pt-deadlock-loggerp - Online in the Cloud

PROGRAM:

NAME

pt-deadlock-logger - Log MySQL deadlocks.

SYNOPSIS

Usage: pt-deadlock-logger [OPTIONS] DSN

pt-deadlock-logger logs information about MySQL deadlocks on the given DSN. Information
is printed to "STDOUT", and it can also be saved to a table by specifying "--dest". The
tool runs for forever unless "--run-time" or "--iterations" is specified.

Print deadlocks on host1:

pt-deadlock-logger h=host1

Print deadlocks on host1 once then exit:

pt-deadlock-logger h=host1 --iterations 1

Save deadlocks on host1 to percona_schema.deadlocks on host2:

pt-deadlock-logger h=host1 --dest h=host2,D=percona_schema,t=deadlocks

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-deadlock-logger prints information about MySQL deadlocks by polling and parsing "SHOW
ENGINE INNODB STATUS". When a new deadlock occurs, it's printed to "STDOUT" and, if
specified, saved to "--dest".

Only new deadlocks are printed. A fingerprint for each deadlock is created using the
deadlock's server, ts, and thread values (even if these columns are not specified by
"--columns"). A deadlock is printed if its fingerprint is different than the last
deadlock's fingerprint.

The "--dest" statement uses "INSERT IGNORE" to eliminate duplicate deadlocks, so every
deadlock is saved for every "--iterations".

OUTPUT

New deadlocks are printed to "STDOUT", unless "--quiet" is specified. Errors and warnings
are printed to "STDERR".

See also "--columns" and "--tab".

INNODB CAVEATS AND DETAILS

InnoDB's output is hard to parse and sometimes there's no way to do it right.

Sometimes not all information (for example, username or IP address) is included in the
deadlock information. In this case there's nothing for the tool to put in those columns.
It may also be the case that the deadlock output is so long (because there were a lot of
locks) that the whole thing is truncated.

Though there are usually two transactions involved in a deadlock, there are more locks
than that; at a minimum, one more lock than transactions is necessary to create a cycle in
the waits-for graph. pt-deadlock-logger prints the transactions (always two in the InnoDB
output, even when there are more transactions in the waits-for graph than that) and fills
in locks. It prefers waited-for over held when choosing lock information to output, but
you can figure out the rest with a moment's thought. If you see one wait-for and one held
lock, you're looking at the same lock, so of course you'd prefer to see both wait-for
locks and get more information. If the two waited-for locks are not on the same table,
more than two transactions were involved in the deadlock.

Finally, keep in mind that, because usernames with spaces are not quoted by InnoDB, the
tool will generally misreport the second word of these usernames as the hostname.

OPTIONS

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.

--clear-deadlocks
type: string

Use this table to create a small deadlock. This usually has the effect of clearing
out a huge deadlock, which otherwise consumes the entire output of "SHOW INNODB
STATUS". The table must not exist. pt-deadlock-logger will create it with the
following structure:

CREATE TABLE percona_schema.clear_deadlocks (
a INT PRIMARY KEY
) ENGINE=InnoDB

After creating the table and causing a small deadlock, the tool will drop the table
again.

--columns
type: Array; default: server, ts, thread, txn_id, txn_time, user, hostname, ip, db,
tbl, idx, lock_type, lock_mode, wait_hold, victim, query

The columns are:

server
The (source) server on which the deadlock occurred. This might be useful if
you're tracking deadlocks on many servers.

ts The date and time of the last detected deadlock.

thread
The MySQL thread number, which is the same as the connection ID in SHOW FULL
PROCESSLIST.

txn_id
The InnoDB transaction ID, which InnoDB expresses as two unsigned integers. I
have multiplied them out to be one number.

txn_time
How long the transaction was active when the deadlock happened.

user
The connection's database username.

hostname
The connection's host.

ip The connection's IP address. If you specify "--numeric-ip", this is converted to
an unsigned integer.

db The database in which the deadlock occurred.

tbl The table on which the deadlock occurred.

idx The index on which the deadlock occurred.

lock_type
The lock type the transaction held on the lock that caused the deadlock.

lock_mode
The lock mode of the lock that caused the deadlock.

wait_hold
Whether the transaction was waiting for the lock or holding the lock. Usually you
will see the two waited-for locks.

victim
Whether the transaction was selected as the deadlock victim and rolled back.

query
The query that caused the deadlock.

--config
type: Array

Read this comma-separated list of config files; if specified, this must be the first
option on the command line.

--create-dest-table
Create the table specified by "--dest".

Normally the "--dest" table is expected to exist already. This option causes pt-
deadlock-logger to create the table automatically using the suggested table structure.

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

--database
short form: -D; type: string

Connect to this database.

--defaults-file
short form: -F; type: string

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

--dest
type: DSN

DSN for where to store deadlocks; specify at least a database (D) and table (t).

Missing values are filled in with the same values from the source host, so you can
usually omit most parts of this argument if you're storing deadlocks on the same
server on which they happen.

The following table structure is suggested if you want to store all the information
pt-deadlock-logger can extract about deadlocks:

CREATE TABLE deadlocks (
server char(20) NOT NULL,
ts timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
thread int unsigned NOT NULL,
txn_id bigint unsigned NOT NULL,
txn_time smallint unsigned NOT NULL,
user char(16) NOT NULL,
hostname char(20) NOT NULL,
ip char(15) NOT NULL, -- alternatively, ip int unsigned NOT NULL
db char(64) NOT NULL,
tbl char(64) NOT NULL,
idx char(64) NOT NULL,
lock_type char(16) NOT NULL,
lock_mode char(1) NOT NULL,
wait_hold char(1) NOT NULL,
victim tinyint unsigned NOT NULL,
query text NOT NULL,
PRIMARY KEY (server,ts,thread)
) ENGINE=InnoDB

If you use "--columns", you can omit whichever columns you don't want to store.

--help
Show help and exit.

--host
short form: -h; type: string

Connect to host.

--interval
type: time; default: 30

How often to check for deadlocks. If no "--run-time" is specified, pt-deadlock-logger
runs forever, checking for deadlocks at every interval. See also "--run-time".

--iterations
type: int

How many times to check for deadlocks. By default, this option is undefined which
means an infinite number of iterations. The tool always exits for "--run-time",
regardless of the value specified for this option. For example, the tool will exit
after 1 minute with "--run-time 1m --iterations 4 --interval 30" because 4 iterations
at 30 second intervals would take 2 minutes, longer than the 1 mintue run-time.

--log
type: string

Print all output to this file when daemonized.

--numeric-ip
Express IP addresses as integers.

--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.

--quiet
Do not deadlocks; only print errors and warnings to "STDERR".

--run-time
type: time

How long to run before exiting. By default pt-deadlock-logger runs forever, checking
for deadlocks every "--interval" seconds.

--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.

--tab
Use tabs to separate columns instead of spaces.

--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>.

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.

· t

Table in which to store deadlock information.

· 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-deadlock-logger ... > 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.

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