pt-killp - Online in the Cloud

PROGRAM:

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. 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".

--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. 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.

SYSTEM REQUIREMENTS

You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any
reasonably new version of Perl.

Use pt-killp online using onworks.net services