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.
- •
- 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
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