API

The runtime model of the system can be manipulated in both imperative and declarative ways. It can be modified through a set of instructions (e.g. instantiate/destroy a node of a predefined type), or a new model can be provided to replace the instantiated one. The latter can be an in memory model or defined in a file (for instance in JSON or XMI) through the MODACloudML’s serialization codecs.

The runtime model is based on the type-instance pattern and consists of two main kinds of elements, namely the node and the artefacts. A node represents a virtual machine (e.g., a virtual machine running GNU/Linux with 2 cores and 2GiB of memory). An artefact represents a software component of the application (e.g., a Java servlet, a Jetty container, or a MongoDB database).

Moreover bindings can be specified between artefacts ports representing either deployment dependencies (e.g., the Jetty container and the MongoDB database have to be deployed before the Java servlet) or communication channels (e.g., a Java servlet communicates with another Java servlet through Hypertext Transfer Protocol Secure - HTTPS - on port 443).

Accordingly, the models@runtime will provide the following interfaces

##Actions on Types

Command	description
listOfTypes(): List	return the list of types in the current deploymentModel
listOfNodeTypes(): List	return the list of node types in the current deploymentModel
listOfArtefactTypes(): List	return the list of artefact types in the current deploymentModel
listOfBindingTypes(): List	return the list of binding types in the current deploymentModel
getNodeType(String id): NodeType	return information about the type of node with the specified id
getArtefactType(String id): ArtefactType	return information about the type of artefact with the specified id
getBindingType(String id): BindingType	return information about the type of binding with the specified id

##Actions on instances

Command	description
instantiateNode(NodeType type,String name): Node	instantiate a node of type ’type’ in the deployment model
instantiateArtefact(ArtefactType type, String name): Artefact	instantiate an artefact of type ’type’ in the deployment model
instantiateBinding(String artefactPortId,String artefactPortId):Binding	instantiate a binding between two artefacts ports. Depending on the type of port used as parameter, the created binding can depict a communication channel (describe how the two artefacts will communicate) or a deployment dependency (An artefact require another artefact to run properly)
removeNode(String id): Boolean	remove the node instance with the specified id from the deployment model
removeArtefact(String id): void	remove the artefact instance with the specified id from the deployment model
removeBinding(String id): void	remove the binding instance with the specified id from the deployment model
setProvider(NodeInstance node,Provider p): void	define the cloud provider on which the node instance should be provisioned
setDestination(String artefactId,String nodeId): void	define the node on which the artefact should be deployed
listOfInstances(): List	return the list of instances in the current deployment Model
listOfNodes(): List	return the list of node instances in the current deploymentModel
listOfArtefacts(): List	return the list of artefact instances in the current deploymentModel
listOfBindings(): List	return the list of binding instances in the current deploymentModel
getArtefact(String id): Artefact	return information about the artefact with the specified id
getNode(String id): Node	return information about the node with the specified id
getBinding(String id): Binding	return information about the binding with the specified id

##Declarative approach

Command	description
getDeploymentModel()	return the current deploymentModel
loadDeploymentModel(deploymentModel)	load a deployment model as the current deploymentModel
saveDeploymentModel(deploymentModel)	save the current deploymentModel

##Lifecycle commands In addition the models@runtime engine of CloudML will provide the following interface to manage the lyfe cycles of node and artefact instances.

Command	description
stopArtefact(String artefactId): Artefact	stop the specified artefact
installArtefact(String artefactId): Artefact	install the artefact with the specified id
configureArtefact(String artefactId): Artefact	configure the artefact with the specified id
startArtefact(String artefactId): Artefact	start the artefact with the specified id
uninstallArtefact(String artefactId): Artefact	delete the virtual machine instance with the specified id
provisionNode(String nodeId): Node	create an instance of a virtual machine with the specified startNode(String nodeId): Node
stopNode(String nodeId): Node	shut-down a virtual machine (data persists) with the specified terminateNode(String nodeId): void
scaleOut(String nodeId, Integer instanceNumber): void	create n new node instances of the same type.
scaleIn(String nodeId, Integer instanceNumber): void	delete n node instances