前言

本文主要讲述如何使用 pt-query-digest 工具对 RDS MySQL 的 slow log 进行分析。

关于 RDS MySQL
MySQL 是世界上最流行的开源关系数据库，而 Amazon RDS 让你能够在云中轻松设置、操作和扩展 MySQL 部署。借助 Amazon RDS ，您可以在几分钟内快速部署可扩展的 MySQL 服务器，不仅经济实惠，还可以根据需要随时调整硬件容量的大小。

Amazon RDS for MySQL 可以管理备份、软件修补、监控、扩展和复制等耗时的数据库管理任务，让你能专注于应用程序开发和提供业务竞争力。

Amazon RDS 目前支持 5.5、5.6、5.7 和 8.0 版 MySQL Community Edition。

关于 pt-query-digest
对于数据库的日常管理工作，性能管理肯定会是占比最大的一块，“工欲善其事必先利其器”，一个好的性能分析工具会极大的提高数据库性能管理的效率，而 pt-query-digest 就是专门针对 MySQL 数据库慢查询日志的一个强力分析工具，相比于 mysqldumpslow ，其分析结果更加具体和完善。

pt-query-digest 属于 Percona Toolkit 工具集中最常用的一种，号称 MySQL DBA 必备工具之一，其能够分析MySQL数据库的 slow log 、 general log 、 binary log 文件，同时也可以使用 show processlist 或从tcpdump 抓取的 MySQL 协议数据来进行分析。

安装 Percona Toolkit

安装最新的 percona release package

[root@ip-172-31-36-44 ~]# yum install https://repo.percona.com/yum/percona-release-latest.noarch.rpm
Loaded plugins: amazon-id, rhui-lb, search-disabled-repos
percona-release-latest.noarch.rpm                                                                                                                         |  16 kB  00:00:00     
Examining /var/tmp/yum-root-jxf0g4/percona-release-latest.noarch.rpm: percona-release-1.0-9.noarch
Marking /var/tmp/yum-root-jxf0g4/percona-release-latest.noarch.rpm to be installed
Resolving Dependencies
--> Running transaction check
---> Package percona-release.noarch 0:1.0-9 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=================================================================================================================================================================================
Package                                    Arch                              Version                            Repository                                                 Size
=================================================================================================================================================================================
Installing:
percona-release                            noarch                            1.0-9                              /percona-release-latest.noarch                             18 k

Transaction Summary
=================================================================================================================================================================================
Install  1 Package

Total size: 18 k
Installed size: 18 k
Is this ok [y/d/N]: y
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : percona-release-1.0-9.noarch                                                                                                                                  1/1 
* Enabling the Percona Original repository
<*> All done!
The percona-release package now contains a percona-release script that can enable additional repositories for our newer products.

For example, to enable the Percona Server 8.0 repository use:

  percona-release setup ps80

Note: To avoid conflicts with older product versions, the percona-release setup command may disable our original repository for some products.

For more information, please visit:
  https://www.percona.com/doc/percona-repo-config/percona-release.html

  Verifying  : percona-release-1.0-9.noarch                                                                                                                                  1/1 

Installed:
  percona-release.noarch 0:1.0-9                                                                                                                                                 

Complete!
[root@ip-172-31-36-44 ~]#


[root@ip-172-31-36-44 ~]# ls -ltr /etc/yum.repos.d/
total 24
-rw-r--r--. 1 root root 8679 Mar 18 03:32 redhat-rhui.repo
-rw-r--r--. 1 root root   90 Mar 18 03:32 rhui-load-balancers.conf
-rw-r--r--. 1 root root  607 Mar 18 03:32 redhat-rhui-client-config.repo
-rw-r--r--. 1 root root  780 Mar 18 03:55 percona-original-release.repo
[root@ip-172-31-36-44 ~]# 
[root@ip-172-31-36-44 ~]# rpm -aq|grep percona
percona-release-1.0-9.noarch
percona-toolkit-3.0.13-1.el7.x86_64
[root@ip-172-31-36-44 ~]#

安装 percona toolkit

[root@ip-172-31-36-44 ~]# yum install percona-toolkit
Loaded plugins: amazon-id, rhui-lb, search-disabled-repos
Resolving Dependencies
--> Running transaction check
---> Package percona-toolkit.x86_64 0:3.0.13-1.el7 will be installed
--> Processing Dependency: perl(DBI) >= 1.13 for package: percona-toolkit-3.0.13-1.el7.x86_64
--> Processing Dependency: perl(DBD::mysql) >= 1.0 for package: percona-toolkit-3.0.13-1.el7.x86_64
--> Processing Dependency: perl(IO::Socket::SSL) for package: percona-toolkit-3.0.13-1.el7.x86_64
--> Processing Dependency: perl(Digest::MD5) for package: percona-toolkit-3.0.13-1.el7.x86_64
--> Processing Dependency: perl(Term::ReadKey) for package: percona-toolkit-3.0.13-1.el7.x86_64
--> Running transaction check
---> Package perl-DBD-MySQL.x86_64 0:4.023-6.el7 will be installed
---> Package perl-DBI.x86_64 0:1.627-4.el7 will be installed
--> Processing Dependency: perl(RPC::PlClient) >= 0.2000 for package: perl-DBI-1.627-4.el7.x86_64
--> Processing Dependency: perl(RPC::PlServer) >= 0.2001 for package: perl-DBI-1.627-4.el7.x86_64
--> Processing Dependency: perl(Data::Dumper) for package: perl-DBI-1.627-4.el7.x86_64
---> Package perl-Digest-MD5.x86_64 0:2.52-3.el7 will be installed
--> Processing Dependency: perl(Digest::base) >= 1.00 for package: perl-Digest-MD5-2.52-3.el7.x86_64
---> Package perl-IO-Socket-SSL.noarch 0:1.94-7.el7 will be installed
--> Processing Dependency: perl(IO::Socket::IP) >= 0.20 for package: perl-IO-Socket-SSL-1.94-7.el7.noarch
--> Processing Dependency: perl(Net::SSLeay) >= 1.21 for package: perl-IO-Socket-SSL-1.94-7.el7.noarch
--> Processing Dependency: perl-Net-SSLeay >= 1.55-5 for package: perl-IO-Socket-SSL-1.94-7.el7.noarch
--> Processing Dependency: perl(Mozilla::CA) for package: perl-IO-Socket-SSL-1.94-7.el7.noarch
--> Processing Dependency: perl(Net::LibIDN) for package: perl-IO-Socket-SSL-1.94-7.el7.noarch
--> Processing Dependency: perl(Net::SSLeay) for package: perl-IO-Socket-SSL-1.94-7.el7.noarch
---> Package perl-TermReadKey.x86_64 0:2.30-20.el7 will be installed
--> Running transaction check
---> Package perl-Data-Dumper.x86_64 0:2.145-3.el7 will be installed
---> Package perl-Digest.noarch 0:1.17-245.el7 will be installed
---> Package perl-IO-Socket-IP.noarch 0:0.21-5.el7 will be installed
---> Package perl-Mozilla-CA.noarch 0:20130114-5.el7 will be installed
---> Package perl-Net-LibIDN.x86_64 0:0.12-15.el7 will be installed
---> Package perl-Net-SSLeay.x86_64 0:1.55-6.el7 will be installed
---> Package perl-PlRPC.noarch 0:0.2020-14.el7 will be installed
--> Processing Dependency: perl(Net::Daemon) >= 0.13 for package: perl-PlRPC-0.2020-14.el7.noarch
--> Processing Dependency: perl(Compress::Zlib) for package: perl-PlRPC-0.2020-14.el7.noarch
--> Processing Dependency: perl(Net::Daemon::Log) for package: perl-PlRPC-0.2020-14.el7.noarch
--> Processing Dependency: perl(Net::Daemon::Test) for package: perl-PlRPC-0.2020-14.el7.noarch
--> Running transaction check
---> Package perl-IO-Compress.noarch 0:2.061-2.el7 will be installed
--> Processing Dependency: perl(Compress::Raw::Bzip2) >= 2.061 for package: perl-IO-Compress-2.061-2.el7.noarch
--> Processing Dependency: perl(Compress::Raw::Zlib) >= 2.061 for package: perl-IO-Compress-2.061-2.el7.noarch
---> Package perl-Net-Daemon.noarch 0:0.48-5.el7 will be installed
--> Running transaction check
---> Package perl-Compress-Raw-Bzip2.x86_64 0:2.061-3.el7 will be installed
---> Package perl-Compress-Raw-Zlib.x86_64 1:2.061-4.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=================================================================================================================================================================================
Package                                       Arch                         Version                                 Repository                                              Size
=================================================================================================================================================================================
Installing:
percona-toolkit                               x86_64                       3.0.13-1.el7                            percona-release-x86_64                                 7.4 M
Installing for dependencies:
perl-Compress-Raw-Bzip2                       x86_64                       2.061-3.el7                             rhui-REGION-rhel-server-releases                        32 k
perl-Compress-Raw-Zlib                        x86_64                       1:2.061-4.el7                           rhui-REGION-rhel-server-releases                        57 k
perl-DBD-MySQL                                x86_64                       4.023-6.el7                             rhui-REGION-rhel-server-releases                       140 k
perl-DBI                                      x86_64                       1.627-4.el7                             rhui-REGION-rhel-server-releases                       802 k
perl-Data-Dumper                              x86_64                       2.145-3.el7                             rhui-REGION-rhel-server-releases                        47 k
perl-Digest                                   noarch                       1.17-245.el7                            rhui-REGION-rhel-server-releases                        23 k
perl-Digest-MD5                               x86_64                       2.52-3.el7                              rhui-REGION-rhel-server-releases                        30 k
perl-IO-Compress                              noarch                       2.061-2.el7                             rhui-REGION-rhel-server-releases                       260 k
perl-IO-Socket-IP                             noarch                       0.21-5.el7                              rhui-REGION-rhel-server-releases                        36 k
perl-IO-Socket-SSL                            noarch                       1.94-7.el7                              rhui-REGION-rhel-server-releases                       114 k
perl-Mozilla-CA                               noarch                       20130114-5.el7                          rhui-REGION-rhel-server-releases                        11 k
perl-Net-Daemon                               noarch                       0.48-5.el7                              rhui-REGION-rhel-server-releases                        51 k
perl-Net-LibIDN                               x86_64                       0.12-15.el7                             rhui-REGION-rhel-server-releases                        28 k
perl-Net-SSLeay                               x86_64                       1.55-6.el7                              rhui-REGION-rhel-server-releases                       286 k
perl-PlRPC                                    noarch                       0.2020-14.el7                           rhui-REGION-rhel-server-releases                        36 k
perl-TermReadKey                              x86_64                       2.30-20.el7                             rhui-REGION-rhel-server-releases                        31 k
Transaction Summary
=================================================================================================================================================================================
Install  1 Package (+16 Dependent packages)

Total download size: 9.4 M
Installed size: 12 M
Is this ok [y/d/N]: y
Downloading packages:
(1/17): perl-Compress-Raw-Bzip2-2.061-3.el7.x86_64.rpm                                                                                                    |  32 kB  00:00:00     
(2/17): perl-Compress-Raw-Zlib-2.061-4.el7.x86_64.rpm                                                                                                     |  57 kB  00:00:00     
(3/17): perl-DBD-MySQL-4.023-6.el7.x86_64.rpm                                                                                                             | 140 kB  00:00:00     
(4/17): perl-Data-Dumper-2.145-3.el7.x86_64.rpm                                                                                                           |  47 kB  00:00:00     
(5/17): perl-DBI-1.627-4.el7.x86_64.rpm                                                                                                                   | 802 kB  00:00:00     
(6/17): perl-Digest-1.17-245.el7.noarch.rpm                                                                                                               |  23 kB  00:00:00     
(7/17): perl-Digest-MD5-2.52-3.el7.x86_64.rpm                                                                                                             |  30 kB  00:00:00     
(8/17): perl-IO-Compress-2.061-2.el7.noarch.rpm                                                                                                           | 260 kB  00:00:00     
(9/17): perl-IO-Socket-IP-0.21-5.el7.noarch.rpm                                                                                                           |  36 kB  00:00:00     
(10/17): perl-IO-Socket-SSL-1.94-7.el7.noarch.rpm                                                                                                         | 114 kB  00:00:00     
(11/17): perl-Mozilla-CA-20130114-5.el7.noarch.rpm                                                                                                        |  11 kB  00:00:00     
(12/17): perl-Net-Daemon-0.48-5.el7.noarch.rpm                                                                                                            |  51 kB  00:00:00     
(13/17): perl-Net-LibIDN-0.12-15.el7.x86_64.rpm                                                                                                           |  28 kB  00:00:00     
(14/17): perl-PlRPC-0.2020-14.el7.noarch.rpm                                                                                                              |  36 kB  00:00:00     
(15/17): perl-Net-SSLeay-1.55-6.el7.x86_64.rpm                                                                                                            | 286 kB  00:00:00     
(16/17): perl-TermReadKey-2.30-20.el7.x86_64.rpm                                                                                                          |  31 kB  00:00:00     
(17/17): percona-toolkit-3.0.13-1.el7.x86_64.rpm                                                                                                          | 7.4 MB  00:00:03     
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Total                                                                                                                                            2.4 MB/s | 9.4 MB  00:00:03     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : perl-Digest-1.17-245.el7.noarch                                                                                                                              1/17 
  Installing : perl-Digest-MD5-2.52-3.el7.x86_64                                                                                                                            2/17 
  Installing : perl-Compress-Raw-Bzip2-2.061-3.el7.x86_64                                                                                                                   3/17 
  Installing : perl-Net-LibIDN-0.12-15.el7.x86_64                                                                                                                           4/17 
  Installing : 1:perl-Compress-Raw-Zlib-2.061-4.el7.x86_64                                                                                                                  5/17 
  Installing : perl-IO-Compress-2.061-2.el7.noarch                                                                                                                          6/17 
  Installing : perl-Net-SSLeay-1.55-6.el7.x86_64                                                                                                                            7/17 
  Installing : perl-IO-Socket-IP-0.21-5.el7.noarch                                                                                                                          8/17 
  Installing : perl-Data-Dumper-2.145-3.el7.x86_64                                                                                                                          9/17 
  Installing : perl-TermReadKey-2.30-20.el7.x86_64                                                                                                                         10/17 
  Installing : perl-Net-Daemon-0.48-5.el7.noarch                                                                                                                           11/17 
  Installing : perl-PlRPC-0.2020-14.el7.noarch                                                                                                                             12/17 
  Installing : perl-DBI-1.627-4.el7.x86_64                                                                                                                                 13/17 
  Installing : perl-DBD-MySQL-4.023-6.el7.x86_64                                                                                                                           14/17 
  Installing : perl-Mozilla-CA-20130114-5.el7.noarch                                                                                                                       15/17 
  Installing : perl-IO-Socket-SSL-1.94-7.el7.noarch                                                                                                                        16/17 
  Installing : percona-toolkit-3.0.13-1.el7.x86_64                                                                                                                         17/17 
  Verifying  : perl-Mozilla-CA-20130114-5.el7.noarch                                                                                                                        1/17 
  Verifying  : perl-Net-Daemon-0.48-5.el7.noarch                                                                                                                            2/17 
  Verifying  : perl-TermReadKey-2.30-20.el7.x86_64                                                                                                                          3/17 
  Verifying  : perl-Data-Dumper-2.145-3.el7.x86_64                                                                                                                          4/17 
  Verifying  : perl-Digest-MD5-2.52-3.el7.x86_64                                                                                                                            5/17 
  Verifying  : perl-IO-Socket-IP-0.21-5.el7.noarch                                                                                                                          6/17 
  Verifying  : percona-toolkit-3.0.13-1.el7.x86_64                                                                                                                          7/17 
  Verifying  : perl-DBD-MySQL-4.023-6.el7.x86_64                                                                                                                            8/17 
  Verifying  : perl-PlRPC-0.2020-14.el7.noarch                                                                                                                              9/17 
  Verifying  : perl-Net-SSLeay-1.55-6.el7.x86_64                                                                                                                           10/17 
  Verifying  : 1:perl-Compress-Raw-Zlib-2.061-4.el7.x86_64                                                                                                                 11/17 
  Verifying  : perl-Net-LibIDN-0.12-15.el7.x86_64                                                                                                                          12/17 
  Verifying  : perl-Compress-Raw-Bzip2-2.061-3.el7.x86_64                                                                                                                  13/17 
  Verifying  : perl-Digest-1.17-245.el7.noarch                                                                                                                             14/17 
  Verifying  : perl-DBI-1.627-4.el7.x86_64                                                                                                                                 15/17 
  Verifying  : perl-IO-Compress-2.061-2.el7.noarch                                                                                                                         16/17 
  Verifying  : perl-IO-Socket-SSL-1.94-7.el7.noarch                                                                                                                        17/17 

Installed:
  percona-toolkit.x86_64 0:3.0.13-1.el7                                                                                                                                          

Dependency Installed:
  perl-Compress-Raw-Bzip2.x86_64 0:2.061-3.el7   perl-Compress-Raw-Zlib.x86_64 1:2.061-4.el7   perl-DBD-MySQL.x86_64 0:4.023-6.el7       perl-DBI.x86_64 0:1.627-4.el7          
  perl-Data-Dumper.x86_64 0:2.145-3.el7          perl-Digest.noarch 0:1.17-245.el7             perl-Digest-MD5.x86_64 0:2.52-3.el7       perl-IO-Compress.noarch 0:2.061-2.el7  
  perl-IO-Socket-IP.noarch 0:0.21-5.el7          perl-IO-Socket-SSL.noarch 0:1.94-7.el7        perl-Mozilla-CA.noarch 0:20130114-5.el7   perl-Net-Daemon.noarch 0:0.48-5.el7    
  perl-Net-LibIDN.x86_64 0:0.12-15.el7           perl-Net-SSLeay.x86_64 0:1.55-6.el7           perl-PlRPC.noarch 0:0.2020-14.el7         perl-TermReadKey.x86_64 0:2.30-20.el7  

Complete!
[root@ip-172-31-36-44 ~]#

验证 pt-queyr-digest 是否可以使用

[root@ip-172-31-36-44 ~]# pt-query-digest --help
pt-query-digest analyzes MySQL queries from slow, general, and binary log files.
It can also analyze queries from C<SHOW PROCESSLIST> and MySQL protocol data
from tcpdump.  By default, queries are grouped by fingerprint and reported in
descending order of query time (i.e. the slowest queries first).  If no C<FILES>
are given, the tool reads C<STDIN>.  The optional C<DSN> is used for certain
options like L<"--since"> and L<"--until">.  For more details, please use the
--help option, or try 'perldoc /bin/pt-query-digest' for complete documentation.

Usage: pt-query-digest [OPTIONS] [FILES] [DSN]

Options:

  --ask-pass                   Prompt for a password when connecting to MySQL
  --attribute-aliases=a        List of attribute|alias,etc (default db|Schema)
  --attribute-value-limit=i    A sanity limit for attribute values (default 0)
  --charset=s              -A  Default character set
  --config=A                   Read this comma-separated list of config files;
                               if specified, this must be the first option on
                               the command line
  --[no]continue-on-error      Continue parsing even if there is an error (
                               default yes)
  --[no]create-history-table   Create the --history table if it does not exist (
                               default yes)
  --[no]create-review-table    Create the --review table if it does not exist (
                               default yes)
  --daemonize                  Fork to the background and detach from the shell
  --database=s             -D  Connect to this database
  --defaults-file=s        -F  Only read mysql options from the given file
  --embedded-attributes=a      Two Perl regex patterns to capture pseudo-
                               attributes embedded in queries
  --expected-range=a           Explain items when there are more or fewer than
                               expected (default 5,10)
  --explain=d                  Run EXPLAIN for the sample query with this DSN
                               and print results
  --filter=s                   Discard events for which this Perl code doesn't
                               return true
  --group-by=A                 Which attribute of the events to group by (
                               default fingerprint)
  --help                       Show help and exit
  --history=d                  Save metrics for each query class in the given
                               table. pt-query-digest saves query metrics (
                               query time, lock time, etc.) to this table so
                               you can see how query classes change over time
  --host=s                 -h  Connect to host
  --ignore-attributes=a        Do not aggregate these attributes (default arg,
                               cmd, insert_id, ip, port, Thread_id, timestamp,
                               exptime, flags, key, res, val, server_id,
                               offset, end_log_pos, Xid)
  --inherit-attributes=a       If missing, inherit these attributes from the
                               last event that had them (default db,ts)
  --interval=f                 How frequently to poll the processlist, in
                               seconds (default .1)
  --iterations=i               How many times to iterate through the collect-
                               and-report cycle (default 1)
  --limit=A                    Limit output to the given percentage or count (
                               default 95%:20)
  --log=s                      Print all output to this file when daemonized
  --max-hostname-length=i      Trim host names in reports to this length. 0=Do
                               not trim host names (default 10)
  --max-line-length=i          Trim lines to this length. 0=Do not trim lines (
                               default 74)
  --order-by=A                 Sort events by this attribute and aggregate
                               function (default Query_time:sum)
  --outliers=a                 Report outliers by attribute:percentile:count (
                               default Query_time:1:10)
  --output=s                   How to format and print the query analysis
                               results (default report)
  --password=s             -p  Password to use when connecting
  --pid=s                      Create the given PID file
  --port=i                 -P  Port number to use for connection
  --preserve-embedded-numbers  Preserve numbers in database/table names when
                               fingerprinting queries
  --processlist=d              Poll this DSN's processlist for queries, with --
                               interval sleep between
  --progress=a                 Print progress reports to STDERR (default time,
                               30)
  --read-timeout=m             Wait this long for an event from the input; 0 to
                               wait forever (default 0).  Optional suffix s=
                               seconds, m=minutes, h=hours, d=days; if no
                               suffix, s is used.
  --[no]report                 Print query analysis reports for each --group-by
                               attribute (default yes)
  --report-all                 Report all queries, even ones that have been
                               reviewed
  --report-format=A            Print these sections of the query analysis
                               report (default rusage,date,hostname,files,
                               header,profile,query_report,prepared)
  --report-histogram=s         Chart the distribution of this attribute's
                               values (default Query_time)
  --resume=s                   If specified, the tool writes the last file
                               offset, if there is one, to the given filename
  --review=d                   Save query classes for later review, and don't
                               report already reviewed classes
  --run-time=m                 How long to run for each --iterations.  Optional
                               suffix s=seconds, m=minutes, h=hours, d=days; if
                               no suffix, s is used.
  --run-time-mode=s            Set what the value of --run-time operates on (
                               default clock)
  --sample=i                   Filter out all but the first N occurrences of
                               each query
  --set-vars=A                 Set the MySQL variables in this comma-separated
                               list of variable=value pairs
  --show-all=H                 Show all values for these attributes
  --since=s                    Parse only queries newer than this value (parse
                               queries since this date)
  --slave-password=s           Sets the password to be used to connect to the
                               slaves
  --slave-user=s               Sets the user to be used to connect to the slaves
  --socket=s               -S  Socket file to use for connection
  --timeline                   Show a timeline of events
  --type=A                     The type of input to parse (default slowlog)
  --until=s                    Parse only queries older than this value (parse
                               queries until this date)
  --user=s                 -u  User for login if not current user
  --variations=A               Report the number of variations in these
                               attributes' values
  --version                    Show version and exit
  --[no]version-check          Check for the latest version of Percona Toolkit,
                               MySQL, and other programs (default yes)
  --[no]vertical-format        Output a trailing "\G" in the reported SQL
                               queries (default yes)
  --watch-server=s             This option tells pt-query-digest which server
                               IP address and port (like "10.0.0.1:3306") to
                               watch when parsing tcpdump (for --type tcpdump);
                               all other servers are ignored

Option types: s=string, i=integer, f=float, h/H/a/A=comma-separated list, d=DSN, z=size, m=time

Rules:

  This tool accepts additional command-line arguments. Refer to the SYNOPSIS and usage information for details.

DSN syntax is key=value[,key=value...]  Allowable DSN keys:

  KEY  COPY  MEANING
  ===  ====  =============================================
  A    yes   Default character set
  D    yes   Default database to use when connecting to MySQL
  F    yes   Only read default options from the given file
  P    yes   Port number to use for connection
  S    yes   Socket file to use for connection
  h    yes   Connect to host
  p    yes   Password to use when connecting
  t    no    The --review or --history table
  u    yes   User for login if not current user

  If the DSN is a bareword, the word is treated as the 'h' key.

Options and values after processing arguments:

  --ask-pass                   FALSE
  --attribute-aliases          db|Schema
  --attribute-value-limit      0
  --charset                    (No value)
  --config                     /etc/percona-toolkit/percona-toolkit.conf,/etc/percona-toolkit/pt-query-digest.conf,/root/.percona-toolkit.conf,/root/.pt-query-digest.conf
  --continue-on-error          TRUE
  --create-history-table       TRUE
  --create-review-table        TRUE
  --daemonize                  FALSE
  --database                   (No value)
  --defaults-file              (No value)
  --embedded-attributes        (No value)
  --expected-range             5,10
  --explain                    (No value)
  --filter                     (No value)
  --group-by                   fingerprint
  --help                       TRUE
  --history                    (No value)
  --host                       (No value)
  --ignore-attributes          arg,cmd,insert_id,ip,port,Thread_id,timestamp,exptime,flags,key,res,val,server_id,offset,end_log_pos,Xid
  --inherit-attributes         db,ts
  --interval                   .1
  --iterations                 1
  --limit                      95%:20
  --log                        (No value)
  --max-hostname-length        10
  --max-line-length            74
  --order-by                   Query_time:sum
  --outliers                   Query_time:1:10
  --output                     report
  --password                   (No value)
  --pid                        (No value)
  --port                       (No value)
  --preserve-embedded-numbers  FALSE
  --processlist                (No value)
  --progress                   time,30
  --read-timeout               0
  --report                     TRUE
  --report-all                 FALSE
  --report-format              rusage,date,hostname,files,header,profile,query_report,prepared
  --report-histogram           Query_time
  --resume                     (No value)
  --review                     (No value)
  --run-time                   (No value)
  --run-time-mode              clock
  --sample                     (No value)
  --set-vars                   
  --show-all                   
  --since                      (No value)
  --slave-password             (No value)
  --slave-user                 (No value)
  --socket                     (No value)
  --timeline                   FALSE
  --type                       slowlog
  --until                      (No value)
  --user                       (No value)
  --variations                 
  --version                    FALSE
  --version-check              TRUE
  --vertical-format            TRUE
  --watch-server               (No value)
[root@ip-172-31-36-44 ~]#

安装及配置 AWSCLI

这里安装awscli主要是为了后续可以使用awscli下载RDS MySQL的slow log文件到本地，供pt-query-digest进行分析。

安装 awscli

curl "https://s3.amazonaws.com/aws-cli/awscli-bundle.zip" -o "awscli-bundle.zip"
unzip awscli-bundle.zip
./awscli-bundle/install
echo "export PATH=$PATH:/root/.local/lib/aws/bin" >> ~/.bash_profile
source ~/.bash_profile
cat ~/.bash_profile

配置 awscli

[root@ip-172-31-36-44 ~]# aws configure
AWS Access Key ID [None]: AKIAXXXXXXXX6PPVDJKQ
AWS Secret Access Key [None]: BhlGgQLOjEcxxxxx/w3JxxxxxxUCI4IAra92ZJ
Default region name [None]: cn-northwest-1
Default output format [None]: 
[root@ip-172-31-36-44 ~]#

安装 MySQL 客户端

这里安装MySQL客户端主要是为了后续可以使用mysql命令进行相关sql语句的执行，以获取RDS MySQL的slow log文件到本地，供pt-query-digest进行分析。

[root@ip-172-31-36-44 ~]# yum install mariadb.x86_64 -y
Loaded plugins: amazon-id, rhui-lb, search-disabled-repos
Resolving Dependencies
--> Running transaction check
---> Package mariadb.x86_64 1:5.5.60-1.el7_5 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=================================================================================================================================================================================
Package                           Arch                             Version                                     Repository                                                  Size
=================================================================================================================================================================================
Installing:
mariadb                           x86_64                           1:5.5.60-1.el7_5                            rhui-REGION-rhel-server-releases                           8.6 M

Transaction Summary
=================================================================================================================================================================================
Install  1 Package

Total download size: 8.6 M
Installed size: 49 M
Downloading packages:
mariadb-5.5.60-1.el7_5.x86_64.rpm                                                                                                                         | 8.6 MB  00:00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : 1:mariadb-5.5.60-1.el7_5.x86_64                                                                                                                               1/1 
  Verifying  : 1:mariadb-5.5.60-1.el7_5.x86_64                                                                                                                               1/1 

Installed:
  mariadb.x86_64 1:5.5.60-1.el7_5                                                                                                                                                

Complete!
[root@ip-172-31-36-44 ~]#

使用 pt-query-digest 分析 slow log

前面我们已经完成了所有的准备工作，现在看看如何来使用 pt-query-digest 工具分析 RDS MySQL 的 slow log 文件。

如果要分析 slow log，第一步就是先要获取到 slow log 文件，由于 RDS MySQL 是托管数据库，我们无法登录到 MySQL 所在服务器，那么应该如何来获取 slow log 文件呢？

根据 MySQL slow log 的相关配置，我们知道 slow log 的存在形式一共有两种： table 或 file ，由 log_output 参数进行控制：

TABLE (默认) – 将一般查询写入 general_log 表，将慢速查询写入 mysql.slow_log 表；
FILE – 将一般查询日志和慢速查询日志写入文件系统；
NONE – 禁用日志记录；
针对不同形式的 slow log，我们有不同的方法将其下载到本地：
TABLE ：由于这是将慢查询记录存放在 MySQL 的数据表里，这里我们可以使用 sql 命令将其输出到本地的一个文件；
FILE ：慢查询日志存放在 RDS MySQL 托管主机上，我们可以利用 awscli 提供的 RDS API download-db-log-file-portion 将 slow log 下载到本地；
具体实现形式请参加后续对应部分的内容。

使用 sql 脚本获取 slow log

获取整个 slow log

mysql> show variables like 'log_output';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_output    | TABLE |
+---------------+-------+
1 row in set (0.03 sec)
mysql>
[root@ip-172-31-36-44 ~]# mysql -h mysql.xxxxxxxxxxxx.rds.cn-northwest-1.amazonaws.com.cn -u root -p -P13306 -D mysql -s -r -e "SELECT CONCAT( '# Time: ', DATE_FORMAT(start_time, '%y%m%d %H%i%s'), '\n', '# User@Host: ', user_host, '\n', '# Query_time: ', TIME_TO_SEC(query_time),  '  Lock_time: ', TIME_TO_SEC(lock_time), '  Rows_sent: ', rows_sent, '  Rows_examined: ', rows_examined, '\n', sql_text, ';' ) FROM mysql.slow_log" > /tmp/mysql_slow_log.log
Enter password: 
[root@ip-172-31-36-44 ~]# 
[root@ip-172-31-36-44 ~]# ls -l /tmp/mysql_slow_log.log
-rw-r--r--. 1 root root 14211651 Mar 19 02:57 /tmp/mysql_slow_log.log
[root@ip-172-31-36-44 ~]#
[root@ip-172-31-36-44 ~]# more /tmp/mysql_slow_log.log
# Time: 190130 145734
# User@Host: root[root] @  [60.223.227.126]
# Query_time: 20  Lock_time: 0  Rows_sent: 0  Rows_examined: 48413563
select * from unit_value where FT121_SET <> null
LIMIT 0, 10000;
# Time: 190130 153530
# User@Host: root[root] @ 42-2-128-026.static.netvigator.com [42.2.128.26]
# Query_time: 96  Lock_time: 0  Rows_sent: 20099504  Rows_examined: 68517265
select PT111_VALUE from unit_value WHERE PT111_VALUE <> 0 and PT111_VALUE < 1.3 ORDER by UNITNAME DESC;
# Time: 190130 153802
# User@Host: root[root] @ 42-2-128-026.static.netvigator.com [42.2.128.26]
# Query_time: 31  Lock_time: 0  Rows_sent: 579105  Rows_examined: 49576551
select DISTINCT UNITNAME,PT111_VALUE from unit_value WHERE PT111_VALUE <> 0 and PT111_VALUE < 1.3 ORDER by UNITNAME DESC;
# Time: 190130 154215
# User@Host: root[root] @  [60.223.227.126]
# Query_time: 45  Lock_time: 0  Rows_sent: 1580250  Rows_examined: 50026401
select 
UNITNAME
,first_value(PT111_VALUE) over (partition by UNITNAME order by UNITTIME)
from unit_value;

获取指定时间段的 slow log

[root@ip-172-31-36-44 ~]# mysql -h mysql.xxxxxxxxxxxx.rds.cn-northwest-1.amazonaws.com.cn -u root -p -P13306 -D mysql -s -r -e "SELECT CONCAT( '# Time: ', DATE_FORMAT(start_time, '%y%m%d %H%i%s'), '\n', '# User@Host: ', user_host, '\n', '# Query_time: ', TIME_TO_SEC(query_time),  '  Lock_time: ', TIME_TO_SEC(lock_time), '  Rows_sent: ', rows_sent, '  Rows_examined: ', rows_examined, '\n', sql_text, ';' ) FROM mysql.slow_log where DATE_FORMAT(start_time, '%Y%m%d %H:%i:%s') between '20190328 10:00:00' and '20190328 11:00:00' " > /tmp/slow.log.10-11.log
Enter password: 
[root@ip-172-31-36-44 ~]#
[root@ip-172-31-36-44 ~]# ls -l /tmp/mysql_slow_log1.log
-rw-r--r--. 1 root root 10874816 Mar 19 04:33 /tmp/mysql_slow_log1.log
[root@ip-172-31-36-44 ~]#

使用 awscli 获取 MySQL slow log

mysql> show variables like '%output%';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| innodb_status_output       | OFF   |
| innodb_status_output_locks | OFF   |
| log_output                 | FILE  |
+----------------------------+-------+
3 rows in set (0.05 sec)

mysql> 
mysql> show variables like '%slow%';
+---------------------------+----------------------------------------------+
| Variable_name             | Value                                        |
+---------------------------+----------------------------------------------+
| log_slow_admin_statements | OFF                                          |
| log_slow_slave_statements | OFF                                          |
| slow_launch_time          | 2                                            |
| slow_query_log            | ON                                           |
| slow_query_log_file       | /rdsdbdata/log/slowquery/mysql-slowquery.log |
+---------------------------+----------------------------------------------+
5 rows in set (2.07 sec)

mysql> 


[root@ip-172-31-36-44 ~]# aws rds download-db-log-file-portion --db-instance-identifier mysql --log-file-name slowquery/mysql-slowquery.log --starting-token 0 --output text> mysql-slowquery.log
[root@ip-172-31-36-44 ~]# ls -l mysql-slowquery.log 
-rw-r--r--. 1 root root 15970 Mar 19 04:41 mysql-slowquery.log
[root@ip-172-31-36-44 ~]# 

[root@ip-172-31-36-44 ~]# more mysql-slowquery.log
# Time: 2019-03-19T04:40:56.629552Z
# User@Host: root[root] @ ec2-52-82-53-253.cn-northwest-1.compute.amazonaws.com.cn [52.82.53.253]  Id: 249635335
# Query_time: 5.087165  Lock_time: 0.000052 Rows_sent: 0  Rows_examined: 1496709
use yuci;
SET timestamp=1552970456;
SELECT tagout_value.tagtime AS tagout_value_tagtime, tagout_value.tagname AS tagout_value_tagname, tagout_value.tagvalue AS tagout_value_tagvalue 
FROM tagout_value 
WHERE tagout_value.tagname = 'COV122_OUTPAR_134' ORDER BY tagout_value.tagtime DESC 
LIMIT 1;
# Time: 2019-03-19T04:40:56.819594Z
# User@Host: root[root] @ ec2-52-82-59-190.cn-northwest-1.compute.amazonaws.com.cn [52.82.59.190]  Id: 249635331
# Query_time: 5.274261  Lock_time: 0.000053 Rows_sent: 0  Rows_examined: 1496709
SET timestamp=1552970456;
SELECT tagout_value.tagtime AS tagout_value_tagtime, tagout_value.tagname AS tagout_value_tagname, tagout_value.tagvalue AS tagout_value_tagvalue 
FROM tagout_value 
WHERE tagout_value.tagname = 'COV122_OUTPAR' ORDER BY tagout_value.tagtime DESC 
LIMIT 1;

实际案例

这里描述一个实际的案例，在 RDS MySQL 碰到性能问题时，我们如何通过 pt-query-digest 工具来分析性能，找到其中的问题所在。

发现问题
某一天突然发现 RDS MySQL CPU 利用率高达100%，平时正常运行几乎都在40%以下，怀疑 MySQL 数据库之前运行了一些问题 SQL 语句导致了 CPU 资源的飙升。

分析问题
这里我们首先来获取13:00-14:00这一个小时范围内的 RDS MySQL slow log ，然后再使用我们前面部署的 pt-query-digest 工具来分析一下，看是否可以发现一些端倪。

[root@ip-172-31-36-44 ~]# mysql -h mysql. xxxxxxxxxxxx.rds.cn-northwest-1.amazonaws.com.cn -u root -p -P13306 -D mysql -s -r -e "SELECT CONCAT( '# Time: ', DATE_FORMAT(start_time, '%y%m%d %H%i%s'), '\n', '# User@Host: ', user_host, '\n', '# Query_time: ', TIME_TO_SEC(query_time),  '  Lock_time: ', TIME_TO_SEC(lock_time), '  Rows_sent: ', rows_sent, '  Rows_examined: ', rows_examined, '\n', sql_text, ';' ) FROM mysql.slow_log where DATE_FORMAT(start_time, '%Y%m%d %H:%i:%s') between '20190328 13:00:00' and '20190328 14:00:00' " > /tmp/slow.log.1314.log
Enter password: 
[root@ip-172-31-36-44 ~]# 
[root@ip-172-31-36-44 ~]# 
[root@ip-172-31-36-44 ~]# pt-query-digest --report /tmp/slow.log.1314.log> /tmp/report.1314.log
[root@ip-172-31-36-44 ~]# 
[root@ip-172-31-36-44 ~]# cat /tmp/report.1314.log 

# 220ms user time, 30ms system time, 27.48M rss, 221.73M vsz
# Current date: Thu Mar 28 06:03:53 2019
# Hostname: ip-172-31-36-44.cn-northwest-1.compute.internal
# Files: /tmp/slow.log.1314.log
# Overall: 255 total, 4 unique, 0 QPS, 0x concurrency ____________________
# Attribute          total     min     max     avg     95%  stddev  median
# ============     ======= ======= ======= ======= ======= ======= =======
# Exec time          9360s      5s     62s     37s     49s      8s     35s
# Lock time              0       0       0       0       0       0       0
# Rows sent          3.12k       0     266   12.52       0   54.70       0
# Rows examine       1.85G   1.88M  12.99M   7.45M   9.30M   1.35M   6.94M
# Query size         2.42M      78 114.10k   9.72k  79.83k  28.60k  212.52
# Time              46.29M 185.87k 185.87k 185.87k 185.87k       0 185.87k

# Profile
# Rank Query ID                       Response time   Calls R/Call  V/M   
# ==== ============================== =============== ===== ======= ===== 
#    1 0x582C46632FB388ABE5D178303... 7913.0000 84.5%   216 36.6343  1.57 SELECT MLModel?_ecgw_a_pred
#    2 0x0E39F3F13EDA325B4E53D0244...  971.0000 10.4%    25 38.8400  2.04 INSERT slph_adjust_his
#    3 0x3FC5160B3B25069FA843DC222...  466.0000  5.0%    12 38.8333  1.53 SELECT MLModel?_jd_pred unit_info MLModel?_jd_pred
# MISC 0xMISC                           10.0000  0.1%     2  5.0000   0.0 <1 ITEMS>

# Query 1: 0 QPS, 0x concurrency, ID 0x582C46632FB388ABE5D178303E079908 at byte 420282
# This item is included in the report because it matches --limit.
# Scores: V/M = 1.57
# Attribute    pct   total     min     max     avg     95%  stddev  median
# ============ === ======= ======= ======= ======= ======= ======= =======
# Count         84     216
# Exec time     84   7913s     20s     57s     37s     49s      8s     35s
# Lock time      0       0       0       0       0       0       0       0
# Rows sent      0       0       0       0       0       0       0       0
# Rows examine  79   1.48G   7.01M   7.02M   7.02M   6.94M       0   6.94M
# Query size     1  47.02k     222     223  222.89  212.52       0  212.52
# Time          84  39.21M 185.87k 185.87k 185.87k 185.87k       0 185.87k
# String:
# Hosts        172.31.39.23 (120/55%), 172.31.46.35 (36/16%)... 3 more
# Users        root
# Query_time distribution
#   1us
#  10us
# 100us
#   1ms
#  10ms
# 100ms
#    1s
#  10s+  ################################################################
# Tables
#    SHOW TABLE STATUS LIKE 'MLModel6_ecgw_a_pred'\G
#    SHOW CREATE TABLE `MLModel6_ecgw_a_pred`\G
# EXPLAIN /*!50100 PARTITIONS*/
SELECT * FROM MLModel6_ecgw_a_pred
                where  unitname = 395 and forecast48hr >= now() 
                and forecast48hr < NOW() + INTERVAL 1 HOUR 
                order by predTime desc 
                limit 1\G

# Query 2: 0 QPS, 0x concurrency, ID 0x0E39F3F13EDA325B4E53D0244F2E9A23 at byte 210412
..............
..............
..............

从上面我们可以看到排在第一位的 SQL 语句在本次分析中总的时间占比高达84%，且单次调用耗时在36秒。接下来我们看看 SQL 语句的情况：

mysql> SELECT * FROM MLModel6_ecgw_a_pred
    ->                 where  unitname = 395 and forecast48hr >= now() 
    ->                 and forecast48hr < NOW() + INTERVAL 1 HOUR 
    ->                 order by predTime desc 
    ->                 limit 1
    -> ;
Empty set (39.59 sec)
mysql> explain SELECT * FROM MLModel6_ecgw_a_pred
    ->                 where  unitname = 395 and forecast48hr >= now()
    ->                 and forecast48hr < NOW() + INTERVAL 1 HOUR
    ->                 order by predTime desc
    ->                 limit 1;
+----+-------------+----------------------+------------+-------+---------------+---------+---------+------+------+----------+----------------------------------+
| id | select_type | table                | partitions | type  | possible_keys | key     | key_len | ref  | rows | filtered | Extra                            |
+----+-------------+----------------------+------------+-------+---------------+---------+---------+------+------+----------+----------------------------------+
|  1 | SIMPLE      | MLModel6_ecgw_a_pred | NULL       | index | idx_un        | idx_un1 | 15      | NULL |  325 |     0.03 | Using where; Backward index scan |
+----+-------------+----------------------+------------+-------+---------------+---------+---------+------+------+----------+----------------------------------+
1 row in set, 1 warning (0.02 sec)


mysql> show index from MLModel6_ecgw_a_pred;
+----------------------+------------+----------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| Table                | Non_unique | Key_name | Seq_in_index | Column_name  | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
+----------------------+------------+----------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| MLModel6_ecgw_a_pred |          0 | PRIMARY  |            1 | id           | A         |     6899295 |     NULL |   NULL |      | BTREE      |         |               | YES     | NULL       |
| MLModel6_ecgw_a_pred |          1 | idx_un   |            1 | forecast48hr | A         |       60106 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
| MLModel6_ecgw_a_pred |          1 | idx_un   |            2 | UNITNAME     | A         |      352164 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
| MLModel6_ecgw_a_pred |          1 | idx_un1  |            1 | predTime     | A         |      112492 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
| MLModel6_ecgw_a_pred |          1 | idx_un1  |            2 | UNITNAME     | A         |      162489 |     NULL |   NULL | YES  | BTREE      |         |               | YES     | NULL       |
+----------------------+------------+----------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
5 rows in set (0.10 sec)

mysql>

从上面我们不难看出，此 SQL 语句使用了错误的索引 idx_un1 ，实际上使用 idx_un 索引选择性会更好，执行效率会更高。

解决问题
强制此 SQL 语句使用正确的索引，不到1秒就执行完毕：

mysql> SELECT * FROM MLModel6_ecgw_a_pred force index(idx_un)
    ->                 where  unitname = 395 and forecast48hr >= now() 
    ->                 and forecast48hr < NOW() + INTERVAL 1 HOUR 
    ->                 order by predTime desc 
    ->                 limit 1
    -> ;
Empty set (0.03 sec)

mysql>

后续就是具体的优化工作，至于是优化索引设置，还是去调整SQL语句，可以根据实际情况来进行即可。

总结

pt-query-digest 是一个针对 MySQL slow log 进行分析的工具，可以获得更友好、易读、更人性化的 SQL 性能汇总及分析报告；
RDS MySQL 由于是托管的数据库，我们可以使用 awscli RDS API 或者以 MySQL sql 脚本来分别将 FILE 和 TABLE 形式的慢查询日志获取到本地，然后再使用 pt-query-digest 进行分析；
Percona Toolkit 是业界比较知名的 MySQL 工具集，里面包含多种可以提升效率的管理工具，除了 pt-query-digest 使用较多之外，还有 pt-online-schema-change 、 pt-mysql-summary 、 pt-summary 等工具被广泛使用，推荐有兴趣的同学可以尝试使用；

作者介绍：
闫静
AWS专业服务团队咨询顾问、云架构师。具有10年以上大型数据库维护管理及架构设计经验，目前主要专注于企业客户数据库上云、整体上云架构方面的规划/设计及实施。热衷于云基础架构规划、云端数据库架构设计、大数据架构部署等领域的研究和学习。

本文转载自AWS技术博客。

原文链接：
https://amazonaws-china.com/cn/blogs/china/pt-query-digest-rds-mysql-slow-searchnew/

创作场景

使用 pt-query-digest 分析 RDS MySQL 慢查询日志