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pt-deadlock-logger - Log MySQL deadlocks.



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


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


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.


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

See also --columns and --tab.


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.


This tool accepts additional command-line arguments. Refer to the “SYNOPSIS” and usage information for details.


Prompt for a password when connecting to MySQL.


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.


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 (

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


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:


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


The date and time of the last detected deadlock.


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


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


How long the transaction was active when the deadlock happened.


The connection’s database username.


The connection’s host.


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


The database in which the deadlock occurred.


The table on which the deadlock occurred.


The index on which the deadlock occurred.


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


The lock mode of the lock that caused the deadlock.


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


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


The query that caused the deadlock.


type: Array

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


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.


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


short form: -D; type: string

Connect to this database.


short form: -F; type: string

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


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,
  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)

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


Show help and exit.


short form: -h; type: string

Connect to host.


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.


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.


type: string

Print all output to this file when daemonized.


Express IP addresses as integers.


short form: -p; type: string

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


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.


short form: -P; type: int

Port number to use for connection.


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


type: time

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


type: Array

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

By default, the tool sets:


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.


short form: -S; type: string

Socket file to use for connection.


Use tabs to separate columns instead of spaces.


short form: -u; type: string

User for login if not current user.


Show version and exit.


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


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.


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.


Using <PTDEBUG> might expose passwords. When debug is enabled, all command line parameters are shown in the output.


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


For a list of known bugs, see

Please report bugs at 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”.


Visit to download the latest release of Percona Toolkit. Or, get the latest release from the command line:




You can also get individual tools from the latest release:


Replace TOOL with the name of any tool.


Baron Schwartz and Daniel Nichter


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 to learn about other free, open-source software from Percona.


pt-deadlock-logger 3.5.7