Handling Database Deployments

Mike Willbanks Blog: http://blog.digitalstruct.com Twitter : mwillbanks IRC : lubs Talk: http://joind.in/986 Handling Database Deployment ZendCon Unconference 2009

What We'll Cover (and not cover)
The [Somewhat] Prerequisites
Why Use Database Change Management
Why To Not Use Database Abstraction Layer Migrations
Even You Doctrine!
DBDeploy and LiquiBase
How It Works (under the hood)
Basic Syntax
Recommended Structure

The [Somewhat] Prerequisites
You should be using an issue tracking system.
You should be using source code management.
You already know how you are deploying your code.

Why Database Change Management
Do you version your code? Same reasons apply to database deltas (or change sets).
Deltas typically are a part of a code change.
Ensures the correlation between code revisions.
Allows the automation of changes.
Ensure you are keeping environments consistent.
Allows for reverting back to previous versions (some voodoo magic may be required).

The Traditional Way - #fail
Developer writes code and applies database change locally.
Developer forgets to note change on bug tracking ticket or notify anyone of the change or DBA misses the change, etc.
Code deployment and database deployment happens.
System is broken... #fail
Developer attempts to figure out what happened, “oops factor”.

A Better Way
Developer writes code and writes a database delta.
Developer tests changes locally.
Code and Database Delta is committed against a ticket (or at least together).
Pre-Deployment Database Changes are Applied.
Code Deployment is pushed out.
Post-Deployment Database Changes are Applied.
System === happiness.

Some Process Theory Simplified
Database Pre-Deployment
Apply database changes compatible with current code, in preparation for new code.
Essentially, do not break what is already out there.
Code Deployment
No more detail needed.
Database Post-Deployment
Clean up database that was compatible with old code and /or migrate to fulfill new requirements.

Database Abstraction Migrations
Many do not support pre and post migrations.
If you change your abstraction layer, you must change your migration logic.
Example Case:
Code Deployment
Database Migrations Run on 1 st Machine
What about the n+1 machines?! #fail

DBDeploy : dbdeploy.com
Java based solution - #port anyone?
Utilizes SQL delta files.
Handles undo within the delta file.
If using Ant – Issue #29 :)
Utilizes different table names to handle different deployments.
Queries the database for what has not been applied and generates a SQL file to apply towards the database.

DBDeploy : Getting Started
Install Java 1.5+
Download DBDeploy (Obvious)
Download your Java Connector
We will be using the command line version (rather than ant for this talk)
It is kind of a blackbox :)

DBDeploy : Initial Setup
Under scripts, install the SQL file for your database
Ensure you run this twice with 2 different database names. I suggest creating a pre and post changelog table.
Put the Java Connector somewhere that you can reference it.

DBDeploy : Writing a Script
Files run in the format of:
001, 002, 003... with .sql on the end.
You can add a comment on the file name:
001_created_test_table.sql
Put in your delta, then for handling an undo, put in a comment in the format of:
CREATE TABLE `xyz` (id INTEGER); --//@UNDO DROP TABLE `xyz`;
Save this file to a directory of the type of script:
You did do pre and post changelog right?

DBDeploy : An Example
java -cp mysql-connector-java-5.1.10-bin.jar:dbdeploy-cli-3.0M2.jar com.dbdeploy.CommandLineTarget -Dcom.mysql.jdbc.Driver -dmysql -sexample/ -u"jdbc:mysql://localhost/uncon2009_db" -Uuncon2009 -P***** -tchangelog_pre --outputfile deploy.sql
This will create the deploy.sql file to apply to your database.
Let's watch this command, understand the output and look at the script.

DBDeploy : The Output dbdeploy 3.0M2 Reading change scripts from directory /home/mwillbanks/presentations/zendcon-uncon-2009-db-deployments/bin/dbdeploy/example... Changes currently applied to database: (none) Scripts available: 1, 2 To be applied: 1, 2

DBDeploy : Questions?
Any questions on DBDeploy, how it works and anything I may have missed before we go on?

LiquiBase : liquibase.org
Java based solution - #port anyone?
Utilizes XML Files for Changesets
Handles undo within the changeset.
Utilizes a single table with a primary key on the id, author and filename.
Queries the database for what has not been applied and applies the different SQL.
Very well documented unlike DBDeploy.

LiquiBase : Getting Started
Install Java 1.5+
Download LiquiBase (Obvious)
Download your Java Connector
We will be using the command line version
This command line version is full featured.

LiquiBase : Initial Setup
Put the Java Connector somewhere that you can reference it (usually in the lib folder)
That's pretty much all you need initially, besides extracting the tar ball :)

LiquiBase : The Command Line
./liquibase --driver=com.mysql.jdbc.Driver --changeLogFile=../sql/pre-deployment.xml --username=uncon2009 --password=****** --url="jdbc:mysql://localhost/uncon2009_db”
Relevant Commands:
migrate – applies change sets for migration
rollback – to a tag
rollbackToDate – rollback to a date
generateChangeLog – useful to create the initial version of the change log.
changeLogSync – mark all changes as ran.
markNextChangeSetRan – mark next change as ran.

LiquiBase : Generating a Script
Files run in XML files
You can include them from a file or keep all changes in a single file.
Run the command:
./liquibase --driver=com.mysql.jdbc.Driver --changeLogFile=sql/pre.xml --username=uncon2009 --password=****** --url="jdbc:mysql://localhost/uncon2009_db” generateChangeLog
This saves the file to the area specified.

LiquiBase : Writing a Change Log <?xml version="1.0" encoding="UTF-8"?> <databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog/1.6" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog/1.6 http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-1.6.xsd"> </databaseChangeLog>
All change logs must define the XML schema:
Each change log starts with changeLog:
<changeSet id="1" author="mike"> <createTable tableName="uncon2009"> <column name="id" type="int"> <constraints primaryKey="true" nullable="false"/> </column> </createTable> </changeSet>

LiquiBase : The Internals
LiquiBase creates tables called:
DATABASECHANGELOG – this handles all of the changes, each change has a primary key on id, author and filename.
This table also creates an MD5 of each change set, so do not change a changeset unless it has an error and will not run :)
DATABASECHANGELOCK – locks to ensure you are not executing the same change sets.

LiquiBase : Examples of Migration
Running through the pre deployment file.
Running through the post deployment file.

LiquiBase : Pre-Deployment File

LiquiBase : Post-Deployment File

Conclusion
Use something to manage your database deployments.
There are tools, even more than mentioned here.
Ensure you can handle pre and post deployments.
They are important!
Read the manuals of each system
There is a bunch of items I didn't cover.
Slides will be posted with examples sometime today.
Both on my blog and I'll update the joind.in information to reference the presentation.

Mike Willbanks Blog: http://blog.digitalstruct.com Twitter : mwillbanks IRC : lubs Talk: http://joind.in/986 Questions?

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Handling Database Deployments

by Mike Willbanks

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