PT-HEARTBEAT(1)

NAME
pt-heartbeat - Monitor MySQL replication delay.

SYNOPSIS
Usage: pt-heartbeat [OPTIONS] [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
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-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.

Percona XtraDB Cluster
Although pt-heartbeat should work with all supported versions of Percona XtraDB Cluster (PXC), we recommend using 5.5.28-23.7 and newer.

If you are setting up heartbeat instances between cluster nodes, keep in mind that, since the speed of the cluster is determined by its slowest node, pt-heartbeat will not report how fast the cluster itself is, but only how fast events are replicating from one node to another.

You must specify "--master-server-id" for "--monitor" and "--check" instances.

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.

--check-read-only
    Check if the server has read_only enabled; If it does, the tool skips doing any inserts.

--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);

    or if using "--utc":

      INSERT INTO heartbeat (ts, server_id) VALUES (UTC_TIMESTAMP(), 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());

    or if using "--utc":

      INSERT INTO heartbeat (id, ts) VALUES (1, UTC_TIMESTAMP());

    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. 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.

--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: 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-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: 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.

--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.

--utc
    Ignore system time zones and use only UTC. By default pt-heartbeat does not check or adjust for different system or MySQL time zones which can cause the tool to compute the lag incorrectly. Specifying this option is a good idea because it ensures that the tool works correctly regardless of time zones.

    If used, this option must be used for all pt-heartbeat instances: "--update", "--monitor", "--check", etc. You should probably set the option in a "--config" file. Mixing this option with pt-heartbeat instances not using this option will cause false-positive lag readings due to different time zones (unless all your systems are set to use UTC, in which case this option isn't required).

--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 <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-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:

•   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/ <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 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 2007-2013 Percona Ireland Ltd, 2006 Proven Scaling LLC and Six Apart Ltd.

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 2.2.4