Nugrant

Nugrant is a library to easily handle parameters that need to be injected into an application via different sources (system, user, current, defaults). But foremost, a Vagrant plug-in that will enhance Vagrantfile to allow user specific configuration values.

Supported platforms:

• Vagrant 1.x
• Ruby 1.9.3+

Quick Start

Using Nugrant as a plug-in provides an easy and hierarchical system to manage machine and user specific parameters.

Let's start with an example. You need to distribute among your enterprise a Vagrantfile to start and provision an AWS EC2 instance (or for an open-source project). The aws_access_key and aws_secret_key should be configurable depending on the user running vagrant up.

To achieve this, simply create a file named .vagrantuser that resides in the directory as your Vagrantfile:

aws:
  access_key: "123456"
  secret_key: "abcdef"

In your Vagrantfile, Nugrant will let you access the parameters via the config.user object:

Vagrant.configure("2") do |config|
  ...

  config.vm.provider :aws do |aws, override|
    aws.access_key_id = config.user.aws.access_key
    aws.secret_access_key = config.user.aws.secret_key

    ...
  end
end

You then ignore the .vagrantuser file in your revision control, so each developer as a specific one with their own values. People often commit a .vagrantuser.example file in project's repository as an easy startup for the various parameters that must be filled in, something like:

aws:
  access_key: "<ACCESS_KEY_HERE>"
  secret_key: "<SECRET_KEY_HERE>"

To find where your project .vagrantuser is located, Nugrant uses the directory where the Vagrantfile is located. It achieves this using the same set of rules as Vagrant meaning you can be in a nested directory and parameters will still be fetched correctly.

Moreover, like other similar system, there is a hierarchy of .vagrantuser files that you can leverage:

Name	Location	Priority	Overrides
Defaults	config.user.defaults	4	-
System	$SYSTEM/.vagrantuser	3	Defaults
User	~/.vagrantuser	2	Defaults & System
Project	.vagrantuser	1	Defaults & System & User

The project level directory is always the same as the directory where your Vagrantfile resides and same rules as Vagrant are used to find it. The ~ is the user's home directory and $SYSTEM is the platform dependent folder where system global can be put. Check Hierarchy section for where $SYSTEM maps exactly.

You can use the command vagrant user parameters to see the final merged hierarchy seen by Nugrant. This command also prints restricted keys defined in your hierarchy.

Accessing parameters in your Vagrantfile can be done either by method access (i.e. config.user.<key>) or by array access (i.e. config.user[<key>]). This support is working for any deepness, only config.user is different because provided directly by Vagrant and not by this plugin.

However, a drawback with method access, not present with array access, is its set of restricted keys for which usage is prohibited. These are in facts calls to method defined by the Bag class (Bag extends Hash). It's plain Ruby, use it at your advantage like iterating through a collection using the .each method.

This is where the quick start end. Continue to section Installation if you need so help on how to install Nugrant. Or jump to Usage section which describe in greater details all necessary information needed to deeply understand Nugrant and use it at its full potential.

Installation

Vagrant

Vagrant's plug-in system is very well done and Nugrant supports the following plug-in API versions:

• V2 => Vagrant 1.x

To install the Nugrant as a Vagrant plug-in, simply type the following command in a terminal:

vagrant plugin install nugrant

Vagrant 0.x

Vagrant 0.x is not supported anymore. If you still need support for Vagrant 0.x, please use release line 1.x (branch 1.x).

Library

If you would like to use Nugrant as a library, simply reference it as a dependency of your application. Probably by adding it to your Gemfile or your .gemspec file.

"nugrant", "~> 2.0"

Usage

Whether used as a library or a Vagrant plug-in, Nugrant has some common concepts that apply to both usages. The most important one is the parameters hierarchy.

Common

Nugrant can read parameters from various locations and will merge them all together in a single set. Merging is done in a fairly standard fashion.

Here the precedence rules that apply when merging parameters from various location. List index indicate the priority of the entry. Entry with lower number has lower priority (values at this priority will be overridden by values defined on higher priorities).

1. Defaults
2. System
3. User
4. Current

In text, this means that current parameters overrides user parameters, user parameters overrides system parameters and finally system parameters overrides defaults parameters.

When two keys that are merged together points to Array values, the default operation is to replace current Array by overriding one. The default merge strategy can be customized.

Vagrant

All examples shown here are for Vagrant 1.1+. They have been tested with Vagrant 1.4.0. Keep this in mind when copying examples.

Let start with a small use case. Say the git repository you want to share with your guest VM is not located under the root folder of your Vagrantfile. That means you will need to specify an absolute host path to share the folder on the guest VM.

Your Vagrantfile would look like this:

Vagrant.configure("2") do |config|
  config.vm.box = "base"
  config.vm.synced_folder "/home/user/work/git", "/git"
end

However, what happens when multiple developers need to share the same Vagrantfile? This is the main use case this plug-in try to address.

When Vagrant starts, it loads all vagrant plug-ins it knows about. If you installed the plug-in with one of the two methods we listed above, Vagrant will know about Nugrant and will load it correctly.

To use the plug-in, first create a YAML file named .vagrantuser in the same folder where your Vagrantfile is located. The file must be a valid YAML file:

repository:
  project: "/home/user/work/git"

The configuration hierarchy you define in the .vagrantuser file is imported into the config object of the Vagrantfile under the key user. So, with the .vagrantuser file above, you could have this Vagrantfile that abstract absolute paths.

Vagrant.configure("2") do |config|
  config.vm.box = "base"
  config.vm.synced_folder config.user.repository.project, "/git"
end

This way, paths can be customized by every developer. They just have to add a .vagrantuser file where user specific configuration values can be specified. The .vagrantuser should be ignored by you version control system so it is to committed with the project.

Additionally, you can also have a .vagrantuser under your user home directory. This way, you can set parameters that will be available to all your Vagrantfile'. The .vagrantuserlocated within the same folder as theVagrantfilefile will overrides parameters defined in the.vagrantuser` file defined in the user home directory.

For example, you have .vagrantuser file located at ~/.vagrantuser that has the following content:

ssh_port: 2223
repository:
  project: "/home/user/work/git"

And another .vagrantuser within the same folder as your Vagrantfile:

ssh_port: 3332
repository:
  personal: "/home/user/personal/git"

Then, the Vagrantfile could be defined like this:

Vagrant.configure("2") do |config|
  config.ssh.port config.user.ssh_port

  config.vm.synced_folder config.user.repository.project, "/git"
  config.vm.synced_folder config.user.repository.personal, "/personal"
end

That would be equivalent to:

Vagrant.configure("2") do |config|
  config.ssh.port 3332

  config.vm.synced_folder "/home/user/work/git", "/git"
  config.vm.synced_folder "/home/user/personal/git", "/personal"
end

Hierarchy

As you can see, the parameters defined in the second .vagrantuser file (the current one) overrides settings defined in the .vagrantuser found in the home directory (the user one).

Here the list of locations where Nugrant looks for parameters:

1. Defaults (via config.user.defaults in Vagrantfile)
2. System (/etc/.vagrantuser on Unix, %PROGRAMDATA%/.vagrantuser or %ALLUSERSPROFILE%/.vagrantuser on Windows)
3. Home (~/.vagrantuser)
4. Project (.vagrantuser within the same folder as the Vagrantfile)

Paths

When you want to specify paths on, specially on Windows, it's probably better to only use forward slash (/). The main reason for this is because Ruby, which will be used at the end by Vagrant is able to deal with forward slash even on Windows. This is great because with this, you can avoid values escaping in YAML file. If you need to use backward slash (\), don't forget to properly escape it!

value: "C:/Users/user/work/git"
value: "C:\\Users\\user\\work\\git"

Moreover, it is preferable that paths are specified in full (i.e. no ~ for HOME directory for example). Normally, they should be handled by Vagrant but it may happen that it's not the case. If your have an error with a specific parameter, either expand it in your config:

project: "/home/joe/work/ruby/git"

Of expand it in the Vagrantfile:

config.vm.synced_folder File.expand_path(config.user.repository.project), "/git"

Parameters access

Parameters in the Vagrantfile can be retrieved via method call of array access.

config.user['repository']['project'] # Array access
config.user.repository.project       # Method access

You can even mix the two if you want, but we do not recommend it since its always better to be consistent:

config.user['repository'].project # Mixed access
config.user.repository['project'] # Mixed access

Only the root key, i.e. config.user, cannot be access with both syntax, only the method syntax can be used since this is not provided by this plug-in but by Vagrant itself.

Tips

Each non-final parameter (i.e a parameter that contains other parameters and not a scalar value) is in fact a Bag object. You can call any defined methods on it. This object extends Hash (itself including module Enumerable). Hence, you can do neat things like iterating over your values or filtering them:

config.user.application.users.each do |key, data|
  puts "Key #{key}: #{data}"
end

Restricted keys

Method access has the neat advantage of being beautiful to the eye. However, the drawback of using this retrieval syntax is that not all keys are permitted. As explained in the Tips section, the object you are calling when using method access is in fact of type Bag. Hence, if you are using a key which collapse with ones of Bag's keys, it will call the method instead of given you the value of you parameter. At best, you will get a weird behavior and at worst a stack trace when trying to access the parameter.

If you really want to use one of the restricted keys, simply ensure to always use array access method.

The list of restricted keys can be accessed using command vagrant user restricted-keys.

Default values

When using parameters, it is often needed so set default values for certain parameters so if the user does not define one, the default value will be picked up.

For example, say you want a parameter that will hold the ssh port of the vm. This parameter will be accessible via the parameter config.user.vm.ssh_port.

You can use the following snippet directly within your Vagrantfile to set a default value for this parameter:

Vagrant.configure("2") do |config|
  config.user.defaults = {
    "vm" => {
      "ssh_port" => "3335"
    }
  }

  config.ssh.port config.user.vm.ssh_port
end

With this Vagrantfile, the parameter config.user.vm.ssh_port will default to 3335 in cases where it is not defined by the user.

If the user decides to change it, he just has to set it in his own .vagrantuser and it will override the default value defined in the Vagrantfile.

Array merge strategies

As stated previously, when two arrays are merged together, the default strategy is to replace current array with new one.

However, in some certain circumstances, you may need another behavior. Here the list of strategies that can be used.

• :replace (default) With this strategy, the new array completely replace the current one.

• :concat With this strategy, new array is appended to the end of current array when merged. The Array + operator is used to concatenante the two arrays.

• :extend With this strategy, current array is extended with values from new one. The Array | (union) operator is used to extend the array.

You can use the following snippet directly within your Vagrantfile to change the array merge strategy:

Vagrant.configure("2") do |config|
  config.user.array_merge_strategy = :extend

  config.ssh.port config.user.vm.ssh_port
end

Note that you should change the array merge strategy before you access any keys because it's just once set that values are computed using the new strategy.

If you specify an unsupported strategy, nothing will happen.

Commands

In this section, we describe the various vagrant commands defined by this plug-in that can be used to interact with it.

Parameters

This command will print the currently defined parameters at the given location. All rules are respected when using this command. It is usefull to see what parameters are available and what are the current values of those parameters.

Usage:

> vagrant user parameters
---
config:
  user:
    chef:
      cookbooks_path: /Users/Chef/kitchen/cookbooks
      nodes_path: /Users/Chef/kitchen/nodes
      roles_path: /Users/Chef/kitchen/roles

Add flag -h (or --help) for description of the command and a list of available options.

Restricted Keys

This command will print the keys that cannot be accessed using the method access syntax.

Usage:

> vagrant user restricted-keys

Env

Sometimes, you would like to have acces to the different values stored in your .vagrantuser from environment variables. This command is meant is exactly for this.

By using one of the three methods below, you will be able to export (but also unset) environment variables from your current parameters as seen by Nugrant.

You can see the commands that will be executed by simply calling the method:

vagrant user env

The name of the environment will be upper cased and full path of the key, without the config.user prefix, separated with _. For example, the key accessible using config.user.db.user and with value root would generate the export command:

export DB_USER=root

And the unset command:

unset DB_USER

The value are escaped so it is possible to define value containing spaces for example.

A last note about generate commands is that pre-existing environment variable are not taking in consideration by this command. So if an environment variable with name DB_USER already exist, it would be overwritten by an export command.

Add flag -h (or --help) for description of the command and a list of available options.

Method #1

If you plan to use frequently this feature, our best suggestion is to create a little bash script that will simply delegates to the real command. By having a bash script that calls the command, you will be able to easily export environment variables by sourcing the script.

Create a file named nugrant2env somewhere accessible from the $PATH variable with the following content:

#!/bin/env sh

$(vagrant user env "$@")

This script will simply delegates to the vagrant user env command and pass all arguments it receives to it. The magic happens because the command vagrant user env outputs the various export commands to the standard output.

By sourcing the simple delegating bash script, the parameters seen by Nugrant will be available in your environment:

. nugrant2env

By default, export commands are generated. But you can pass some options to the nugrant2env script, For example, to generate the unset ones, add --unset (or simply -u).

. nugrant2env --unset

For a list of options, see the help of the command delegated to:

vagrant user env -h

Method #2

Use the command to generate a base script in the current directory that you will then source:

vagrant user env --format script

This will generate a script called nugrant2env.sh into the current directory. You then simply source this script:

. nugrant2env.sh

Using vagrant user env -u --format script will instead generate the bash script that will unset the environment variables. Don't forget to source it to unset variables.

Method #3

Use the command to generate an autoenv file in the current directory. By using the [autoenv] project, anytime you will enter the project directory via the cd command, variables exported found in the .env file generated will be exported to your environment.

vagrant user env --format autoenv

This will generate a file called .env in the current directory. You then simply change to the directory where the .env file was generated to made exported variables available in your environment.

cd ..
cd <project_dir>

Using vagrant user env -u --format autoenv will instead generate the autoenv file that will unset the environment variables.

Automatic Env file

Sometimes, you prefer generate the env file automatically before each provision.

The following configuration option generate the [autoenv] file

config.user.auto_export = :env

The following configuration option generate a base script

config.user.auto_export_script_path = "./script/env.sh" # optional, default "./nugrant2env.sh"
config.user.auto_export = :script

To export on same time :script and :env use the following

config.user.auto_export = [:script, :env]

Library

Using Nugrant as a library to handle parameters from various location is really easy. Two main classes need to be handled.

First, you need to create a Nugrant::Config object. This configuration holds the values that needs to be customized by your own application. This includes the different parameters paths and the format of the parameters file.

Contributing

You can contribute by filling issues when something goes wrong or was not what you expected. I will do my best to fix the issue either in the code or in the documentation, where applicable.

You can also send pull requests for any feature or improvement you think should be included in this plug-in. I will evaluate each of them and merge them as fast as possible.