PT-SLAVE-RESTART(1)

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
If you specify "--verbose", pt-slave-restart prints a line every time it sees the slave has an error. See "--verbose" for details.

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.

--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.

--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

    Be verbose; can specify multiple times. Verbosity 1 outputs connection information, a timestamp, relay_log_file, relay_log_pos, and last_errno. Verbosity 2 adds last_error. See also "--error-length". Verbosity 3 prints the current sleep time each time pt-slave-restart sleeps.

--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 the version of other programs on the local system in addition to its own version. For example, it checks the version of every MySQL server it connects to, Perl, and the Perl module DBD::mysql. 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.

    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/version-check>.

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.

•   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://bugs.launchpad.net/percona-toolkit>. 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 2011-2014 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 2.2.9