PT-SLAVE-RESTART(1)

📦
version 3.7.1_4 · 6 versions
, in arch rolling

okay so bestie, you're looking at PT-SLAVE-RESTART(1) — yep, the User Contributed Perl Documentation for pt-replica-restart — and I'm gonna walk you through it with all the facts intact. no cap. 💅

NAME 🌸

pt-replica-restart — Watch and restart MySQL replication after errors.

SYNOPSIS 🚀

Usage: pt-replica-restart [OPTIONS] [DSN]

pt-replica-restart watches one or more MySQL replication replicas for errors, and tries to restart replication if it stops.

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-replica-restart watches one or more MySQL replication replicas and tries to skip statements that cause errors. It polls replicas intelligently with an exponentially varying sleep time. You can specify errors to skip and run the replicas until a certain binlog position.

Although this tool can help a replica advance past errors, you should not rely on it to "fix" replication. If replica errors occur frequently or unexpectedly, you should identify and fix the root cause. periodt. 💅

OUTPUT 🎀

pt-replica-restart prints a line every time it sees the replica has an error. By default this line is: a timestamp, connection information, relay_log_file, relay_log_pos, and last_errno. You can add more information using the --verbose option. You can suppress all output using the --quiet option.

SLEEP 😴

pt-replica-restart sleeps intelligently between polling the replica. The current sleep time varies.

  • The initial sleep time is given by --sleep.
  • If it checks and finds an error, it halves the previous sleep time.
  • If it finds no error, it doubles the previous sleep time.
  • The sleep time is bounded below by --min-sleep and above by --max-sleep.
  • Immediately after finding an error, pt-replica-restart assumes another error is very likely to happen next, so it sleeps the current sleep time or the initial sleep time, whichever is less.

GLOBAL TRANSACTION IDS 🌈

As of Percona Toolkit 2.2.8, pt-replica-restart supports Global Transaction IDs introduced in MySQL 5.6.5. It's important to keep in mind that:

  • pt-replica-restart will not skip transactions when multiple replication threads are being used (replica_parallel_workers > 0). pt-replica-restart does not know what the GTID event is of the failed transaction of a specific replica thread.
  • The default behavior is to skip the next transaction from the replica's source. Writes can originate on different servers, each with their own UUID.

See --source-uuid.

EXIT STATUS 👑

An exit status of 0 (sometimes also called a return value or return code) indicates success. Any other value represents the exit status of the Perl process itself, or of the last forked process that exited if there were multiple servers to monitor.

COMPATIBILITY 🧚

pt-replica-restart should work on many versions of MySQL. Lettercase of many output columns from SHOW REPLICA STATUS has changed over time, so it treats them all as lowercase.

OPTIONS ✨

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

  • --always — Start replicas even when there is no error. With this option enabled, pt-replica-restart will not let you stop the replica manually if you want to!
  • --ask-pass — Prompt for a password when connecting to MySQL.
  • --[no]buffer-stdout — default: yes. Enables STDOUT buffering. Disable this option if you want to see live progress when using output post-processing tools such as tee or kubectl logs.
  • --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.
  • --[no]check-relay-log — default: yes. Check the last relay log file and position before checking for replica errors. By default pt-replica-restart will not do anything (it will just sleep) if neither the relay log file nor the relay log position have changed since the last check. This prevents infinite loops (i.e. restarting the same error in the same relay log file at the same relay log position). For certain replica errors, however, this check needs to be disabled by specifying --no-check-relay-log. Do not do this unless you know what you are doing!
  • --config — type: Array. Read this comma-separated list of config files; if specified, this must be the first option on the command line.
  • --daemonize — Fork to the background and detach from the shell. POSIX operating systems only.
  • --database — short form: -D; type: string. Database to use.
  • --defaults-file — short form: -F; type: string. Only read mysql options from the given file. You must give an absolute pathname.
  • --error-length — type: int. Max length of error message to print. When --verbose is set high enough to print the error, this option will truncate the error text to the specified length. This can be useful to prevent wrapping on the terminal.
  • --error-numbers — type: hash. Only restart this comma-separated list of errors. Makes pt-replica-restart only try to restart if the error number is in this comma-separated list of errors. If it sees an error not in the list, it will exit. The error number is in the last_errno column of SHOW REPLICA STATUS.
  • --error-text — type: string. Only restart errors that match this pattern. A Perl regular expression against which the error text, if any, is matched. If the error text exists and matches, pt-replica-restart will try to restart the replica. If it exists but doesn't match, pt-replica-restart will exit. The error text is in the last_error column of SHOW REPLICA STATUS.
  • --help — Show help and exit.
  • --host — short form: -h; type: string. Connect to host.
  • --log — type: string. Print all output to this file when daemonized.
  • --master-uuid — type: string. This option is deprecated and will be removed in future releases. Use --source-user instead.
  • --max-sleep — type: float; default: 64. Maximum sleep seconds. The maximum time pt-replica-restart will sleep before polling the replica again. This is also the time that pt-replica-restart will wait for all other running instances to quit if both --stop and --monitor are specified. See SLEEP.
  • --min-sleep — type: float; default: 0.015625. The minimum time pt-replica-restart will sleep before polling the replica again. See SLEEP.
  • --monitor — Whether to monitor the replica (default). Unless you specify --monitor explicitly, --stop will disable it.
  • --mysql_ssl — short form: -s; type: int. Create SSL MySQL connection.
  • --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. Suppresses normal output (disables --verbose).
  • --recurse — type: int; default: 0. Watch replicas of the specified server, up to the specified number of servers deep in the hierarchy. The default depth of 0 means "just watch the replica specified." pt-replica-restart examines SHOW PROCESSLIST and tries to determine which connections are from replicas, then connect to them. See --recursion-method. Recursion works by finding all replicas when the program starts, then watching them. If there is more than one replica, pt-replica-restart uses fork() to monitor them. This also works if you have configured your replicas to show up in SHOW REPLICAS. The minimal configuration for this is the report_host parameter, but there are other report parameters as well for the port, username, and password.
  • --recursion-method — type: array; default: processlist,hosts. Preferred recursion method used to find replicas.

Possible methods are:

  • processlist — uses SHOW PROCESSLIST
  • hosts — uses SHOW REPLICAS (SHOW SLAVE HOSTS before MySQL 8.1)
  • none — Do not find replicas

The processlist method is preferred because SHOW REPLICAS is not reliable. However, the hosts method is required if the server uses a non-standard port (not 3306). Usually pt-replica-restart does the right thing and finds the replicas, but you may give a preferred method and it will be used first. If it doesn't find any replicas, the other methods will be tried.

  • --run-time — type: time. Time to run before exiting. Causes pt-replica-restart to stop after the specified time has elapsed. Optional suffix: s=seconds, m=minutes, h=hours, d=days; if no suffix, s is used.
  • --sentinel — type: string; default: /tmp/pt-replica-restart-sentinel. Exit if this file exists.
  • --slave-user — type: string. This option is deprecated and will be removed in future releases. Use --replica-user instead.
  • --slave-password — type: string. This option is deprecated and will be removed in future releases. Use --replica-password instead.
  • --replica-user — type: string. Sets the user to be used to connect to the replicas. This parameter allows you to have a different user with less privileges on the replicas but that user must exist on all replicas.
  • --replica-password — type: string.
  • --replica-password — sets the password used to connect to the replicas 💖. It pairs with --replica-user, and heads up: the password for that user has to be the same on every single replica, no cap.
  • --set-vars — type: Array 🌸

Sets the MySQL variables from this comma-separated list of "variable=value" pairs.

Out of the box the tool sets:

wait_timeout=10000

Anything you pass on the command line overrides those defaults. Like, if you do --set-vars wait_timeout=500, boom, the default 10000 is gone, bestie.

If a variable just refuses to be set, the tool prints a warning and keeps it moving. Iconic resilience tbh.

  • --skip-count — type: int; default: 1 ✨

How many statements to skip when restarting the replica.

  • --source-uuid — type: string 🦋

When you're using GTID, the tool needs to create an empty transaction in order to skip it. But if writes are coming from different nodes up in the replication tree, there's genuinely no way to know which event from which UUID to skip. Messy.

By default, it skips transactions from the replica's source ('Source_UUID' from "SHOW REPLICA STATUS"). 💅

So like, with this setup:

source1 -> replica1 -> replica2

when you're skipping events on replica2 that were actually written to source1, you must specify the UUID of source1 — otherwise the tool just uses the UUID of replica1 by default. Not the vibe you want.

See "GLOBAL TRANSACTION IDS".

  • --sleep — type: int; default: 1 🎀

The initial number of seconds to sleep between checks on the replica.

See "SLEEP".

  • --socket — short form: -S; type: string 🧚

Socket file to use for the connection.

  • --stop — stop running instances by creating the sentinel file 🛑

This makes "pt-replica-restart" create the sentinel file specified by "--sentinel". The whole point: it should effectively stop every running instance that's watching that same sentinel file. If "--monitor" isn't specified, "pt-replica-restart" just exits after creating the file. If "--monitor" is specified, it waits out the interval given by "--max-sleep", removes the file, and then continues working. 💫

This is honestly so handy for stopping cron jobs gracefully when you need to, or for swapping one running instance out for another. Example: say you want to stop and restart "pt-replica-restart" every hour — just to make sure it gets restarted hourly in case of a server crash or some other chaos — you'd use a "crontab" line like:

0 * * * * pt-replica-restart --monitor --stop --sentinel /tmp/pt-replica-restartup

Using a non-default "--sentinel" guarantees the hourly "cron" job only stops instances that were previously started with those same options (aka from that same "cron" job). Clean. ✨

See also "--sentinel".

  • --until-master — type: string ⚠️

Deprecated, bestie. It's getting removed in future releases. Use "--until-source" instead.

  • --until-source — type: string 💜

Runs until this source binary log file and position. So: start the replica, and retry if it fails, until it reaches the given replication coordinates. Those coordinates are the logfile and position on the source, given by relay_source_log_file, exec_source_log_pos. The argument has to be in the format "file,pos" — separate the filename and position with a single comma and no space. Periodt.

This also causes an UNTIL clause to be handed to START REPLICA.

Once it reaches that point, the replica should be stopped and pt-replica-restart exits. 🏁

  • --until-relay — type: string 🌈

Runs until this relay log file and position. Same energy as "--until-source", except it's in the replica's relay logs. The coordinates come from relay_log_file, relay_log_pos.

  • --user — short form: -u; type: string 🫶

User for login if you're not the current user.

  • --verbose — short form: -v; cumulative: yes; default: 1 💬

Adds more info to the output. You can stack this flag multiple times, like -v -v OR -vv. The tiers are:

  • By default (no verbose flag): the tool outputs connection information, a timestamp, relay_log_file, relay_log_pos, and last_errno.
  • One flag (-v): adds last_error. See also "--error-length".
  • Two flags (-vv): prints the current sleep time every time pt-replica-restart sleeps.

Want zero output at all? Use the "--quiet" option. 🤫

  • --version — Show version and exit.
  • --[no]version-check — default: yes ⭐

Checks for the latest version of Percona Toolkit, MySQL, and other programs.

It's your standard "check for updates automatically" feature, except with two extra layers. First, the tool checks its own version and the versions of: the operating system, Percona Monitoring and Management (PMM), MySQL, Perl, the MySQL driver for Perl (DBD::mysql), and Percona Toolkit. Second, it checks for and warns you about versions with known problems. For example, MySQL 5.5.25 had a critical bug and got re-released as 5.5.25a.

To run these checks it makes a secure connection to Percona's Version Check database server. Every request gets logged by the server, including software version numbers and the unique ID of the checked system. That ID is generated by the Percona Toolkit installation script, or when the Version Check database call happens for the first time. 🙈

Any updates or known problems get printed to STDOUT before the tool's normal output. This feature should never interfere with normal operation, fr fr.

For more information, visit <https://www.percona.com/doc/percona-toolkit/LATEST/version-check.html>.

Yeah, and then the page just... says "Show version and exit." again at the end of the options. That's not me, that's literally what's in there. 💀 Consider it --version's encore.

🌸 DSN OPTIONS 🌸

These DSN options are used to create a DSN. Each one is given like "option=value". They're case-sensitive, so P and p are absolutely not the same option, bestie. There can't be any whitespace before or after the "=", and if the value contains whitespace it has to be quoted. DSN options are comma-separated. See the percona-toolkit manpage for the full tea. ☕

  • 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 the 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.
  • s — dsn: mysql_ssl; copy: yes — Create SSL connection.

🦋 ENVIRONMENT 🦋

The environment variable "PTDEBUG" turns on verbose debugging output to STDERR. To enable debugging and capture all the output into a file, run the tool like this:

PTDEBUG=1 pt-replica-restart ... > FILE 2>&1
⚠️ Be careful, okay? The debugging output is voluminous and can generate several megabytes of output. Like, megabytes. 🔥

💀 ATTENTION 💀

Using <PTDEBUG> might expose passwords. When debug is enabled, all command line parameters are shown in the output. So yeah, mind who's reading that file. 🙈

🎀 SYSTEM REQUIREMENTS 🎀

You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl. That's the whole bar. 💅

🐛 BUGS 🐛

For a list of known bugs, see <https://jira.percona.com/projects/PT/issues>.

Please report bugs at <https://jira.percona.com/projects/PT>. Drop the following info into your bug report, please and thank you 🫶:

  • 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 you can, include debugging output by running the tool with "PTDEBUG" — see "ENVIRONMENT".

🌈 DOWNLOADING 🌈

Visit <http://www.percona.com/software/percona-toolkit/> to download the latest release of Percona Toolkit. Or, grab the latest release straight from the command line:

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

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

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

You can also get individual tools from the latest release:

wget percona.com/get/TOOL

Replace "TOOL" with the name of any tool. Slay. ✨

👑 AUTHORS 👑

Baron Schwartz

🧚 ABOUT PERCONA TOOLKIT 🧚

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 <http://www.percona.com/software/> to learn about other free, open-source software from Percona. 💖

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.

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.

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-replica-restart 3.7.1-4

😭 POD ERRORS 😭

Hey! The above document had some coding errors, which are explained below:

Around line 6308:

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

And that's a wrap, bestie 🫶💜 This little saga was rendered by perl v5.42.2 and dated 2026-09-01 — classic PT-SLAVE-RESTART(1) behavior, honestly. Go restart some replicas, you've got this. ✨🎀

📦 where this page comes from