require putting the code in a file, for example filter.txt:

my $event_ok; if (...) { $event_ok=1; } else { $event_ok=0; } $event_ok

Then specify --filter filter.txt to read the code from filter.txt.

If the filter code won’t compile, pt-kill will die with an error. If the filter code does compile, an error may still occur at runtime if the code tries to do something wrong (like pattern match an undefined value). pt-kill does not provide any safeguards so code carefully!

It is permissible for the code to have side effects (to alter $event).

--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.

--log-dsn¶

type: DSN

Store each query killed in this DSN.

The argument specifies a table to store all killed queries. The DSN passed in must have the database (D) and table (t) options. The table must have at least the following columns. You can add more columns for your own special purposes, but they won’t be used by pt-kill. The following CREATE TABLE definition is also used for --create-log-table. MAGIC_create_log_table:

CREATE TABLE kill_log (
   kill_id     int(10) unsigned NOT NULL AUTO_INCREMENT,
   server_id   bigint(4) NOT NULL DEFAULT '0',
   timestamp   DATETIME,
   reason      TEXT,
   kill_error  TEXT,
   Id          bigint(4) NOT NULL DEFAULT '0',
   User        varchar(16) NOT NULL DEFAULT '',
   Host        varchar(64) NOT NULL DEFAULT '',
   db          varchar(64) DEFAULT NULL,
   Command     varchar(16) NOT NULL DEFAULT '',
   Time        int(7) NOT NULL DEFAULT '0',
   State       varchar(64) DEFAULT NULL,
   Info        longtext,
   Time_ms     bigint(21) DEFAULT '0', # NOTE, TODO: currently not used
   PRIMARY KEY (kill_id)
) DEFAULT CHARSET=utf8

--json¶

Prints killed queries as JSON, must be used with --print. For example:

--print --json

The usual plain-text output from --print will not be displayed.

JSON output will be in the format of:

{
   "Command": "Query",
   "Host": "10.0.0.1:9999",
   "Id": 1234,
   "Info": "SELECT SLEEP(5)",
   "State": "User sleep",
   "Time": 10,
   "User": "my_user",
   "Db": "my_db",
   "Kill_Error": "",
   "Digest": "58A43A7DA83F58C1",
   "Reason": "Exceeds busy time\nQuery matches Command spec",
   "Timestamp": "2022-01-01T00:00:00"
}

--json-fields¶

type: string

Specify a list of additional key:value pairs to include in JSON output when using --json, the value of this parameter must be specified in the format of:

--json-fields key1:value1,key2:value2

Any fields specified using --json-fields will be included in the --json output.

For example:

--print --json --json-fields hostname:$(hostname),tag:my_tag

Will result in JSON records being written to “kill_log.json” using this format:

{
   "Command": "Query",
   "Host": "10.0.0.1:9999",
   "Id": 1234,
   "Info": "SELECT SLEEP(5)",
   "State": "User sleep",
   "Time": 10,
   "User": "my_user",
   "Db": "my_db",
   "Kill_Error": "",
   "Digest": "58A43A7DA83F58C1",
   "Reason": "Exceeds busy time\nQuery matches Command spec",
   "Timestamp": "2022-01-01T00:00:00",
   "hostname": "my_host",
   "tag": "my_tag"
}

--password¶

short form: -p; type: string

Password to use when connecting. If password contains commas they must be escaped with a backslash: “exam,ple”

--pid¶

type: string

Create the given PID file. The tool won’t start if the PID file already exists and the PID it contains is different than the current PID. However, if the PID file exists and the PID it contains is no longer running, the tool will overwrite the PID file with the current PID. The PID file is removed automatically when the tool exits.

--port¶

short form: -P; type: int

Port number to use for connection.

--query-id¶

Prints an ID of the query that was just killed. This is equivalent to the “ID” output of pt-query-digest. This allows cross-referencing the output of both tools.

Example:

Query ID 0xE9800998ECF8427E

Note that this is a digest (or hash) of the query’s “fingerprint”, so queries of the same form but with different values will have the same ID. See pt-query-digest for more information.

--rds¶: Denotes the instance in question is on Amazon RDS. By default pt-kill runs the MySQL command “kill” for --kill and “kill query” --kill-query. On RDS these two commands are not available and are replaced by function calls. This option modifies --kill to use “CALL mysql.rds_kill(thread-id)” instead and --kill-query to use “CALL mysql.rds_kill_query(thread-id)”

--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.

--slave-user¶

type: string

Sets the user to be used to connect to the slaves. This parameter allows you to have a different user with less privileges on the slaves but that user must exist on all slaves.

--slave-password¶

type: string

Sets the password to be used to connect to the slaves. It can be used with –slave-user and the password for the user must be the same on all slaves.

--set-vars¶

type: Array

Set the MySQL variables in this comma-separated list of variable=value pairs.

By default, the tool sets:

wait_timeout=10000

Variables specified on the command line override these defaults. For example, specifying --set-vars wait_timeout=500 overrides the defaultvalue of 10000.

The tool prints a warning and continues if a variable cannot be set.

--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.

--[no]version-check¶

default: yes

Check for the latest version of Percona Toolkit, MySQL, and other programs.

This is a standard “check for updates automatically” feature, with two additional features. First, the tool checks its own version and also the versions of the following software: operating system, Percona Monitoring and Management (PMM), MySQL, Perl, MySQL driver for Perl (DBD::mysql), and Percona Toolkit. Second, it checks for and warns about versions with known problems. For example, MySQL 5.5.25 had a critical bug and was re-released as 5.5.25a.

A secure connection to Percona’s Version Check database server is done to perform these checks. Each request is logged by the server, including software version numbers and unique ID of the checked system. The ID is generated by the Percona Toolkit installation script or when the Version Check database call is done for the first time.

Any updates or known problems are printed to STDOUT before the tool’s normal output. This feature should never interfere with the normal operation of the tool.

For more information, visit https://www.percona.com/doc/percona-toolkit/LATEST/version-check.html.

--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).

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.

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.

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. If password contains commas they must be escaped with a backslash: “exam,ple”

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.

t

Table to log actions in, if passed through –log-dsn.

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.

ATTENTION¶

Using <PTDEBUG> might expose passwords. When debug is enabled, all command line parameters are shown in the 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 https://jira.percona.com/projects/PT/issues.

Please report bugs at https://jira.percona.com/projects/PT. 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 for MySQL developed by Percona. Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and primarily developed by him and Daniel Nichter. Visit http://www.percona.com/software/ to learn about other free, open-source software from Percona.

COPYRIGHT, LICENSE, AND WARRANTY¶

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.

VERSION¶

pt-kill 3.6.0

pt-kill¶

NAME¶

SYNOPSIS¶

Usage¶

RISKS¶

DESCRIPTION¶

GROUP, MATCH AND KILL¶

OUTPUT¶

OPTIONS¶

QUERY MATCHES¶

CLASS MATCHES¶

ACTIONS¶

DSN OPTIONS¶

ENVIRONMENT¶

ATTENTION¶

SYSTEM REQUIREMENTS¶

BUGS¶

DOWNLOADING¶

AUTHORS¶

ABOUT PERCONA TOOLKIT¶

COPYRIGHT, LICENSE, AND WARRANTY¶

VERSION¶

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