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.
node_types: type1: derived_from: cloudify.types.Root interfaces: ... properties: ... type2: ... ...
|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 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
properties keys are merged with the parent type’s
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.
When not deriving from any other type, it is good practice to derive from the
cloudify.types.Root type that is defined in the built-in types. If you do not do this, you must either write a custom workflow or declare the
cloudify.interfaces.lifecycle interface in this new type. This is required because the built-in install and uninstall workflows are based on interfaces that are declared for the
interfaces property can be used to define common behaviors for node templates. For additonal information, see the Interfaces documentation.
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:
|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:
|default||no||<any>||An optional default value for the property.|
|required||no||boolean||Specifies whether the property is required. (Default:
Cloudify provides some built-in node types, which you can find out about here.
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
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
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
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
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.