pt-slave-restartp - Online in the Cloud

PROGRAM:

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. 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.

--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. 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.

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