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Blueprint Structure

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Remember the Python web server application you have just deployed?

Let’s see how it’s structured.

The blueprint contains a blueprint.yaml file which describes our application stack; two scripts which install and uninstall the application and some application related files.

The scripts and application related files are not so interesting right now. What is interesting is the blueprint.yaml file.

This is our blueprint.yaml file:

  
tosca_definitions_version: cloudify_dsl_1_3


imports:
  - http://www.getcloudify.org/spec/cloudify/3.4/types.yaml


inputs:
  webserver_port:
    description: >
      The HTTP web server port.
    default: 8000

  host_ip:
    default: localhost


node_templates:
  host:
    type: cloudify.nodes.Compute
    properties:
      ip: { get_input: host_ip }
      install_agent: false

  http_web_server:
    type: cloudify.nodes.WebServer
    properties:
      port: { get_input: webserver_port }
    relationships:
      - type: cloudify.relationships.contained_in
        target: host
    interfaces:
      cloudify.interfaces.lifecycle:
        create: install.py
        delete: uninstall.py


outputs:
  http_endpoint:
    description: Web server external endpoint
    value: { concat: ['http://', { get_property: [ host, ip ] },
                      ':', { get_property: [http_web_server, port] }] }
  

You can see that our blueprint has a tosca_definitions_version, and imports, inputs, node_templates and outputs sections.

• The tosca_definitions_version is the version of the blueprint’s DSL (Domain Specific Language).
• imports is where you import additional yaml files to use in your blueprint.
• inputs are somewhat like the blueprint’s configuration. You can set different inputs and use them across the blueprint.
• node_templates contains your application’s resources and how they’re deployed.
• outputs are pieces of information you can use after a blueprint was deployed.

There are additional sections which you can use, but we’ll ignore them for now.

So what did we do here? Let’s break this down

We defined two inputs: the machine’s IP (in this case, we’re running on our local machine so it’s localhost.); and the port we’d like the server to be served on.

  
inputs:
  webserver_port:
    description: >
      The HTTP web server port.
    default: 8000

  host_ip:
    default: localhost
  

We defined node_templates, which contain two resources: a host node (our local machine) and an http_web_server node. The type of these resources are inherited from the file we imported in the imports section. We’ll ignore that for now.

Properties are resource level configuration options. Our host contains an ip property, which gets its value from one of our inputs using a built-in function called get_input.

We’re not installing any agents here, so you can ignore install_agent.

  
node_templates:
  host:
    type: cloudify.nodes.Compute
    properties:
      ip: { get_input: host_ip }
      install_agent: false

  ...
  

We defined a port property of our http_web_server resource, which gets its value from the other input.

We used a relationship to state that the http_web_server is contained in the host and declared the relevant scripts - install.py and uninstall.py to be executed when installing and uninstalling the application. The install.py and uninstall.py files, as well as the Cloudify logo are resources provided alongside the blueprint.

You’ve seen the instances of these node_templates during the Quickstart when running cfy local instances.

  
node_templates:
  ...

  http_web_server:
    type: cloudify.nodes.WebServer
    properties:
      port: { get_input: webserver_port }
    relationships:
      - type: cloudify.relationships.contained_in
        target: host
    interfaces:
      cloudify.interfaces.lifecycle:
        create: install.py
        delete: uninstall.py

  

Lastly, we defined an output, which provides us with the endpoint of our server. You’ve seen this output during the Quickstart when running cfy local outputs.

  

outputs:
  http_endpoint:
    description: Web server external endpoint
    value: { concat: ['http://', { get_property: [ host, ip ] },
                      ':', { get_property: [http_web_server, port] }] }
  

What’s Next

If you want to learn more about blueprints, you can head off to the blueprints section.