| PT-HEARTBEAT(1p) | User Contributed Perl Documentation | PT-HEARTBEAT(1p) |
pt-heartbeat - Monitor MySQL replication delay.
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
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:
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.
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.
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.
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.
Read this comma-separated list of config files; if specified, this must be the first option on the command line.
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".
Sets the engine to be used for the heartbeat table. The default storage engine is InnoDB as of MySQL 5.5.5.
The database to use for the connection.
Specify a driver for the connection; "mysql" and "Pg" are supported.
Only read mysql options from the given file. You must give an absolute pathname.
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.
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.
Connect to host.
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.
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".
Print all output to this file when daemonized.
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.
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 ]
If specified, pt-heartbeat will fail after given number of successive DBI errors (failure to connect to server or issue a query).
Password to use when connecting. If password contains commas they must be escaped with a backslash: "exam\,ple"
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 number to use for connection.
When "--check-read-only" is specified, the interval to sleep while the server is found to be read-only. If unspecified, "--interval" is used.
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".
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.
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.
Time to run before exiting.
Exit if this file exists.
Sets the user to be used to connect to the slaves. This parameter allows you to have a different user with less privileges on the slaves but that user must exist on all slaves.
Sets the password to be used to connect to the slaves. It can be used with --slave-user and the password for the user must be the same on all slaves.
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.
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 file to use for connection.
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".
The table to use for the heartbeat.
Don't specify database.table; use "--database" to specify the database.
See "--create-table".
User for login if not current user.
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).
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 its own version and also the versions of the following software: operating system, Percona Monitoring and Management (PMM), MySQL, Perl, MySQL driver for Perl (DBD::mysql), and Percona Toolkit. 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.
A secure connection to Percona’s Version Check database server is done to perform these checks. Each request is logged by the server, including software version numbers and unique ID of the checked system. The ID is generated by the Percona Toolkit installation script or when the Version Check database call is done for the first time.
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/doc/percona-toolkit/LATEST/version-check.html>.
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
Default database.
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. If password contains commas they must be escaped with a backslash: "exam\,ple"
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
User for login if not current user.
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://jira.percona.com/projects/PT>. Include the following information in your bug report:
If possible, include debugging output by running the tool with "PTDEBUG"; see "ENVIRONMENT".
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:
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.
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 2007-2018 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.
pt-heartbeat 3.2.1
Hey! The above document had some coding errors, which are explained below:
| 2020-08-30 | perl v5.30.3 |