PT-DEADLOCK-LOGGER(1)

📦
version 3.7.1_4 · 5 versions
, in arch rolling

🫶 NAME 🫶

okay so this is pt-deadlock-logger(1) — yes, the User Contributed Perl Documentation page — and the whole vibe is: Log MySQL deadlocks. 💅✨

🌸 SYNOPSIS 🌸

Usage: pt-deadlock-logger [OPTIONS] DSN

pt-deadlock-logger logs information about MySQL deadlocks on the given DSN. The tea gets printed to STDOUT, and you can also save it to a table by specifying --dest. Bestie, this 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 ⚠️

real talk bestie, this part matters 🫶

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. no cap, that's the rule 💅

🦋 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 ✨

Okay bestie, this is the part where the tool gets opinionated. 💅 It takes a bunch of extra command-line arguments — peep the "SYNOPSIS" and the usage info if you want the full tea.

  • --ask-pass — Prompts you for a password when connecting to MySQL. No echoing your secrets into the shell history, icon behavior.
  • --[no]buffer-stdout — default: yes ✨ Turns STDOUT buffering on. Highkey turn this off if you want to watch live progress while piping through output post-processing tools like tee or kubectl logs. Otherwise you're just staring at a blank terminal wondering if it's broken (it's not, it's buffering 🙈).
  • --charset — short form: -A; type: string The default character set. If the value is utf8, it 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. Slay, encoding.
  • --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 (and honestly? main character energy of the worst kind). 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. In and out, no traces. 🫶

  • --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 These are the columns, and yes we're going through every single one because you deserve the full lore:
    • server — The (source) server on which the deadlock occurred. Super useful if you're tracking deadlocks on many servers (rip to you).
    • 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. The tool multiplies them out to be one number. Math but make it fashion.
    • 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. First or it's not happening, bestie.
  • --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. Set it and forget it ✨.
  • --daemonize — Fork to the background and detach from the shell. POSIX operating systems only. Bye bestie, it's got things to do. 🦋
  • --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. Don't be cute with relative paths, it won't work.
  • --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. Convenient! 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. Your table, your rules.

  • --help — Show help and exit. The classic.
  • --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. Forever is a long time, but okay 👑
  • --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 minute run-time. The math is mathing 🧮✨
  • --log — type: string Print all output to this file when daemonized.
  • --mysql_ssl — short form: -s; type: int Create SSL MySQL connection. Secure the bag 🔒
  • --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. The backslash is doing so much work here fr.
  • --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. Self-cleaning, we stan.
  • --port — short form: -P; type: int Port number to use for connection.
  • --quiet — Do not deadlocks 😭 (that's the actual wording, ngl it's giving typo, but the vibe is clear) — only print errors and warnings to STDERR. So no deadlock spam, just the important stuff.
  • --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 default value of 10000. The tool prints a warning and continues if a variable cannot be set. It's not gonna crash out over it 🫶

  • --socket — short form: -S; type: string Socket file to use for connection.
  • --tab — Use tabs to separate columns instead of spaces. For the tab-enjoyers 🎀
  • --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 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 <https://www.percona.com/doc/percona-toolkit/LATEST/version-check.html>.

🌈 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 — do not mix them up bestie, it'll ruin your whole day. 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.
  • s — dsn: mysql_ssl; copy: yes — Create SSL connection.

🌸 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. Like, megabytes. We're not exaggerating, it's giving firehose 🚨

🎀 ATTENTION 🎀

Using <PTDEBUG> might expose passwords. When debug is enabled, all command line parameters are shown in the output. So like… maybe don't paste that debug dump into the group chat 🔥

🌸 SYSTEM REQUIREMENTS 🌸

Okay so before you even think about running this, you need Perl, DBI, DBD::mysql, plus some core packages — but like, any reasonably new version of Perl has those already, bestie. No stress 💅

💀 BUGS 💀

Got beef with the tool? There's a whole list of known bugs over at <https://jira.percona.com/projects/PT> — go check it before you come at us 🙈

Please report bugs at <https://jira.percona.com/projects/PT>. And when you do, bestie, include the following, fr fr, it makes everything so much faster:

  • The complete command-line you used to run the tool — the whole thing, not a vibe-check summary ✨
  • The tool's --version output
  • The MySQL version of every single server involved — all of them, no skipping
  • The output from the tool, including STDERR (yes, the ugly part too)
  • Your input files — log files, dump files, config files, whatever you fed it 🍓
And if you can, pls pls pls include debugging output by running the tool with PTDEBUG — see "ENVIRONMENT" for the deets 🔍

🌈 DOWNLOADING 🌈

Wanna grab the freshest Percona Toolkit? Head to <http://www.percona.com/software/percona-toolkit/> 💖

Or honestly, just do it straight from the command line like the main character you are:

wget percona.com/get/percona-toolkit.tar.gz

wget percona.com/get/percona-toolkit.rpm

wget percona.com/get/percona-toolkit.deb

And if you only want one tool instead of the whole squad? You can do that too:

wget percona.com/get/TOOL

Just swap TOOL for the name of literally any tool. Slay. 🎀

👑 AUTHORS 👑

Baron Schwartz and Daniel Nichter — the icons who made this happen 🫶

🦋 ABOUT PERCONA TOOLKIT 🦋

Real talk: this tool is part of Percona Toolkit, which is a whole collection of advanced command-line tools for MySQL, all developed by Percona. It's giving very useful, ngl.

The lore: Percona Toolkit was forked from two projects back in June, 2011 — Maatkit and Aspersa. Those projects were created by Baron Schwartz and primarily developed by him and Daniel Nichter. So like, legacy code with main character energy ✨

Want to learn about other free, open-source software from Percona? Visit <http://www.percona.com/software/> — there's more where this came from 💜

Okay so legally I have to tell you this and I'm gonna tell you exactly like it is:

This program is copyright 2011-2026 Percona LLC and/or its affiliates, 2007-2011 Baron Schwartz.

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.

Like. No warranty. None. Zero. Zip. If it breaks, that's a you problem bestie 😭 (jk ily, but seriously, no warranty)

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 — go read them, they're lowkey iconic 📜

You should have received a copy of the GNU General Public License, version 2 along with this program; if not, see <https://www.gnu.org/licenses/> 💖

⭐ VERSION ⭐

pt-deadlock-logger 3.7.1-4 — that's the one, that's the version 💅

And that's the whole page, bestie!! 🫶 This beauty is from perl v5.42.2, dated 2026-09-01, and it's the PT-DEADLOCK-LOGGER(1) page — now go forth and log those deadlocks 👑✨

📦 where this page comes from