os-collect-config/README.md

cornfig

Apply configuration from cloud metadata.

What does it do?

it turns a cloud-metdata file like this:

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

into service config files like this:

[sql]
connection = mysql://keystone:foobar@127.0.0.1/keystone
...other settings...

But HOW??

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

cornfig /home/me/my_templates

Templates?

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

e.g.

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

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

Moustache Templates

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

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

Executable Templates

An executable template is a script which accepts parameters in environment variables, and writes a config file to standard out.

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

e.g.

#/bin/sh
echo "[sql]"
echo "connection = mysql://$keystone_database_user:$keystone_database_password@$keystone_database_user/keystone"

TODO: the script is passed the path of the metadata file contents on stdin, so you can use a higher-level languages, too:

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