Continuous Integration with Fabric

Continuous Integration
With Fabric
http://docs.fabfile.org

Varun Batra @ Deft Infotech Pvt. Ltd.

I am Lazy!
I need one command to deploy codes.
>fab deploy
That’s what I was talking about 


What if something goes wrong?
>fab deploy
This command should handle that as well and report me.


Common Principle of CI
• Code Repository (I use GIT)
• Fast & Auto Build
• Self Testing
• ‘Test Environment’ is not ‘Build Environment’
• Auto Deployment: merge to master/deploy branch (GIT), this should
auto deploy it
• Self Sustainable System, e.g. if db is destroyed, it should automatically
recreated by latest backup


My Deployment Principle
• Based on my experience
• Based on guys’s ‘better than me’ experience
• Let me know if you can improve because you can


Why Fabric?
I learned it in half day
It can do what I need
Few seconds installation


GIT
>git branch something_cool
>git checkout something_cool
>git commit -a -m ‘what I did?’
>git checkout master
>git merge something_cool
>git push
git checkout -b something_cool combines first two commands

Fabric: library + command-line tool
Fabric is a Python (2.5 or higher) library and command-line tool for
streamlining the use of SSH for application deployment or systems
administration tasks.
I copied from their website, I am lazy


Fabric Features
• Runs local and remote commands
• Runs normal or sudo commands
• Upload & Download files
• Prompt for input
• Simultaneous deploying in multiple server
• Output in different colors like red(text,bold=False)


Fabric combines

fabfile.py

fab


There is a catch
each run or sudo call has its own distinct shell session.
run('cd foo' && 'mkdir bar')
is not
run('cd foo')
run('mkdir bar')
is
with('cd foo')
run('mkdir bar')


How discussed deployment process should
be?


Processing Output
Output of ‘run’ command is stored in ‘url’ variable


Deploy with options?
• Passing parameters?
• fab deploy:env=production
• fab deploy:production (in order of params)
• !Passing True is string i.e. ‘True’ not True

• Deploy to many hosts?
• env.hosts = ['user@example1.com', ' user@example2.com ']
• fab –H user@example1.com, user@example2.com deploy

• Show fewer output?
• with hide('output','running'), settings(warn_only=True):


@serial VS @parallel


More decorators?
• @hosts
• @roles
• @runs_once !caution with @parallel
• @task
• @with_settings
• @serial
• @parallel


Context Managers
Remember ‘with’?

with('cd ~/git_repo/'):
run('git pull')
#cd ~/git_repo/ && git pull
with hide('running', 'stdout', 'stderr'):
do_something()

Context Manager cont’d..
• cd
• with
• lcd
• path
• prefix
• settings
• show


Contributions
• File/directory management
• comment/uncomment, sed, append, contains, exists, upload_template, first

• Project Tools
• rsync_project, upload_project

• Django integration


Lets look at fabfile.py


But wait..
What about autodeployment?
cron VS service


fab prompt_for_any_questions

fab stay_in_touch

Varun Batra
IT Consultant
Deft Infotech Pvt. Ltd.
skype:varunb.deftinfotech
http://varunbatra.com
CodeVarun@gmail.com
https://www.linkedin.com/in/varunbatra/
https://www.facebook.com/VarunBatraIT
https://twitter.com/batravarun


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