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.

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 databse (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
--password

short form: -p; type: string

Password to use when connecting.

--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.

--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: 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 the version of other programs on the local system in addition to its own version. For example, it checks the version of every MySQL server it connects to, Perl, and the Perl module DBD::mysql. 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.

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/version-check.

--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.

--test-matching

type: array; group: Query Matches

Files with processlist snapshots to test matching options against. Since the matching options can be complex, you can save snapshots of processlist in files, then test matching options against queries in those files.

This option disables --run-time, --interval, and --[no]ignore-self.

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.

  • 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.

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 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.

VERSION

pt-kill 2.2.10

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