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percona-toolkit/docs/user/source/pt-slave-delay.rst
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.. program:: pt-slave-delay
===========================
:program:`pt-slave-delay`
===========================
.. highlight:: perl
NAME
====
:program:`pt-slave-delay` - Make a |MySQL| slave server lag behind its master.
SYNOPSIS
========
Usage
-----
::
pt-slave-delay [OPTION...] SLAVE-HOST [MASTER-HOST]
:program:`pt-slave-delay` starts and stops a slave server as needed to make it lag
behind the master. The SLAVE-HOST and MASTER-HOST use DSN syntax, and
values are copied from the SLAVE-HOST to the MASTER-HOST if omitted.
To hold slavehost one minute behind its master for ten minutes:
.. code-block:: perl
pt-slave-delay --delay 1m --interval 15s --run-time 10m slavehost
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.
:program:`pt-slave-delay` is generally very low-risk. It simply starts and stops the
replication SQL thread. This might cause monitoring systems to think the slave
is having trouble.
At the time of this release, we know of no bugs that could cause serious harm to
users.
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-delay <http://www.percona.com/bugs/pt-slave-delay>`_.
See also :ref:`bugs` for more information on filing bugs and getting help.
DESCRIPTION
===========
:program:`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
:option:`--delay` and :option:`--delay` + :option:`--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, :program:`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, :program:`pt-slave-delay` will automatically connect to the
master to find binary log positions. If :option:`--ask-pass` and :option:`--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
:option:`--use-master` explicitly when daemonizing, or don't specify :option:`--ask-pass`.
The SLAVE-HOST and optional MASTER-HOST are both DSNs. See "DSN OPTIONS".
Missing MASTER-HOST values are filled in with values from SLAVE-HOST, so you
don't need to specify them in both places. :program:`pt-slave-delay` reads all normal
|MySQL| option files, such as :file:`~/.my.cnf`, so you may not need to specify username, password and other common options at all.
:program:`pt-slave-delay` tries to exit gracefully by trapping signals such as ``Ctrl-C``.
You cannot bypass :option:`--[no]continue` with a trappable signal.
PRIVILEGES
==========
:program:`pt-slave-delay` requires the following privileges: ``PROCESS``, ``REPLICATION CLIENT``, and ``SUPER``.
OUTPUT
======
If you specify :option:`--quiet`, there is no output. Otherwise, the normal output
is a status message consisting of a timestamp and information about what
:program:`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.
.. option:: --ask-pass
Prompt for a password when connecting to |MySQL|.
.. option:: --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|.
.. option:: --config
type: Array
Read this comma-separated list of config files; if specified, this must be the
first option on the command line.
.. option:: --[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
:program:`pt-slave-delay` with ``Control-C``.
.. option:: --daemonize
Fork to the background and detach from the shell. POSIX
operating systems only.
.. option:: --defaults-file
short form: -F; type: string
Only read mysql options from the given file. You must give an absolute
pathname.
.. option:: --delay
type: time; default: 1h
How far the slave should lag its master.
.. option:: --help
Show help and exit.
.. option:: --host
short form: -h; type: string
Connect to host.
.. option:: --interval
type: time; default: 1m
How frequently :program:`pt-slave-delay` should check whether the slave needs to be
started or stopped.
.. option:: --log
type: string
Print all output to this file when daemonized.
.. option:: --password
short form: -p; type: string
Password to use when connecting.
.. option:: --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.
.. option:: --port
short form: -P; type: int
Port number to use for connection.
.. option:: --quiet
short form: -q
Don't print informational messages about operation. See OUTPUT for details.
.. option:: --run-time
type: time
How long :program:`pt-slave-delay` should run before exiting. The default is to run
forever.
.. option:: --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.
.. option:: --socket
short form: -S; type: string
Socket file to use for connection.
.. option:: --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-HOST on the command
line, :program:`pt-slave-delay` examines the slave's SHOW SLAVE STATUS to determine the
hostname and port for connecting to the master.
:program:`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-HOST option
explicitly on the command line.
.. option:: --user
short form: -u; type: string
User for login if not current user.
.. option:: --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.
* ``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:
.. code-block:: perl
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 <http://www.percona.com/bugs/pt-slave-delay>`_.
Please report bugs at `https://bugs.launchpad.net/percona-toolkit <https://bugs.launchpad.net/percona-toolkit>`_.
AUTHORS
=======
*Sergey Zhuravlev* and *Baron Schwartz*
COPYRIGHT, LICENSE, AND WARRANTY
================================
This program is copyright 2007-2011 Sergey Zhuravle and *Baron Schwartz*,
2011 Percona Inc.
Feedback and improvements are welcome.
VERSION
=======
:program:`pt-slave-delay` 1.0.1
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