pt-variable-advisor(1p)
NAME
pt-variable-advisor - Analyze MySQL variables and advise on possible problems.
SYNOPSIS
Usage: pt-variable-advisor [OPTIONS] [DSN]
pt-variable-advisor analyzes variables and advises on possible
problems.
Get SHOW VARIABLES from localhost:
pt-variable-advisor localhost
Get SHOW VARIABLES output saved in vars.txt:
pt-variable-advisor --source-of-variables vars.txt
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-variable-advisor examines "SHOW VARIABLES" for bad values and settings according to the "RULES" described below. It reports on variables that match the rules, so you can find bad settings in your MySQL server. At the time of this release, pt-variable-advisor only examples "SHOW VARIABLES", but other input sources are planned like "SHOW STATUS" and "SHOW SLAVE STATUS".
RULES
These are the rules that pt-variable-advisor will apply to SHOW
VARIABLES. Each rule has three parts: an ID, a severity, and a
description.
The rule's ID is a short, unique name for the rule. It usually relates
to the variable that the rule examines. If a variable is examined by
several rules, then the rules' IDs are numbered like "-1", "-2", "-N".
The rule's severity is an indication of how important it is that this
rule matched a query. We use NOTE, WARN, and CRIT to denote these
levels.
The rule's description is a textual, human-readable explanation of what
it means when a variable matches this rule. Depending on the verbosity
of the report you generate, you will see more of the text in the
description. By default, you'll see only the first sentence, which is
sort of a terse synopsis of the rule's meaning. At a higher verbosity,
you'll see subsequent sentences.
auto_increment
severity: note
Are you trying to write to more than one server in a dual-master or
ring replication configuration? This is potentially very dangerous
and in most cases is a serious mistake. Most people's reasons for
doing this are actually not valid at all.
concurrent_insert
severity: note
Holes (spaces left by deletes) in MyISAM tables might never be
reused.
connect_timeout
severity: note
A large value of this setting can create a denial of service
vulnerability.
debug
severity: crit
Servers built with debugging capability should not be used in
production because of the large performance impact.
delay_key_write
severity: warn
MyISAM index blocks are never flushed until necessary. If there is
a server crash, data corruption on MyISAM tables can be much worse
than usual.
flush
severity: warn
This option might decrease performance greatly.
flush_time
severity: warn
This option might decrease performance greatly.
have_bdb
severity: note
The BDB engine is deprecated. If you aren't using it, you should
disable it with the skip_bdb option.
init_connect
severity: note
The init_connect option is enabled on this server.
init_file
severity: note
The init_file option is enabled on this server.
init_slave
severity: note
The init_slave option is enabled on this server.
innodb_additional_mem_pool_size
severity: warn
This variable generally doesn't need to be larger than 20MB.
innodb_buffer_pool_size
severity: warn
The InnoDB buffer pool size is unconfigured. In a production
environment it should always be configured explicitly, and the
default 10MB size is not good.
innodb_checksums
severity: warn
InnoDB checksums are disabled. Your data is not protected from
hardware corruption or other errors!
innodb_doublewrite
severity: warn
InnoDB doublewrite is disabled. Unless you use a filesystem that
protects against partial page writes, your data is not safe!
innodb_fast_shutdown
severity: warn
InnoDB's shutdown behavior is not the default. This can lead to
poor performance, or the need to perform crash recovery upon
startup.
innodb_flush_log_at_trx_commit-1
severity: warn
InnoDB is not configured in strictly ACID mode. If there is a
crash, some transactions can be lost.
innodb_flush_log_at_trx_commit-2
severity: warn
Setting innodb_flush_log_at_trx_commit to 0 has no performance
benefits over setting it to 2, and more types of data loss are
possible. If you are trying to change it from 1 for performance
reasons, you should set it to 2 instead of 0.
innodb_force_recovery
severity: warn
InnoDB is in forced recovery mode! This should be used only
temporarily when recovering from data corruption or other bugs, not
for normal usage.
innodb_lock_wait_timeout
severity: warn
This option has an unusually long value, which can cause system
overload if locks are not being released.
innodb_log_buffer_size
severity: warn
The InnoDB log buffer size generally should not be set larger than
16MB. If you are doing large BLOB operations, InnoDB is not really
a good choice of engines anyway.
innodb_log_file_size
severity: warn
The InnoDB log file size is set to its default value, which is not
usable on production systems.
innodb_max_dirty_pages_pct
severity: note
The innodb_max_dirty_pages_pct is lower than the default. This can
cause overly aggressive flushing and add load to the I/O system.
flush_time
severity: warn
This setting is likely to cause very bad performance every
flush_time seconds.
key_buffer_size
severity: warn
The key buffer size is set to its default value, which is not good
for most production systems. In a production environment,
key_buffer_size should be larger than the default 8MB size.
large_pages
severity: note
Large pages are enabled.
locked_in_memory
severity: note
The server is locked in memory with --memlock.
log_warnings-1
severity: note
Log_warnings is disabled, so unusual events such as statements
unsafe for replication and aborted connections will not be logged
to the error log.
log_warnings-2
severity: note
Log_warnings must be set greater than 1 to log unusual events such
as aborted connections.
low_priority_updates
severity: note
The server is running with non-default lock priority for updates.
This could cause update queries to wait unexpectedly for read
queries.
max_binlog_size
severity: note
The max_binlog_size is smaller than the default of 1GB.
max_connect_errors
severity: note
max_connect_errors should probably be set as large as your platform
allows.
max_connections
severity: warn
If the server ever really has more than a thousand threads running,
then the system is likely to spend more time scheduling threads
than really doing useful work. This variable's value should be
considered in light of your workload.
myisam_repair_threads
severity: note
myisam_repair_threads > 1 enables multi-threaded repair, which is
relatively untested and is still listed as beta-quality code in the
official documentation.
old_passwords
severity: warn
Old-style passwords are insecure. They are sent in plain text
across the wire.
optimizer_prune_level
severity: warn
The optimizer will use an exhaustive search when planning complex
queries, which can cause the planning process to take a long time.
port
severity: note
The server is listening on a non-default port.
query_cache_size-1
severity: note
The query cache does not scale to large sizes and can cause
unstable performance when larger than 128MB, especially on multi-
core machines.
query_cache_size-2
severity: warn
The query cache can cause severe performance problems when it is
larger than 256MB, especially on multi-core machines.
read_buffer_size-1
severity: note
The read_buffer_size variable should generally be left at its
default unless an expert determines it is necessary to change it.
read_buffer_size-2
severity: warn
The read_buffer_size variable should not be larger than 8MB. It
should generally be left at its default unless an expert determines
it is necessary to change it. Making it larger than 2MB can hurt
performance significantly, and can make the server crash, swap to
death, or just become extremely unstable.
read_rnd_buffer_size-1
severity: note
The read_rnd_buffer_size variable should generally be left at its
default unless an expert determines it is necessary to change it.
read_rnd_buffer_size-2
severity: warn
The read_rnd_buffer_size variable should not be larger than 4M. It
should generally be left at its default unless an expert determines
it is necessary to change it.
relay_log_space_limit
severity: warn
Setting relay_log_space_limit can cause replicas to stop fetching
binary logs from their master immediately. This could increase the
risk that your data will be lost if the master crashes. If the
replicas have encountered a limit on relay log space, then it is
possible that the latest transactions exist only on the master and
no replica has retrieved them.
slave_net_timeout
severity: warn
This variable is set too high. This is too long to wait before
noticing that the connection to the master has failed and retrying.
This should probably be set to 60 seconds or less. It is also a
good idea to use pt-heartbeat to ensure that the connection does
not appear to time out when the master is simply idle.
slave_skip_errors
severity: crit
You should not set this option. If replication is having errors,
you need to find and resolve the cause of that; it is likely that
your slave's data is different from the master. You can find out
with pt-table-checksum.
sort_buffer_size-1
severity: note
The sort_buffer_size variable should generally be left at its
default unless an expert determines it is necessary to change it.
sort_buffer_size-2
severity: note
The sort_buffer_size variable should generally be left at its
default unless an expert determines it is necessary to change it.
Making it larger than a few MB can hurt performance significantly,
and can make the server crash, swap to death, or just become
extremely unstable.
sql_notes
severity: note
This server is configured not to log Note level warnings to the
error log.
sync_frm
severity: warn
It is best to set sync_frm so that .frm files are flushed safely to
disk in case of a server crash.
tx_isolation-1
severity: note
This server's transaction isolation level is non-default.
tx_isolation-2
severity: warn
Most applications should use the default REPEATABLE-READ
transaction isolation level, or in a few cases READ-COMMITTED.
expire_logs_days
severity: warn
Binary logs are enabled, but automatic purging is not enabled. If
you do not purge binary logs, your disk will fill up. If you
delete binary logs externally to MySQL, you will cause unwanted
behaviors. Always ask MySQL to purge obsolete logs, never delete
them externally.
innodb_file_io_threads
severity: note
This option is useless except on Windows.
innodb_data_file_path
severity: note
Auto-extending InnoDB files can consume a lot of disk space that is
very difficult to reclaim later. Some people prefer to set
innodb_file_per_table and allocate a fixed-size file for ibdata1.
innodb_flush_method
severity: note
Most production database servers that use InnoDB should set
innodb_flush_method to O_DIRECT to avoid double-buffering, unless
the I/O system is very low performance.
innodb_locks_unsafe_for_binlog
severity: warn
This option makes point-in-time recovery from binary logs, and
replication, untrustworthy if statement-based logging is used.
innodb_support_xa
severity: warn
MySQL's internal XA transaction support between InnoDB and the
binary log is disabled. The binary log might not match InnoDB's
state after crash recovery, and replication might drift out of sync
due to out-of-order statements in the binary log.
log_bin
severity: warn
Binary logging is disabled, so point-in-time recovery and
replication are not possible.
log_output
severity: warn
Directing log output to tables has a high performance impact.
max_relay_log_size
severity: note
A custom max_relay_log_size is defined.
myisam_recover_options
severity: warn
myisam_recover_options should be set to some value such as
BACKUP,FORCE to ensure that table corruption is noticed.
storage_engine
severity: note
The server is using a non-standard storage engine as default.
sync_binlog
severity: warn
Binary logging is enabled, but sync_binlog isn't configured so that
every transaction is flushed to the binary log for durability.
tmp_table_size
severity: note
The effective minimum size of in-memory implicit temporary tables
used internally during query execution is min(tmp_table_size,
max_heap_table_size), so max_heap_table_size should be at least as
large as tmp_table_size.
old mysql version
severity: warn
These are the recommended minimum version for each major release:
3.23, 4.1.20, 5.0.37, 5.1.30.
end-of-life mysql version
severity: note
Every release older than 5.1 is now officially end-of-life.
OPTIONS
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.
--help
Show help and exit.
--host
short form: -h; type: string
Connect to host.
--ignore-rules
type: hash
Ignore these rule IDs.
Specify a comma-separated list of rule IDs (e.g.
LIT.001,RES.002,etc.) to ignore.
--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.
--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.
--socket
short form: -S; type: string
Socket file to use for connection.
--source-of-variables
type: string; default: mysql
Read "SHOW VARIABLES" from this source. Possible values are
"mysql", "none" or a file name. If "mysql" is specified then you
must also specify a DSN on the command line.
--user
short form: -u; type: string
User for login if not current user.
--verbose
short form: -v; cumulative: yes; default: 1
Increase verbosity of output. At the default level of verbosity,
the program prints only the first sentence of each rule's
description. At higher levels, the program prints more of the
description.
--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
<https://www.percona.com/version-check>.
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.
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-variable-advisor ... > 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-variable-advisor>. Please report bugs at <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/> 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
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
This program is copyright 2010-2016 Percona LLC and/or its affiliates. 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-variable-advisor 2.2.20
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