abellina / liqui-cap-online

Sample integration between Liquibase, Capistrano, and pt-online-schema-change

liqui-cap-online

Sample integration between Liquibase, Capistrano, and pt-online-schema-change

Purpose

This is a proof of concept that was simply meant to show the functionality. Essentailly, this project handles the following:

• Capturing the output of Liquibase rather than running it directly
• Parsing each statement to determine the type
• Converting CREATE INDEX statements to ALTER TABLE statements
• Switching ALTER statements to use pt-online-schema-change

The goal is to allow non-blocking deployments of database changes within a larger deployment (i.e. Capistrano) environment.

Requirements

This system was built on the following test environemnt:

• Centos 6.4
• Percona Server 5.5 website
• Capistrano (2.9.0) website
  • Requires Ruby (1.8.7), Rubygem (2.1.10)
• Liquibase (2.0.5) website
  • Requires java (1.5, not JDK) and Java MySQL connector (included)
• pt-online-schema-change (2.2.5) website

Note this was a local test VM and versions were just supplied by default yum installs

Naturally, setting these up is outside the scope of this README, but one thing I will note - when setting up using standard "yum" commands, you will need to specify the version of Capistrano as the current version doesn't work with the default Ruby/Rubygem install:

yum install ruby
yum install gcc g++ make automake autoconf curl-devel openssl-devel zlib-devel httpd-devel apr-devel apr-util-devel sqlite-devel
yum install ruby-rdoc ruby-devel
yum install rubygems
gem update --system
gem install capistrano -v 2.9.0

Samples

As part of this repo, I've included some sample changelog files that display different ALTER operations.

To use, simply create a new, empty database (mydb in this case) and then run the capfile run_liquibase_alters task 3 times, each time changing the real changelog file the master file points to:

<include file="samples/changelog_01.xml" relativeToChangelogFile="true"/>

Once you've applied the 3 changelog files, you can run the clean_old_tables task to drop the old tables left by pt-osc. Note - these tables are left by adding the --no-drop-table flag to pt-osc to help with rollbacks

The samples directory also contains the mysqldump output of the test schema after applying the chnages and also one showing the cleanup.