Node Types


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 may 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, one can build various type hierarchies which can be reused over different application blueprints.

When a type derives from another type, its interfaces and properties keys get 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 will be overridden by a property with the same name defined on the deriving type. The same is true for an interface operation mapping - however, it is important to note that it’s possible to add in the deriving type additional operation mappings to an interface defined in the parent type. See the examples section for more on this.

Note

When not deriving from any other type, it’s good practice to derive from the cloudify.types.Root type defined in the Cloudify built-in types.

Not doing so will require either writing custom workflows or declaring the cloudify.interfaces.lifecycle interface in this new type, since the built-in install and uninstall workflows are based on interfaces declared for the cloudify.types.Root type.

interfaces

The interfaces property may be used to define common behaviors for node templates. See more over at the Interfaces documentation.

properties

The properties property may 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 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)

Built-in Node Types

Cloudify provides some built-in node types, you can check them out here.

Examples

The 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 will now have both the port property and the three operations defined for the nodecellar.nodes.MongoDatabase type.

Finally, an example on 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 which was defined in the previous example; As such, it derives its properties and interfaces definitions, which get either merged or overridden by the ones it defines itself.

A node template whose type is nodecellar.nodes.MongoDatabaseExtended will therefore have both the port and enable_replication properties, as well as 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 it is evident, the configure operation, which is mapped only in the extending type, got merged with the start and stop operations which are only mapped in the parent type, while the create operation, which is defined on both types, will be mapped to the value set in the extending type.