PT-HEARTBEAT(1p) User Contributed Perl Documentation PT-HEARTBEAT(1p)
NAME
pt-heartbeat - Monitor MySQL replication delay.
SYNOPSIS
Usage: pt-heartbeat [OPTION...] [DSN] --update|--monitor|--check|--stop
pt-heartbeat measures replication lag on a MySQL or PostgreSQL server. You can use it to update a master or monitor a replica. If
possible, MySQL connection options are read from your .my.cnf file.
Start daemonized process to update test.heartbeat table on master:
pt-heartbeat -D test --update -h master-server --daemonize
Monitor replication lag on slave:
pt-heartbeat -D test --monitor -h slave-server
pt-heartbeat -D test --monitor -h slave-server --dbi-driver Pg
Check slave lag once and exit (using optional DSN to specify slave host):
pt-heartbeat -D test --check h=slave-server
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-heartbeat merely reads and writes a single record in a table. It should be very low-risk.
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-heartbeat <http://www.percona.com/bugs/pt-
heartbeat>.
See also "BUGS" for more information on filing bugs and getting help.
DESCRIPTION
pt-heartbeat is a two-part MySQL and PostgreSQL replication delay monitoring system that measures delay by looking at actual replicated
data. This avoids reliance on the replication mechanism itself, which is unreliable. (For example, "SHOW SLAVE STATUS" on MySQL).
The first part is an "--update" instance of pt-heartbeat that connects to a master and updates a timestamp ("heartbeat record") every
"--interval" seconds. Since the heartbeat table may contain records from multiple masters (see "MULTI-SLAVE HIERARCHY"), the server's ID
(@@server_id) is used to identify records.
The second part is a "--monitor" or "--check" instance of pt-heartbeat that connects to a slave, examines the replicated heartbeat record
from its immediate master or the specified "--master-server-id", and computes the difference from the current system time. If replication
between the slave and the master is delayed or broken, the computed difference will be greater than zero and potentially increase if
"--monitor" is specified.
You must either manually create the heartbeat table on the master or use "--create-table". See "--create-table" for the proper heartbeat
table structure. The "MEMORY" storage engine is suggested, but not required of course, for MySQL.
The heartbeat table must contain a heartbeat row. By default, a heartbeat row is inserted if it doesn't exist. This feature can be
disabled with the "--[no]insert-heartbeat-row" option in case the database user does not have INSERT privileges.
pt-heartbeat depends only on the heartbeat record being replicated to the slave, so it works regardless of the replication mechanism
(built-in replication, a system such as Continuent Tungsten, etc). It works at any depth in the replication hierarchy; for example, it
will reliably report how far a slave lags its master's master's master. And if replication is stopped, it will continue to work and report
(accurately!) that the slave is falling further and further behind the master.
pt-heartbeat has a maximum resolution of 0.01 second. The clocks on the master and slave servers must be closely synchronized via NTP. By
default, "--update" checks happen on the edge of the second (e.g. 00:01) and "--monitor" checks happen halfway between seconds (e.g.
00:01.5). As long as the servers' clocks are closely synchronized and replication events are propagating in less than half a second, pt-
heartbeat will report zero seconds of delay.
pt-heartbeat will try to reconnect if the connection has an error, but will not retry if it can't get a connection when it first starts.
The "--dbi-driver" option lets you use pt-heartbeat to monitor PostgreSQL as well. It is reported to work well with Slony-1 replication.
MULTI-SLAVE HIERARCHY
If the replication hierarchy has multiple slaves which are masters of other slaves, like "master -> slave1 -> slave2", "--update" instances
can be ran on the slaves as well as the master. The default heartbeat table (see "--create-table") is keyed on the "server_id" column, so
each server will update the row where "server_id=@@server_id".
For "--monitor" and "--check", if "--master-server-id" is not specified, the tool tries to discover and use the slave's immediate master.
If this fails, or if you want monitor lag from another master, then you can specify the "--master-server-id" to use.
For example, if the replication hierarchy is "master -> slave1 -> slave2" with corresponding server IDs 1, 2 and 3, you can:
pt-heartbeat --daemonize -D test --update -h master
pt-heartbeat --daemonize -D test --update -h slave1
Then check (or monitor) the replication delay from master to slave2:
pt-heartbeat -D test --master-server-id 1 --check slave2
Or check the replication delay from slave1 to slave2:
pt-heartbeat -D test --master-server-id 2 --check slave2
Stopping the "--update" instance one slave1 will not affect the instance on master.
MASTER AND SLAVE STATUS
The default heartbeat table (see "--create-table") has columns for saving information from "SHOW MASTER STATUS" and "SHOW SLAVE STATUS".
These columns are optional. If any are present, their corresponding information will be saved.
OPTIONS
Specify at least one of "--stop", "--update", "--monitor", or "--check".
"--update", "--monitor", and "--check" are mutually exclusive.
"--daemonize" and "--check" are mutually exclusive.
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.
--check
Check slave delay once and exit. If you also specify "--recurse", the tool will try to discover slave's of the given slave and check
and print their lag, too. The hostname or IP and port for each slave is printed before its delay. "--recurse" only works with MySQL.
--config
type: Array
Read this comma-separated list of config files; if specified, this must be the first option on the command line.
--create-table
Create the heartbeat "--table" if it does not exist.
This option causes the table specified by "--database" and "--table" to be created with the following MAGIC_create_heartbeat table
definition:
CREATE TABLE heartbeat (
ts varchar(26) NOT NULL,
server_id int unsigned NOT NULL PRIMARY KEY,
file varchar(255) DEFAULT NULL, -- SHOW MASTER STATUS
position bigint unsigned DEFAULT NULL, -- SHOW MASTER STATUS
relay_master_log_file varchar(255) DEFAULT NULL, -- SHOW SLAVE STATUS
exec_master_log_pos bigint unsigned DEFAULT NULL -- SHOW SLAVE STATUS
);
The heartbeat table requires at least one row. If you manually create the heartbeat table, then you must insert a row by doing:
INSERT INTO heartbeat (ts, server_id) VALUES (NOW(), N);
where "N" is the server's ID; do not use @@server_id because it will replicate and slaves will insert their own server ID instead of
the master's server ID.
This is done automatically by "--create-table".
A legacy version of the heartbeat table is still supported:
CREATE TABLE heartbeat (
id int NOT NULL PRIMARY KEY,
ts datetime NOT NULL
);
Legacy tables do not support "--update" instances on each slave of a multi-slave hierarchy like "master -> slave1 -> slave2". To
manually insert the one required row into a legacy table:
INSERT INTO heartbeat (id, ts) VALUES (1, NOW());
The tool automatically detects if the heartbeat table is legacy.
See also "MULTI-SLAVE HIERARCHY".
--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.
--dbi-driver
default: mysql; type: string
Specify a driver for the connection; "mysql" and "Pg" are supported.
--defaults-file
short form: -F; type: string
Only read mysql options from the given file. You must give an absolute pathname.
--file
type: string
Print latest "--monitor" output to this file.
When "--monitor" is given, prints output to the specified file instead of to STDOUT. The file is opened, truncated, and closed every
interval, so it will only contain the most recent statistics. Useful when "--daemonize" is given.
--frames
type: string; default: 1m,5m,15m
Timeframes for averages.
Specifies the timeframes over which to calculate moving averages when "--monitor" is given. Specify as a comma-separated list of
numbers with suffixes. The suffix can be s for seconds, m for minutes, h for hours, or d for days. The size of the largest frame
determines the maximum memory usage, as up to the specified number of per-second samples are kept in memory to calculate the averages.
You can specify as many timeframes as you like.
--help
Show help and exit.
--host
short form: -h; type: string
Connect to host.
--[no]insert-heartbeat-row
default: yes
Insert a heartbeat row in the "--table" if one doesn't exist.
The heartbeat "--table" requires a heartbeat row, else there's nothing to "--update", "--monitor", or "--check"! By default, the tool
will insert a heartbeat row if one is not already present. You can disable this feature by specifying "--no-insert-heartbeat-row" in
case the database user does not have INSERT privileges.
--interval
type: float; default: 1.0
How often to update or check the heartbeat "--table". Updates and checks begin on the first whole second then repeat every
"--interval" seconds for "--update" and every "--interval" plus "--skew" seconds for "--monitor".
For example, if at 00:00.4 an "--update" instance is started at 0.5 second intervals, the first update happens at 00:01.0, the next at
00:01.5, etc. If at 00:10.7 a "--monitor" instance is started at 0.05 second intervals with the default 0.5 second "--skew", then the
first check happens at 00:11.5 (00:11.0 + 0.5) which will be "--skew" seconds after the last update which, because the instances are
checking at synchronized intervals, happened at 00:11.0.
The tool waits for and begins on the first whole second just to make the interval calculations simpler. Therefore, the tool could wait
up to 1 second before updating or checking.
The minimum (fastest) interval is 0.01, and the maximum precision is two decimal places, so 0.015 will be rounded to 0.02.
If a legacy heartbeat table (see "--create-table") is used, then the maximum precision is 1s because the "ts" column is type
"datetime".
--log
type: string
Print all output to this file when daemonized.
--master-server-id
type: string
Calculate delay from this master server ID for "--monitor" or "--check". If not given, pt-heartbeat attempts to connect to the
server's master and determine its server id.
--monitor
Monitor slave delay continuously.
Specifies that pt-heartbeat should check the slave's delay every second and report to STDOUT (or if "--file" is given, to the file
instead). The output is the current delay followed by moving averages over the timeframe given in "--frames". For example,
5s [ 0.25s, 0.05s, 0.02s ]
--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.
--print-master-server-id
Print the auto-detected or given "--master-server-id". If "--check" or "--monitor" is specified, specifying this option will print the
auto-detected or given "--master-server-id" at the end of each line.
--recurse
type: int
Check slaves recursively to this depth in "--check" mode.
Try to discover slave servers recursively, to the specified depth. After discovering servers, run the check on each one of them and
print the hostname (if possible), followed by the slave delay.
This currently works only with MySQL. See "--recursion-method".
--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-heartbeat 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.
--replace
Use "REPLACE" instead of "UPDATE" for --update.
When running in "--update" mode, use "REPLACE" instead of "UPDATE" to set the heartbeat table's timestamp. The "REPLACE" statement is
a MySQL extension to SQL. This option is useful when you don't know whether the table contains any rows or not. It must be used in
conjunction with --update.
--run-time
type: time
Time to run before exiting.
--sentinel
type: string; default: /tmp/pt-heartbeat-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.
--skew
type: float; default: 0.5
How long to delay checks.
The default is to delay checks one half second. Since the update happens as soon as possible after the beginning of the second on the
master, this allows one half second of replication delay before reporting that the slave lags the master by one second. If your clocks
are not completely accurate or there is some other reason you'd like to delay the slave more or less, you can tweak this value. Try
setting the "PTDEBUG" environment variable to see the effect this has.
--socket
short form: -S; type: string
Socket file to use for connection.
--stop
Stop running instances by creating the sentinel file.
This should have the effect of stopping all running instances which are watching the same sentinel file. If none of "--update",
"--monitor" or "--check" is specified, "pt-heartbeat" will exit after creating the file. If one of these is specified, "pt-heartbeat"
will wait the interval given by "--interval", 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-heartbeat" 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-heartbeat --update -D test --stop
--sentinel /tmp/pt-heartbeat-hourly
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".
--table
type: string; default: heartbeat
The table to use for the heartbeat.
Don't specify database.table; use "--database" to specify the database.
See "--create-table".
--update
Update a master's heartbeat.
--user
short form: -u; type: string
User for login if not current user.
--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-heartbeat ... > 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-heartbeat <http://www.percona.com/bugs/pt-heartbeat>.
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
Proven Scaling LLC, SixApart Ltd, Baron Schwartz, and Daniel Nichter
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 2006 Proven Scaling LLC and Six Apart Ltd, 2007-2012 Percona Inc. Feedback and improvements are welcome.
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-heartbeat 2.1.2
perl v5.14.2 2012-06-15 PT-HEARTBEAT(1p)