NAME¶
pt-slave-delay - Make a MySQL slave server lag behind its master.
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:
- •
- 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-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.
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.
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".
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.
"pt-slave-delay" tries to exit gracefully by trapping signals such as
Ctrl-C. You cannot bypass "--[no]continue" with a trappable signal.
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.
- --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.
- --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 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>.
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-delay ... > 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-delay>.
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¶
Sergey Zhuravlev and Baron Schwartz
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
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.
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-delay 2.2.11