Node Types

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node_types are used for defining common properties and behaviors for node-templates. node-templates can then be created based on these types, inheriting their definitions.

Declaration

node_types:

  type1:
    derived_from: cloudify.types.Root
    interfaces:
      ...
    properties:
      ...

  type2:
    ...
  ...

Schema

Keyname	Required	Type	Description
derived_from	no	string	A string referencing a parent type.
interfaces	no	dictionary	A dictionary of node interfaces.
properties	no	dictionary	A dictionary of node properties.

derived_from

The derived_from property can be used to build over and extend an existing type. This is useful for further extracting common properties and behaviors, this time in between types.

Using this mechanism, you can build various type hierarchies that can be reused across different application blueprints.

When a type derives from another type, its interfaces and properties keys are merged with the parent type’s interfaces and properties keys. The merge is on the property/operation level. A property defined on the parent type is overridden by a property with the same name that is defined on the deriving type. The same is true for an interface operation mapping. However, it is important to note that it is possible to add additional operation mappings to an interface defined in the parent type in the deriving type. See the examples section for more information.

interfaces

The interfaces property can be used to define common behaviors for node templates. For additonal information, see the Interfaces documentation.

properties

The properties property can be used to define a common properties schema for node templates.

properties is a dictionary from a property name to a dictionary describing the property. The nested dictionary includes the following keys:

Keyname	Required	Type	Description
description	no	string	Description for the property.
type	no	string	Property type. Not specifying a data type means the type can be anything (including types not listed in the valid types). Valid types: `string`, `integer`, `float`, `boolean`, `list`, `dict`, `regex` or a custom data type.
default	no	<any>	An optional default value for the property.
required	no	boolean	Specifies whether the property is required. (Default: `true`, Supported since: cloudify_dsl_1_2)

Examples

Following is an example node type definition extracted from the Cloudify-Nodecellar-Example blueprint.

node_types:
  nodecellar.nodes.MongoDatabase:
    derived_from: cloudify.nodes.DBMS
    properties:
      port:
        description: MongoDB port
        type: integer
    interfaces:
      cloudify.interfaces.lifecycle:
        create: scripts/mongo/install-mongo.sh
        start: scripts/mongo/start-mongo.sh
        stop: scripts/mongo/stop-mongo.sh

An example of how to use this type follows:

node_templates:
  MongoDB1:
    type: nodecellar.nodes.MongoDatabase
  MongoDB2:
    type: nodecellar.nodes.MongoDatabase

Each of these two nodes now have both the port property and the three operations defined for the nodecellar.nodes.MongoDatabase type.

Finally, here is an example of how to extend an existing type by deriving from it.

node_types:
  nodecellar.nodes.MongoDatabaseExtended:
    derived_from: nodecellar.nodes.MongoDatabase
    properties:
      enable_replication:
        description: MongoDB replication enabling flag
        type: boolean
        default: false
    interfaces:
      cloudify.interfaces.lifecycle:
        create: scripts/mongo/install-mongo-extended.sh
        configure: scripts/mongo/configure-mongo-extended.sh

The nodecellar.nodes.MongoDatabaseExtended type derives from the nodecellar.nodes.MongoDatabase type that was defined in the previous example. As such, it derives its properties and interfaces definitions, which are either merged or overridden by the ones it defines itself.

A node template with a nodecellar.nodes.MongoDatabaseExtended type therefore has both the port and enable_replication properties, and the following interfaces mapping:

    interfaces:
      cloudify.interfaces.lifecycle:
        create: scripts/mongo/install-mongo-extended.sh
        configure: scripts/mongo/configure-mongo-extended.sh
        start: scripts/mongo/start-mongo.sh
        stop: scripts/mongo/stop-mongo.sh

As is evident, the configure operation, which is mapped only in the extending type, merged with the start and stop operations that are only mapped in the parent type, whereas the create operation, which is defined on both types, is mapped to the value set in the extending type.