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Manual Reference Pages  -  PT-FK-ERROR-LOGGER (1)

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pt-fk-error-logger - Log MySQL foreign key errors.



Usage: pt-fk-error-logger [OPTIONS] [DSN]

pt-fk-error-logger logs information about foreign key errors on the given DSN. Information is printed to STDOUT, and it can also be saved to a table by specifying --dest. The tool runs for forever unless --run-time or --iterations is specified.

Print foreign key errors on host1:

   pt-fk-error-logger h=host1

Print foreign key errors on host1 once then exit:

   pt-fk-error-logger h=host1 --iterations 1

Save foreign key errors on host1 to percona_schema.fke on host2:

  pt-fk-error-logger h=host1 --dest h=host2,D=percona_schema,t=fke


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


pt-fk-error-logger prints or saves the foreign key errors text from SHOW INNODB STATUS. The errors are not parsed or interpreted in any way. Foreign key errors are uniquely identified by their timestamp. Only new (more recent) errors are printed or saved.

By default the tool runs forever, checking every --interval seconds for new foreign key errors. Specify --run-time and/or --iterations to limit how long the tool runs.


The foreign key error text from SHOW ENGINE INNODB STATUS is printed to STDOUT, unless --quiet is specified. Errors and warnings are printed to STDERR.


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.

--config type: Array

Read this comma-separated list of config files; if specified, this must be the first option on the command line.

--daemonize Fork to the background and detach from the shell. POSIX operating systems only.
--database short form: -D; type: string

Connect to this database.

--defaults-file short form: -F; type: string

Only read mysql options from the given file. You must give an absolute pathname.

--dest type: DSN

Save foreign key errors in this table. The DSN must specify a database (D) and table (t).

Missing DSN values are inherited from the DSN being monitored, so you can omit most values if you’re saving foreign key errors on the same host.

The following table is suggested:

 CREATE TABLE foreign_key_errors (
   ts datetime NOT NULL,
   error text NOT NULL,

The only information saved is the timestamp and the foreign key error text.

--help Show help and exit.
--host short form: -h; type: string

Connect to host.

--interval type: time; default: 30

How often to check for foreign key errors.

--iterations type: int

How many times to check for foreign key errors. By default, this option is undefined which means an infinite number of iterations. The tool always exits for --run-time, regardless of the value specified for this option. For example, the tool will exit after 1 minute with --run-time 1m --iterations 4 --interval 30 because 4 iterations at 30 second intervals would take 2 minutes, longer than the 1 mintue run-time.

--log type: string

Print all output to this file when daemonized.

--password short form: -p; type: string

Password to use when connecting.

--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.

--quiet Do not print foreign key errors; only print errors and warnings to STDERR.
--run-time type: time

How long to run before exiting. By default, the tool runs forever.

--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.

--socket short form: -S; type: string

Socket file to use for connection.

--user short form: -u; type: string

User for login if not current user.

--version Show version and exit.
--[no]version-check default: yes

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 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 tool’s normal output. This feature should never interfere with the normal operation of the tool.

For more information, visit <>.


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.
o A

dsn: charset; copy: yes

Default character set.

o D

dsn: database; copy: yes

Default database.

o F

dsn: mysql_read_default_file; copy: yes

Only read default options from the given file

o h

dsn: host; copy: yes

Connect to host.

o p

dsn: password; copy: yes

Password to use when connecting.

o P

dsn: port; copy: yes

Port number to use for connection.

o S

dsn: mysql_socket; copy: yes

Socket file to use for connection.

o t

Table in which to store foreign key errors.

o u

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-fk-error-logger ... > 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 <>.

Please report bugs at <>. Include the following information in your bug report:
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.)
If possible, include debugging output by running the tool with PTDEBUG; see ENVIRONMENT.


Visit <> to download the latest release of Percona Toolkit. Or, get the latest release from the command line:




You can also get individual tools from the latest release:


Replace TOOL with the name of any tool.


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 <> to learn about other free, open-source software from Percona.


This program is copyright 2011-2015 Percona LLC and/or its affiliates.


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-fk-error-logger 2.2.14
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