Managing Environments with Git

Branches are a way of keeping several different tracks of development within a single source repository. Puppet environments are a lot like Git branches. You can have the same code with slight variations between branches, just as you can have different modules for different environments. In this section, we'll show how to use Git branches to define environments on the Puppet master.

Getting ready

In the previous section, we created a production directory that was based on the master branch; we'll remove that directory now:

puppet@puppet:/etc/puppet/environments$ mv production production.master

How to do it...

Modify the post-receive hook to accept a branch variable. The hook will use this variable to create a directory on the Puppet master as follows:

#!/bin/sh

read oldrev newrev refname
branch=${refname#*\/*\/}

git push puppetmaster $branch
ssh puppet@puppet.example.com "if [ ! -d 
/etc/puppet/environments/$branch ]; then git clone
 /etc/puppet/environments/puppet.git
 /etc/puppet/environments/$branch; fi; cd
 /etc/puppet/environments/$branch; git checkout $branch; git pull"

Modify your README file again and push to the repository on git.example.com:

t@mylaptop puppet$ git add README
t@mylaptop puppet$ git commit -m "Adding README"
[master 539d9f8] Adding README
 1 file changed, 1 insertion(+)
t@mylaptop puppet$ git push
Counting objects: 5, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 374 bytes | 0 bytes/s, done.
Total 3 (delta 1), reused 0 (delta 0)
remote: To puppet@puppet.example.com:/etc/puppet/environments/puppet.git
remote: 0d6b49f..539d9f8 master -> master
remote: Cloning into '/etc/puppet/environments/master'...
remote: done.
remote: Already on 'master'
remote: Already up-to-date.
To git@git.example.com:repos/puppet.git
 0d6b49f..539d9f8 master -> master

How it works...

The hook now reads in the refname and parses out the branch that is being updated. We use that branch variable to clone the repository into a new directory and check out the branch.

There's more...

Now when we want to create a new environment, we can create a new branch in the Git repository. The branch will create a directory on the Puppet master. Each branch of the Git repository represents an environment on the Puppet master:

1. Create the production branch as shown in the following command line:

   t@mylaptop puppet$ git branch production
   t@mylaptop puppet$ git checkout production
   Switched to branch 'production'
   

2. Update the production branch and push to the Git server as follows:

   t@mylaptop puppet$ vim README
   t@mylaptop puppet$ git add README
   t@mylaptop puppet$ git commit -m "Production Branch"
   t@mylaptop puppet$ git push origin production
   Counting objects: 7, done.
   Delta compression using up to 4 threads.
   Compressing objects: 100% (3/3), done.
   Writing objects: 100% (3/3), 372 bytes | 0 bytes/s, done.
   Total 3 (delta 1), reused 0 (delta 0)
   remote: To puppet@puppet.example.com:/etc/puppet/environments/puppet.git
   remote: 11db6e5..832f6a9 production -> production
   remote: Cloning into '/etc/puppet/environments/production'...
   remote: done.
   remote: Switched to a new branch 'production'
   remote: Branch production set up to track remote branch production from origin.
   remote: Already up-to-date.
   To git@git.example.com:repos/puppet.git
    11db6e5..832f6a9 production -> production
   

Now whenever we create a new branch, a corresponding directory is created in our environment's directory. A one-to-one mapping is established between environments and branches.