Provided by: percona-toolkit_3.0.13-1_all bug

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 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>.

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://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

       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 2010-2018 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 3.0.13

POD ERRORS

       Hey! The above document had some coding errors, which are explained below:

       Around line 6073:
           Non-ASCII character seen before =encoding in 'Percona’s'. Assuming UTF-8