Apply configuration from cloud metadata.

it turns a cloud-metadata file like this:

{"keystone": {"database": {"host": "127.0.0.1", "user": "keystone", "password": "foobar"}}}

into service config files like this:

[sql]
connection = mysql://keystone:[email protected]/keystone
...other settings...

Just pass it the path to a directory tree of templates:

os-config-applier -t /home/me/my_templates

The template directory structure should mimic a root filesystem, and contain templates for only those files you want configured.

e.g.

~/my_templates$ tree
.
└── etc
    ├── keystone
    │   └── keystone.conf
    └── mysql
        └── mysql.conf

An example tree can be found here.

If a template is executable it will be treated as an executable template. Otherwise, it will be treated as a mustache template.

If you don't need any logic, just some string substitution, use a mustache template.

Metadata settings are accessed with dot ('.') notation:

[sql]
connection = mysql://{{keystone.database.user}}:{{keystone.database.password}@{{keystone.database.host}}/keystone

Configuration requiring logic is expressed in executable templates.

An executable template is a script which accepts configuration as a json string on standard in, and writes a config file to standard out.

The script should exit non-zero if it encounters a problem, so that os-config-applier knows what's up.

The output of the script will be written to the path corresponding to the executable template's path in the template tree.

#!/usr/bin/env ruby
require 'json'
params = JSON.parse STDIN.read
puts "connection = mysql://#{c['keystone']['database']['user']}:#{c['keystone']['database']['password']}@#{c['keystone']['database']['host']}/keystone"

You could even embed mustache in a heredoc, and use that:

#!/usr/bin/env ruby
require 'json'
require 'mustache'
params = JSON.parse STDIN.read

template = <<-eos
[sql]
connection = mysql://{{keystone.database.user}}:{{keystone.database.password}}@{{keystone.database.host}}/keystone

[log]
...
eos

# tweak params here...

puts Mustache.render(template, params)

# install it
sudo pip install -U git+git://github.com/tripleo/os-config-applier.git

# grab example templates
git clone git://github.com/tripleo/openstack-config-templates /tmp/config

# run it
os-config-applier -t /tmp/config/templates/ -m /tmp/config/cfn-init-data.example -o /tmp/config_output