Roboconf DSL

Here is a summary of Roboconf’s DSL and keywords.
Let’s start with graph(s) definitions.

The graph(s) is a set of graphs.
It is made up of roots components. A component can have several children, and several parents. A graph(s) must have at least one root component. Several root components indicate several entry points to walk through the graph(s).

Components

A component is defined as follows:

MyComp {
	...
}

It is a name followed by an opening curly bracket.
Component properties must be defined from the next line, one property per line.

Here are the supported properties for a component.

Property	Description	Required
installer	The installer name, that is to say, which Roboconf extension will handle the life cycle of this component instances.	yes
children	A list of component names, separated by a comma. As an example, an Apache component being a child of a VM component means we could deploy Apache on a VM.	no
exports	A list of exported variables, separated by a comma. Network properties are set dynamically by Roboconf. Others (e.g. a port) must have a default value. For readability purpose, this keyword can appear more than once for a Roboconf component.	no
imports	A list of imported variables, separated by a comma. It means this component will need dependencies to be started. An import can be marked as optional. An import can also be marked as external (see this page for more details). For readability purpose, the imports keyword can appear more than once for a Roboconf component.	no
facets	Some properties can be grouped together in facets. So, this is a list of facet names, separated by a comma.	no
extends	The name of a component this component extends. All its properties and recipes will be inherited.	no

Here is a commented example of a component (without any facet).

ApacheServer {
	# Apache instances will be deployed by Roboconf's Puppet extension
	installer: puppet;

	# Web applications could be deployed over this Apache server
	children: My-Dash-Board, Marketing-Suite;

	# Properties exported by this component.
	# 'port' should have a default value, or we will have to set it when we create an instance.
	exports: port = 19099;
	
	# 'ip' is a special variable. It will be updated at runtime by a Roboconf agent.
	exports: ip;

	# Other components properties that this server needs to have so that it can start.
	imports: LB.port (optional), LB.ip (optional);

	# Here, the Apache may also be notified about components instances of type LB.
	# The imports are marked as optional. It means that if there is no LB instance, an
	# Apache instance will be able to start anyway. 
	#
	# If the import was not optional, e.g.
	#
	# imports: LB.port, LB.ip;
	# or even
	# imports: LB.port (optional), LB.ip;
	# 
	# ... then an Apache instance would need at least one LB instance somewhere.
	
	# Imports may also reference variables from other applications
	imports: external Lamp.lb-ip;
}

Notice that exported variables are prefixed by the component (or the facet) name that defined them.
As an example, if a component Tomcat exports port and ip, and that another component wants to import them, it will need to import Tomcat.port and Tomcat.ip. Same thing if the variables are exported by a facet.

For more information about external imports, read this page.

Facets

Facets are defined in graph(s) definitions.
A facet is an abstract component, meaning it does not have anything related with recipes.
It only supports exports and children properties.

Here is an example of facet.

facet LoadBalanced {
	exports: ip, port;	# Define we export two variables.
}

It starts with the facet keyword, followed by the facet name and an opening curly bracket.
Facets properties must be defined from the next line, one property per line.

Here are the supported properties for a facet.

Property	Description	Required
children	A list of component names, separated by a comma. As an example, an Apache component being a child of a VM component means we could deploy Apache on a VM.	no
exports	A list of exported variables, separated by a comma. Network properties are set dynamically by Roboconf. Others (e.g. a port) must have a default value. For readability purpose, this keyword can appear more than once for a Roboconf component.	no
extends	A facet may extend other facets. So, this is a list of facet names, separated by a comma.	no

Unlike components, facets do not have a resource directory.

Instances

We have seen graph(s) definitions. Let’s continue with instances definitions.
Instances reference components an may override the value of exported properties. They cannot add or remove properties (neither exported, nor imported). They must be compliant with their component definition.

An instance is defined as follows:

instance of MyComp {
	name: MyInstance1;
	...
}

It starts with the instance of keyword, followed by a component name and an opening curly bracket.
Instance properties must be defined from the next line, one property per line.

Here are the supported properties for an instance.

Property	Description	Required
name	The instance name. It supports spaces.	yes
count	The number of instances to create. If not set, it is assumed to be 1.	no
channels	Channels are used to adjust the target of messaging in Roboconf (this feature is not yet back in the code).	no
instance-data	Instance data. This is not expected to be set by hand. But you may encounter it.	no
instance-state	The instance state. This is not expected to be set by hand. But you may encounter it.	no

Instances can be defined hierarchically.
Here is an example.

instance of VM {

	# This will create 5 VM instances, called VM 1, VM 2, VM3, VM 4 and VM 5.
	name: VM ;	# Yes, there is a space at the end... :)
	count: 5;

	# On every VM instance, we will deploy...
	instance of Tomcat {
		name: Tomcat;
	}
}

Instances can also override properties from their component.
Assuming the Tomcat component specified…

Tomcat {
	exports: ip, port = 8080;
}

… a Tomcat instance may override the port value.

instance of Tomcat {
	name: Tomcat;
	port: 11000;
}

It may also define properties that were not defined in the component.
This can be useful sometimes to pass specific data in a script or a Puppet module.

instance of Tomcat {
	name: Tomcat;
	port: 11000;
	checked: true;
}