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mk-heartbeat

NAME

mk-heartbeat - Monitor MySQL replication delay.

SYNOPSIS

  mk-heartbeat -D test --update -h master-server
  mk-heartbeat -D test --monitor -h slave-server
  mk-heartbeat -D test --monitor -h slave-server --dbidriver Pg
 
 

DESCRIPTION

mk-heartbeat is a two-part MySQL and PostgreSQL replication delay monitoring system that doesn't require the slave to be working (in other words, it doesn't rely on "SHOW SLAVE STATUS" on MySQL). The first part updates a timestamp every second on the master. You must create a table on the master as follows:

  CREATE TABLE heartbeat (
    id int NOT NULL PRIMARY KEY,
    ts datetime NOT NULL
  );
  INSERT INTO heartbeat(id) VALUES(1);
 
 

The "MEMORY" storage engine is suggested, but not required of course, for MySQL.

Now you connect mk-heartbeat to the master and run it in ``--update'' mode to generate the heartbeat. This completes the first part.

The second part is to monitor the slave's delay with ``--monitor'' or ``--check''. This works even on daisy-chained slaves to any depth.

mk-heartbeat has a one-second resolution. It depends on the clocks on the master and slave servers being closely synchronized via NTP. ``--update'' checks happen on the edge of the second, and ``--monitor'' checks happen halfway between seconds. As long as the servers' clocks aren't skewed much and the replication events are propagating in less than half a second, mk-heartbeat will report zero seconds of delay.

mk-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 ``--dbidriver'' option lets you use mk-heartbeat to monitor PostgreSQL as well. It is reported to work well with Slony-1 replication.

DOWNLOADING

You can download Maatkit from Google Code at <http://code.google.com/p/maatkit/>, or you can get any of the tools easily with a command like the following:

    wget http://www.maatkit.org/get/toolname
    or
    wget http://www.maatkit.org/trunk/toolname
 
 

Where "toolname" can be replaced with the name (or fragment of a name) of any of the Maatkit tools. Once downloaded, they're ready to run; no installation is needed. The first URL gets the latest released version of the tool, and the second gets the latest trunk code from Subversion.

OPTIONS

Specify at least one of --stop, --update, --monitor, or --check.

--update, --monitor, and --check are mutually exclusive.

--daemonize and --check are mutually exclusive.

--askpass

Prompt for a password when connecting to MySQL.

--charset

short form: -A; type: string

Default character set.

Enables character set settings in Perl and MySQL. 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.

--daemonize

Fork to the background and detach from the shell. POSIX only.

--database

short form: -D; type: string

The database to use for the connection.

--dbidriver

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.

--host

short form: -h; type: string

Connect to host.

--interval

short form: -i; type: time; default: 1s

Interval between updates and checks.

How often to check or update values. The updates and checks will happen when the Unix time (seconds since epoch) is an even multiple of this value. The suffix is similar to ``--frames''.

--monitor

Monitor slave delay continuously.

Specifies that mk-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.

For example, '--daemonize --pid /tmp/mk-heartbeat.pid' would cause mk-heartbeat to create the PID file /tmp/mk-heartbeat.pid.

/var/run/ is usually not writable by non-root users, therefore /tmp/ is a more reliable alternative.

The PID file is removed when the daemonized instance of mk-heartbeat exits.

--port

short form: -P; type: int

Port number to use for connection.

--quiet

short form: -q

Suppresses normal output.

--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. It uses "SHOW PROCESSLIST" to discover slaves; if that returns nothing, it falls back to examining the output of "SHOW SLAVE HOSTS" to try to find slaves.

--replace

short form: -r

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.

--sentinel

type: string; default: /tmp/mk-heartbeat-sentinel

Exit if this file exists.

--setvars

type: string; default: wait_timeout=10000

Set these MySQL variables.

Specify any variables you want to be set immediately after connecting to MySQL. These will be included in a "SET" command.

--skew

short form: -k; type: int; default: 500000

How long to delay checks, in milliseconds.

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 "MKDEBUG" 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, "mk-heartbeat" will exit after creating the file. If one of these is specified, "mk-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 "mk-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 * * * * mk-heartbeat --update -D test --stop --sentinel /tmp/mk-heartbeatup
 
 

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

short form: -t; type: string; default: heartbeat

The table to use for the heartbeat.

Don't specify database.table; use ``--database'' to specify the database.

--time

short form: -m; type: time

Time to run before exiting.

--update

Update a master's heartbeat.

--user

short form: -u; type: string

User for login if not current user.

ENVIRONMENT

The environment variable "MKDEBUG" enables verbose debugging output in all of the Maatkit tools:

    MKDEBUG=1 mk-....
 
 

SYSTEM REQUIREMENTS

You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl.

SEE ALSO

See also mk-slave-delay and mk-slave-restart.

BUGS

Please use Google Code Issues and Groups to report bugs or request support: <http://code.google.com/p/maatkit/>.

Please include the complete command-line used to reproduce the problem you are seeing, the version of all MySQL servers involved, the complete output of the tool when run with ``--version'', and if possible, debugging output produced by running with the "MKDEBUG=1" environment variable.

COPYRIGHT, LICENSE AND WARRANTY

This program is copyright 2007-2008 Percona Inc. and copyright 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 MERCHANTIBILITY 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.

AUTHOR

Proven Scaling LLC, SixApart Ltd, and Baron Schwartz.

VERSION

This manual page documents Ver 1.0.12 Distrib 2725 $Revision: 2311 $.