MySQL Percona Tool Kit

Kill queries running longer than 60s:
pt-kill --busy-time 60 --kill
Print, do not kill, queries running longer than 60s:
pt-kill --busy-time 60 --print
Print all login processes:
pt-kill --match-state login --print --victims all
Find all tables created more than a day ago, which use the MyISAM engine, and print their names:
 pt-find --ctime +1 --engine MyISAM
Find InnoDB tables and convert them to MyISAM:
pt-find --engine InnoDB --exec "ALTER TABLE %D.%N ENGINE=MyISAM"
Find empty tables in the test and junk databases, and delete them:
pt-find --empty junk test --exec-plus "DROP TABLE %s"
Find tables more than five gigabytes in total size:
pt-find --tablesize +5G
Summarize MySQL information nicely:
pt-mysql-summary --user=root
Diff MySQL configuration files and server variables:
Diff host1 config from SHOW VARIABLES against host2:
pt-config-diff h=host1 h=host2
Diff config from [mysqld] section in my.cnf against host1 config:
pt-config-diff /etc/my.cnf h=host1
Diff the [mysqld] section of two option files:
pt-config-diff /etc/my-small.cnf /etc/my-large.cnf
Print deadlocks on host1:
pt-deadlock-logger h=host1
Print deadlocks on host1 once then exit:
pt-deadlock-logger h=host1 --iterations 1
Save deadlocks on host1 to percona_schema.deadlocks on host2:
pt-deadlock-logger h=host1 --dest h=host2,D=percona_schema,t=deadlocks
Analyze MySQL queries from logs, processlist, and tcpdump
Report the slowest queries from slow.log:
pt-query-digest slow.log
Report the slowest queries from the processlist on host1:
pt-query-digest --processlist h=host1
Capture MySQL protocol data with tcppdump, then report the slowest queries:
tcpdump -s 65535 -x -nn -q -tttt -i any -c 1000 port 3306 > mysql.tcp.txt
pt-query-digest --type tcpdump mysql.tcp.txt
Archive rows from a MySQL table into another table or a file.
Archive all rows from oltp_server to olap_server and to a file:
pt-archiver --source h=oltp_server,D=test,t=tbl --dest h=olap_server \
--file '/var/log/archive/%Y-%m-%d-%D.%t'                           \
--where "1=1" --limit 1000 --commit-each
Purge (delete) orphan rows from child table:
pt-archiver --source h=host,D=db,t=child --purge \
--where 'NOT EXISTS(SELECT * FROM parent WHERE col=child.col)'
Verify MySQL replication integrity:
checksum every table, and report the results on every detected replica:
pt-table-checksum
Collect forensic data about MySQL when problems occur:
pt-stalk [OPTIONS]
pt-stalk waits for a trigger condition to occur, then collects data to help diagnose problems.
The tool is designed to run as a daemon with root privileges, so that you can diagnose intermittent problems that you cannot observe directly. You can also use it to execute a custom command, or to collect data on demand without waiting for the trigger to occur.

Ref.:
https://www.percona.com/doc/percona-toolkit/LATEST/pt-stalk.html
https://www.percona.com/sites/default/files/presentations/5_Percona_Toolkit_Tools_Save_Day_4.3.13.pdf
https://www.percona.com/doc/percona-toolkit/LATEST/pt-kill.htmlhttps://www.percona.com/doc/percona-toolkit/3.0/index.html

Pytohn MySQL Online Schema Change:
https://code.facebook.com/posts/1290069194423954
Percona Online Schema Change - https://www.percona.com/doc/percona-toolkit/2.2/pt-online-schema-change.html#cmdoption-pt-online-schema-change--alter-foreign-keys-method
AMAZON RDS - http://mrafayaleem.com/2016/02/08/live-mysql-schema-changes-with-percona/
https://severalnines.com/blog/online-schema-change-mysql-mariadb-comparing-github-s-gh-ost-vs-pt-online-schema-change
https://signalvnoise.com/posts/3174-taking-the-pain-out-of-mysql-schema-changes