Provided by: percona-toolkit_3.2.1-1_all 
NAME
pt-slave-restart - Watch and restart MySQL replication after errors.
SYNOPSIS
Usage: pt-slave-restart [OPTIONS] [DSN]
pt-slave-restart watches one or more MySQL replication slaves 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-slave-restart watches one or more MySQL replication slaves and tries to skip statements that cause
errors. It polls slaves intelligently with an exponentially varying sleep time. You can specify errors
to skip and run the slaves until a certain binlog position.
Although this tool can help a slave advance past errors, you should not rely on it to "fix" replication.
If slave errors occur frequently or unexpectedly, you should identify and fix the root cause.
OUTPUT
pt-slave-restart prints a line every time it sees the slave 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-slave-restart sleeps intelligently between polling the slave. 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-slave-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-slave-restart supports Global Transaction IDs introduced in MySQL 5.6.5.
It's important to keep in mind that:
• pt-slave-restart will not skip transactions when multiple replication threads are being used
(slave_parallel_workers > 0). pt-slave-restart does not know what the GTID event is of the failed
transaction of a specific slave thread.
• The default behavior is to skip the next transaction from the slave's master. Writes can originate
on different servers, each with their own UUID.
See "--master-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-slave-restart should work on many versions of MySQL. Lettercase of many output columns from SHOW
SLAVE 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 slaves even when there is no error. With this option enabled, pt-slave-restart will not let
you stop the slave manually if you want to!
--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.
--[no]check-relay-log
default: yes
Check the last relay log file and position before checking for slave errors.
By default pt-slave-restart will not doing 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 slave 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-slave-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 SLAVE 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-slave-restart will try to restart the
slave. If it exists but doesn't match, pt-slave-restart will exit.
The error text is in the "last_error" column of "SHOW SLAVE 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.
--max-sleep
type: float; default: 64
Maximum sleep seconds.
The maximum time pt-slave-restart will sleep before polling the slave again. This is also the time
that pt-slave-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-slave-restart will sleep before polling the slave again. See "SLEEP".
--monitor
Whether to monitor the slave (default). Unless you specify --monitor explicitly, "--stop" will
disable it.
--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 slaves of the specified server, up to the specified number of servers deep in the hierarchy.
The default depth of 0 means "just watch the slave specified."
pt-slave-restart examines "SHOW PROCESSLIST" and tries to determine which connections are from
slaves, then connect to them. See "--recursion-method".
Recursion works by finding all slaves when the program starts, then watching them. If there is more
than one slave, "pt-slave-restart" uses "fork()" to monitor them.
This also works if you have configured your slaves to show up in "SHOW SLAVE HOSTS". 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 slaves.
Possible methods are:
METHOD USES
=========== ==================
processlist SHOW PROCESSLIST
hosts SHOW SLAVE HOSTS
none Do not find slaves
The processlist method is preferred because SHOW SLAVE HOSTS is not reliable. However, the hosts
method is required if the server uses a non-standard port (not 3306). Usually pt-slave-restart does
the right thing and finds the slaves, but you may give a preferred method and it will be used first.
If it doesn't find any slaves, the other methods will be tried.
--run-time
type: time
Time to run before exiting. Causes pt-slave-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-slave-restart-sentinel
Exit if this file exists.
--slave-user
type: string
Sets the user to be used to connect to the slaves. This parameter allows you to have a different
user with less privileges on the slaves but that user must exist on all slaves.
--slave-password
type: string
Sets the password to be used to connect to the slaves. It can be used with --slave-user and the
password for the user must be the same on all slaves.
--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.
--skip-count
type: int; default: 1
Number of statements to skip when restarting the slave.
--master-uuid
type: string
When using GTID, an empty transaction should be created in order to skip it. If writes are coming
from different nodes in the replication tree above, it is not possible to know which event from which
UUID to skip.
By default, transactions from the slave's master ('Master_UUID' from "SHOW SLAVE STATUS") are
skipped.
For example, with
master1 -> slave1 -> slave2
When skipping events on slave2 that were written to master1, you must specify the UUID of master1,
else the tool will use the UUID of slave1 by default.
See "GLOBAL TRANSACTION IDS".
--sleep
type: int; default: 1
Initial sleep seconds between checking the slave.
See "SLEEP".
--socket
short form: -S; type: string
Socket file to use for connection.
--stop
Stop running instances by creating the sentinel file.
Causes "pt-slave-restart" to create the sentinel file specified by "--sentinel". This should have
the effect of stopping all running instances which are watching the same sentinel file. If
"--monitor" isn't specified, "pt-slave-restart" will exit after creating the file. If it is
specified, "pt-slave-restart" will wait the interval given by "--max-sleep", then remove the file and
continue working.
You might find this handy to stop cron jobs gracefully if necessary, or to replace one running
instance with another. For example, if you want to stop and restart "pt-slave-restart" every hour
(just to make sure that it is restarted every hour, in case of a server crash or some other problem),
you could use a "crontab" line like this:
0 * * * * pt-slave-restart --monitor --stop --sentinel /tmp/pt-slave-restartup
The non-default "--sentinel" will make sure the hourly "cron" job stops only instances previously
started with the same options (that is, from the same "cron" job).
See also "--sentinel".
--until-master
type: string
Run until this master log file and position. Start the slave, and retry if it fails, until it
reaches the given replication coordinates. The coordinates are the logfile and position on the
master, given by relay_master_log_file, exec_master_log_pos. The argument must be in the format
"file,pos". Separate the filename and position with a single comma and no space.
This will also cause an UNTIL clause to be given to START SLAVE.
After reaching this point, the slave should be stopped and pt-slave-restart will exit.
--until-relay
type: string
Run until this relay log file and position. Like "--until-master", but in the slave's relay logs
instead. The coordinates are given by relay_log_file, relay_log_pos.
--user
short form: -u; type: string
User for login if not current user.
--verbose
short form: -v; cumulative: yes; default: 1
Adds more information to the output. This flag can be specified multiple times. e.g. -v -v OR -vv.
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 each time pt-slave-restart sleeps. To suppress all output use
the "--quiet" option.
--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>.
Show version and exit.
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-restart ... > 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.
BUGS
For a list of known bugs, see <http://www.percona.com/bugs/pt-slave-restart>.
Please report bugs at <https://jira.percona.com/projects/PT>. 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".
DOWNLOADING
Visit <http://www.percona.com/software/percona-toolkit/> to download the latest release of Percona
Toolkit. Or, get the latest release 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.
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.
COPYRIGHT, LICENSE, AND WARRANTY
This program is copyright 2011-2018 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 along with this program; if not, write
to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
VERSION
pt-slave-restart 3.2.1
POD ERRORS
Hey! The above document had some coding errors, which are explained below:
Around line 5994:
Non-ASCII character seen before =encoding in 'Percona’s'. Assuming UTF-8
perl v5.30.3 2020-08-30 PT-SLAVE-RESTART(1p)