pt-heartbeat¶

NAME¶

pt-heartbeat - Monitor MySQL replication delay.

SYNOPSIS¶

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 replication source 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 replication source:

pt-heartbeat -D test --update -h source-server --daemonize

Monitor replication lag on replica:

pt-heartbeat -D test --monitor -h replica-server

pt-heartbeat -D test --monitor -h replica-server --dbi-driver Pg

Check replica lag once and exit (using optional DSN to specify replica host):

pt-heartbeat -D test --check h=replica-server

RISKS¶

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:

Read the tool’s documentation
Review the tool’s known “BUGS”
Test the tool on a non-production server
Backup your production server and verify the backups

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 REPLICA STATUS on MySQL).

The first part is an --update instance of pt-heartbeat that connects to a replication source and updates a timestamp (“heartbeat record”) every --interval seconds. Since the heartbeat table may contain records from multiple replication sources (see “MULTI-REPLICA 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 replica, examines the replicated heartbeat record from its immediate source or the specified --source-server-id, and computes the difference from the current system time. If replication between the replica and the source 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 replication source 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 replica, 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 replica lags its source’s source’s source. And if replication is stopped, it will continue to work and report (accurately!) that the replica is falling further and further behind the source.

pt-heartbeat has a maximum resolution of 0.01 second. The clocks on the source and replica 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-REPLICA HIERARCHY¶

If the replication hierarchy has multiple replicas which are sources of other replicas, like “source -> replica1 -> replica2”, --update instances can be ran on the replicas as well as the source. 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 --source-server-id is not specified, the tool tries to discover and use the replica’s immediate source. If this fails, or if you want monitor lag from another source, then you can specify the --source-server-id to use.

For example, if the replication hierarchy is “source -> replica1 -> replica2” with corresponding server IDs 1, 2 and 3, you can:

pt-heartbeat --daemonize -D test --update -h source
pt-heartbeat --daemonize -D test --update -h replica1

Then check (or monitor) the replication delay from source to replica2:

pt-heartbeat -D test --source-server-id 1 --check replica2

Or check the replication delay from replica1 to replica2:

pt-heartbeat -D test --source-server-id 2 --check replica2

Stopping the --update instance one replica1 will not affect the instance on the source.

The default heartbeat table (see --create-table) has columns for saving information from SHOW BINARY LOG STATUS (SHOW MASTER STATUS before MySQL 8.4) and SHOW REPLICA STATUS. These columns are optional. If any are present, their corresponding information will be saved.

Percona XtraDB Cluster¶

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 --source-server-id for --monitor and --check instances.

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 replica delay once and exit. If you also specify --recurse, the tool will try to discover replica’s of the given replica and check and print their lag, too. The hostname or IP and port for each replica 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. See also --read-only-interval

--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 BINARY LOG STATUS
  position              bigint unsigned DEFAULT NULL, -- SHOW BINARY LOG STATUS
  relay_source_log_file varchar(255) DEFAULT NULL,    -- SHOW REPLICA STATUS
  exec_source_log_pos   bigint unsigned DEFAULT NULL  -- SHOW REPLICA 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 replicas will insert their own server ID instead of the source’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 replica of a multi-replica hierarchy like “source -> replica1 -> replica2”. 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-REPLICA HIERARCHY”.

--create-table-engine¶

type: string

Sets the engine to be used for the heartbeat table. The default storage engine is InnoDB as of MySQL 5.5.5.

--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

This option is deprecated and will be removed in future releases. Use --source-server-id instead.

--source-server-id¶

type: string

Calculate delay from this source server ID for --monitor or --check. If not given, pt-heartbeat attempts to connect to the server’s source and determine its server id.

--monitor¶

Monitor replica delay continuously.

Specifies that pt-heartbeat should check the replica’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 ]

--fail-successive-errors¶

type: int

If specified, pt-heartbeat will fail after given number of successive DBI errors (failure to connect to server or issue a query).

--password¶

short form: -p; type: string

Password to use when connecting. If password contains commas they must be escaped with a backslash: “exam,ple”

--pid¶

type: string

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¶

short form: -P; type: int

Port number to use for connection.

--print-master-server-id¶: This option is deprecated and will be removed in future releases. Use --print-source-server-id instead.

--print-source-server-id¶: Print the auto-detected or given --source-server-id. If --check or --monitor is specified, specifying this option will print the auto-detected or given --source-server-id at the end of each line.

--read-only-interval¶

type: int

When --check-read-only is specified, the interval to sleep while the server is found to be read-only. If unspecified, --interval is used.

--recurse¶

type: int

Check replicas recursively to this depth in --check mode.

Try to discover replica 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 replica delay.

This currently works only with MySQL. See --recursion-method.

--recursion-method¶

type: array; default: processlist,hosts

Preferred recursion method used to find replicas.

Possible methods are:

METHOD       USES
===========  ==================
processlist  SHOW PROCESSLIST
hosts        SHOW REPLICA HOSTS
none         Do not find replicas

The processlist method is preferred because SHOW REPLICA 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 replicas, but you may give a preferred method and it will be used first. If it doesn’t find any replicas, 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.

--slave-user¶

type: string

This option is deprecated and will be removed in future releases. Use --replica-user instead.

--slave-password¶

type: string

This option is deprecated and will be removed in future releases. Use --replica-password instead.

--replica-user¶

type: string

Sets the user to be used to connect to the replicas. This parameter allows you to have a different user with less privileges on the replicas but that user must exist on all replicas.

--replica-password¶

type: string

Sets the password to be used to connect to the replicas. It can be used with –replica-user and the password for the user must be the same on all replicas.

--set-vars¶

type: Array

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.

--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 replication source, this allows one half second of replication delay before reporting that the replica lags the source by one second. If your clocks are not completely accurate or there is some other reason you’d like to delay the replica 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 * * * * :program:`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).

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. If password contains commas they must be escaped with a backslash: “exam,ple”

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.

s

dsn: mysql_ssl; copy: yes

Create SSL connection

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.

ATTENTION¶

Using <PTDEBUG> might expose passwords. When debug is enabled, all command line parameters are shown in the 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 https://jira.percona.com/projects/PT/issues.

Please report bugs at https://jira.percona.com/projects/PT. 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/ 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

ABOUT PERCONA TOOLKIT¶

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.

COPYRIGHT, LICENSE, AND WARRANTY¶

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 3.6.0

pt-heartbeat¶

NAME¶

SYNOPSIS¶

Usage¶

RISKS¶

DESCRIPTION¶

MULTI-REPLICA HIERARCHY¶

Percona XtraDB Cluster¶

OPTIONS¶

DSN OPTIONS¶

ENVIRONMENT¶

ATTENTION¶

SYSTEM REQUIREMENTS¶

BUGS¶

DOWNLOADING¶

AUTHORS¶

ABOUT PERCONA TOOLKIT¶

COPYRIGHT, LICENSE, AND WARRANTY¶

VERSION¶

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