PT-KILL(1p)

User Contributed Perl Documentation

PT-KILL(1p)

NAME¶

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

SYNOPSIS¶

Usage: pt-kill [OPTIONS]

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¶

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 kills queries if you use the "--kill" option, so it can 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 <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 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.

--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.

--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.

--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)".

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.

•: 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 <http://www.percona.com/bugs/pt-kill>.

Please report bugs at https://bugs.launchpad.net/percona-toolkit <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/ <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.

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 2.1.2

2012-06-15

perl v5.14.2

Source file:	pt-kill.1p.en.gz (from percona-toolkit 2.1.2-1)
Source last updated:	2012-06-15T21:12:16Z
Converted to HTML:	2017-06-07T16:54:29Z