mk-heartbeat - Monitor MySQL replication delay.
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
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.
You can download Maatkit from the Sourceforge website at http://sourceforge.net/projects/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.
Specify at least one of --stop, --update, --monitor, or --check.
--update, --monitor, and --check are mutually exclusive.
--daemonize and --check are mutually exclusive.
Prompt for a password when connecting to MySQL.
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 slave delay once and exit.
Fork to the background and detach from the shell. POSIX only.
short form: -D; type: string
The database to use for the connection.
default: mysql; type: string
Specify a driver for the connection; mysql and Pg are supported.
short form: -F; type: string
Only read mysql options from the given file. You must give an absolute pathname.
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.
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.
short form: -h; type: string
Connect to host.
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 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 ]
short form: -p; type: string
Password to use when connecting.
short form: -P; type: int
Port number to use for connection.
short form: -q
Suppresses normal output.
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.
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.
type: string; default: /tmp/mk-heartbeat-sentinel
Exit if this file exists.
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.
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.
short form: -S; type: string
Socket file to use for connection.
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.
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.
short form: -m; type: time
Time to run before exiting.
Update a master's heartbeat.
short form: -u; type: string
User for login if not current user.
The environment variable MKDEBUG enables verbose debugging output in all of the
Maatkit tools:
MKDEBUG=1 mk-....
You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl.
See also the mk-slave-delay manpage and the mk-slave-restart manpage.
Please use the Sourceforge bug tracker, forums, and mailing lists to request support or report bugs: http://sourceforge.net/projects/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.
This program is copyright (c) 2006 Proven Scaling LLC and SixApart Ltd, and (c) 2007 Baron Schwartz. 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.
Proven Scaling LLC, SixApart Ltd, and Baron Schwartz.
This manual page documents Ver 1.0.9 Distrib 1972 $Revision: 1970 $.