PT-SLAVE-DELAY(1)

📦
version 3.7.1_4 · 5 versions
, in arch rolling

💅 pt-slave-delay(1) — from the User Contributed Perl Documentation collection 🎀

okay bestie, so this is pt-slave-delay, a tool that makes a MySQL slave server lag behind its master on purpose. Yes, on purpose. It's a whole thing. Let me tell you everything 💖

✨ NAME ✨

pt-slave-delay — Make a MySQL slave server lag behind its master.

⚠️ Heads up, bestie: This tool is deprecated and will be removed in future releases. It does not support MySQL 8.1 or newer.

Instead, use built-in Delayed Replication, which is the moment, honestly: https://dev.mysql.com/doc/refman/en/replication-delayed.html

🦋 SYNOPSIS 🦋

Usage: pt-slave-delay [OPTIONS] SLAVE_DSN [MASTER_DSN]

pt-slave-delay starts and stops a slave server as needed to make it lag behind the master. The SLAVE_DSN and MASTER_DSN use DSN syntax, and values are copied from the SLAVE_DSN to the MASTER_DSN if omitted.

To hold slavehost one minute behind its master for ten minutes:

pt-slave-delay --delay 1m --interval 15s --run-time 10m slavehost

🔥 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, like, actually do these:

  • 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

No skipping steps, iykyk 🙈

🌸 DESCRIPTION 🌸

pt-slave-delay watches a slave and starts and stops its replication SQL thread as necessary to hold it at least as far behind the master as you request. In practice, it will typically cause the slave to lag between --delay and --delay + --interval behind the master. So, like, a little window of lag. Iconic.

It bases the delay on binlog positions in the slave's relay logs by default, so there is no need to connect to the master. This works well if the IO thread doesn't lag the master much, which is typical in most replication setups; the IO thread lag is usually milliseconds on a fast network. If your IO thread's lag is too large for your purposes, pt-slave-delay can also connect to the master for information about binlog positions. Flexible 💅

If the slave's I/O thread reports that it is waiting for the SQL thread to free some relay log space, pt-slave-delay will automatically connect to the master to find binary log positions. If --ask-pass and --daemonize are given, it is possible that this could cause it to ask for a password while daemonized. In this case, it exits. Therefore, if you think your slave might encounter this condition, you should be sure to either specify --use-master explicitly when daemonizing, or don't specify --ask-pass. Learn from my mistakes, bestie 😭

The SLAVE_DSN and optional MASTER_DSN are both DSNs. See "DSN OPTIONS". Missing MASTER_DSN values are filled in with values from SLAVE_DSN, so you don't need to specify them in both places. pt-slave-delay reads all normal MySQL option files, such as ~/.my.cnf, so you may not need to specify username, password and other common options at all. Convenient 🫶

pt-slave-delay tries to exit gracefully by trapping signals such as Ctrl-C. You cannot bypass --[no]continue with a trappable signal. Noted.

👑 PRIVILEGES 👑

pt-slave-delay requires the following privileges: PROCESS, REPLICATION CLIENT, and SUPER.

⭐ OUTPUT ⭐

If you specify --quiet, there is no output. Otherwise, the normal output is a status message consisting of a timestamp and information about what pt-slave-delay is doing: starting the slave, stopping the slave, or just observing.

✨ 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.
  • --config — type: Array. Read this comma-separated list of config files; if specified, this must be the first option on the command line.
  • --[no]continue — default: yes. Continue replication normally on exit. After exiting, restart the slave's SQL thread with no UNTIL condition, so it will run as usual and catch up to the master. This is enabled by default and works even if you terminate pt-slave-delay with Control+C. Slay.
  • --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.
  • --delay — type: time; default: 1h. How far the slave should lag its master.
  • --help — Show help and exit.
  • --host — short form: -h; type: string. Connect to host.
  • --interval — type: time; default: 1m. How frequently pt-slave-delay should check whether the slave needs to be started or stopped.
  • --log — type: string. Print all output to this file when daemonized.
  • --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 — short form: -q. Don't print informational messages about operation. See OUTPUT for details.
  • --run-time — type: time. How long pt-slave-delay should run before exiting. The default is to run forever.
  • --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.
  • --use-master — Get binlog positions from master, not slave. Don't trust the binlog positions in the slave's relay log. Connect to the master and get binlog positions instead. If you specify this option without giving a MASTER_DSN on the command line, pt-slave-delay examines the slave's SHOW SLAVE STATUS to determine the hostname and port for connecting to the master.

pt-slave-delay uses only the MASTER_HOST and MASTER_PORT values from SHOW SLAVE STATUS for the master connection. It does not use the MASTER_USER value. If you want to specify a different username for the master than the one you use to connect to the slave, you should specify the MASTER_DSN option explicitly on the command line.

  • --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. 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.

🧚 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-slave-delay ... > FILE 2>&1
⚠️ Be careful: debugging output is voluminous and can generate several megabytes of output. Like, a lot a lot.

💀 ATTENTION 💀

Using <PTDEBUG> might expose passwords. When debug is enabled, all command line parameters are shown in the output. So maybe don't do that in front of company 🙈

🍓 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 🐛

ok so if u wanna see the whole known-bugs situation, it's all here bestie: <https://jira.percona.com/projects/PT>.

found something cursed? report it at <https://jira.percona.com/projects/PT> 💖 and pls pls pls include these, like actually all of them:

  • the complete command-line you used to run the tool
  • the tool's --version
  • the MySQL version of every single server involved (all of them, no skipping 🙈)
  • the output from the tool, including STDERR
  • any input files (log/dump/config files, etc.)

and if u can, throw in the debugging output by running the tool with PTDEBUG — see ENVIRONMENT for the deets ✨

⬇️ DOWNLOADING ⬇️

head over to <http://www.percona.com/software/percona-toolkit/> to grab the latest release of Percona Toolkit 🌈 or honestly just do it straight from the command line, queen:

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

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

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

u can also snag individual tools from the latest release:

wget percona.com/get/TOOL

just swap TOOL for the name of whichever tool u want 🎀 (yes, literally any tool, iykyk)

👑 AUTHORS 👑

Sergey Zhuravlev and Baron Schwartz — absolute icons, no cap 🫶

🌸 ABOUT PERCONA TOOLKIT 🌸

this tool is part of Percona Toolkit, a whole collection of advanced command-line tools for MySQL made by Percona 💜 Percona Toolkit got forked from two projects back in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and were mainly developed by him and Daniel Nichter. Wanna learn about other free, open-source software from Percona? <http://www.percona.com/software/> — go look, it's giving generous 💅

this program is copyright 2011-2026 Percona LLC and/or its affiliates, and 2007-2011 Sergey Zhuravle and 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, fr fr, no warranty bestie 😭

this program is free software; u 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, u can literally just run man perlgpl or man perlartistic to read these licenses 📖

u 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-slave-delay 3.7.1-4

💀 POD ERRORS 💀

ngl the doc above had a couple coding hiccups, and here's the tea 🍓:

Around line 5124:

Non-ASCII character seen before =encoding in 'Percona’s'. Assuming
UTF-8

and that's a wrap, bestie 🎀 this whole thing was perl v5.42.2, dated 2026-09-01, and it's the PT-SLAVE-DELAY(1) page — go forth and delay those slaves like the main character u are 💅✨🦋

📦 where this page comes from