|o||Read the tools documentation|
|o||Review the tools known BUGS|
|o||Test the tool on a non-production server|
|o||Backup your production server and verify the backups|
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 servers 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 doesnt 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 masters masters 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.
The --dbi-driver option lets you use pt-heartbeat to monitor PostgreSQL as well. It is reported to work well with Slony-1 replication.
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 slaves 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:
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.
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.
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.
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 Perls 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 slaves 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 servers ID; do not use @@server_id because it will replicate and slaves will insert their own server ID instead of the masters 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 doesnt exist.
The heartbeat --table requires a heartbeat row, else theres 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 servers master and determine its server id.
--monitor Monitor slave delay continuously.
Specifies that pt-heartbeat should check the slaves 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 wont 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 doesnt 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 tables timestamp. The REPLACE statement is a MySQL extension to SQL. This option is useful when you dont 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:
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 youd 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.
Dont specify database.table; use --database to specify the database.
--update Update a masters heartbeat. --user short form: -u; type: string --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 isnt required).
--version Show version and exit. --[no]version-check default: yes
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 tools normal output. This feature should never interfere with the normal operation of the tool.
For more information, visit <https://www.percona.com/version-check>.
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.
dsn: charset; copy: yes
Default character set.
dsn: database; copy: yes
dsn: mysql_read_default_file; copy: yes
Only read default options from the given file
dsn: host; copy: yes
Connect to host.
dsn: password; copy: yes
Password to use when connecting.
dsn: port; copy: yes
Port number to use for connection.
dsn: mysql_socket; copy: yes
Socket file to use for connection.
dsn: user; copy: yes
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.
You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl.
For a list of known bugs, see <http://www.percona.com/bugs/pt-heartbeat>.
Please report bugs at <https://bugs.launchpad.net/percona-toolkit>. Include the following information in your bug report:
If possible, include debugging output by running the tool with PTDEBUG; see ENVIRONMENT.
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.)
Visit <http://www.percona.com/software/percona-toolkit/> to download the latest release of Percona Toolkit. Or, get the latest release from the command line:
Replace TOOL with the name of any tool.
Proven Scaling LLC, SixApart Ltd, Baron Schwartz, and Daniel Nichter
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.
This program is copyright 2007-2015 Percona LLC and/or its affiliates, 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.
|perl v5.20.3||PT-HEARTBEAT (1)||2015-04-10|