PT-SLAVE-RESTART(1p) User Contributed Perl Documentation PT-SLAVE-RESTART(1p)
NAME
pt-slave-restart - Watch and restart MySQL replication after errors.
SYNOPSIS
Usage: pt-slave-restart [OPTION...] [DSN]
pt-slave-restart watches one or more MySQL replication slaves for errors, and tries to restart replication if it stops.
RISKS
The following section is included to inform users about the potential risks, whether known or unknown, of using this tool. The two main
categories of risks are those created by the nature of the tool (e.g. read-only tools vs. read-write tools) and those created by bugs.
pt-slave-restart is a brute-force way to try to keep a slave server running when it is having problems with replication. Don't be too
hasty to use it unless you need to. If you use this tool carelessly, you might miss the chance to really solve the slave server's
problems.
At the time of this release there is a bug that causes an invalid "CHANGE MASTER TO" statement to be executed.
The authoritative source for updated information is always the online issue tracking system. Issues that affect this tool will be marked
as such. You can see a list of such issues at the following URL: http://www.percona.com/bugs/pt-slave-restart
<http://www.percona.com/bugs/pt-slave-restart>.
See also "BUGS" for more information on filing bugs and getting help.
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.
Note: it has come to my attention that Yahoo! had or has an internal tool called fix_repl, described to me by a past Yahoo! employee and
mentioned in the first edition of High Performance MySQL. Apparently this tool does the same thing. Make no mistake, though: this is not
a way to "fix replication." In fact I would not even encourage its use on a regular basis; I use it only when I have an error I know I
just need to skip past.
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.
o The initial sleep time is given by "--sleep".
o If it checks and finds an error, it halves the previous sleep time.
o If it finds no error, it doubles the previous sleep time.
o The sleep time is bounded below by "--min-sleep" and above by "--max-sleep".
o 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.
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 when daemonized. The file contains the process ID of the daemonized instance. The PID file is removed when
the daemonized instance exits. The program checks for the existence of the PID file when starting; if it exists and the process with
the matching PID exists, the program 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: string
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: string; default: wait_timeout=10000
Set these MySQL variables. Immediately after connecting to MySQL, this string will be appended to SET and executed.
--skip-count
type: int; default: 1
Number of statements to skip when restarting the slave.
--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.
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.
o A
dsn: charset; copy: yes
Default character set.
o D
dsn: database; copy: yes
Default database.
o F
dsn: mysql_read_default_file; copy: yes
Only read default options from the given file
o h
dsn: host; copy: yes
Connect to host.
o p
dsn: password; copy: yes
Password to use when connecting.
o P
dsn: port; copy: yes
Port number to use for connection.
o S
dsn: mysql_socket; copy: yes
Socket file to use for connection.
o 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 <http://www.percona.com/bugs/pt-slave-restart>.
Please report bugs at https://bugs.launchpad.net/percona-toolkit <https://bugs.launchpad.net/percona-toolkit>. Include the following
information in your bug report:
o Complete command-line used to run the tool
o Tool "--version"
o MySQL version of all servers involved
o Output from the tool including STDERR
o 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/ <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 developed by Percona for MySQL support and consulting.
Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and
developed primarily by him and Daniel Nichter, both of whom are employed by Percona. Visit <http://www.percona.com/software/> for more
software developed by Percona.
COPYRIGHT, LICENSE, AND WARRANTY
This program is copyright 2007-2011 Baron Schwartz, 2011-2012 Percona Inc. Feedback and improvements are welcome.
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 2.1.2
perl v5.14.2 2012-06-15 PT-SLAVE-RESTART(1p)