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Graffiti Architecture

Base Concepts

    • Various OpenStack services provide techniques to abstract low level resource selection to one level higher, such as flavors, volume types, or artifact types. These resource abstractions often allow "metadata" in terms of key-value pair properties to further specialize and describe instances of each resource type. However, collaborating on those properties is largely a disconnected and difficult process. This often involves searching outdated wikis and opening the source code. It becomes more difficult as a cloud's scale grows. In addition, many times the properties can apply to resources from several different services. Graffiti makes this easier by creating the following concepts:
      • Capabilities and Requirements: Graffiti embraces the idea that cloud resources may be described using capabilities and requirements, a concept influenced by some parts of OpenStack today as well as by industry specifications like OASIS TOSCA (Please note, Graffiti is NOT an orchestration engine, it only assists in describing and locating existing resources in the cloud.).
      • Dictionary: A common API for services, admins, and users to discover and share their metadata vocabulary. This is the basis for creating an agreement on how to describe the various capabilities the cloud provides. It supports both unstructured properties and structured / hierarchical metadata in the form of "capability types".
      • Directory: A common API to "tag" and search across existing and new services for cloud content based on the metadata vocabulary, ad-hoc properties, or freeform text.
      • Resource Capability Registry: A persistent shared repository for services to publish information about cloud resources. This can optionally be used by services instead of or in addition to having their own local native storage to describe resources.

Graffiti provides cross service "metadata tagging" and search aggregation for cloud resources. In Graffiti, metadata definitions may be simple property types or may be structured into simple hierarchy of objects that we call capabilities.

Graffiti provides cross service and cross environment:

  • metadata definition aggregation and administration
  • resource "tagging" aggregation
  • resource metadata search aggregation

Worklow / Component Concepts

  1. Load your metadata definitions (called property types or capability types) into the Graffiti central dictionary or configure Graffiti to include existing definitions provided by the various services
  2. "Tag" the resources in the cloud with your properties and capabilities
  3. Let end users and admins find the resources with your desired properties and capabilities


Proposed Horizon Widgets

In Graffiti, we are proposing reusable widgets that we will plug into Horizon. The widgets will provide the ability to "tag" capabilities and requirements on various resources. They will also be able to generate filter criteria that a Graffiti plugin service can use to filter resources.


Proposed Horizon Component Architecture

We would like there to be a common way in Horizon to support "tagging" key-value pairs. In our architecture, we will support Horizon gaining the value of Graffiti concepts through a thin API plugin layer without the full Graffiti service. This will provide benefits now, without requiring Graffiti to either be incubated or be adopted into other projects (which we are actively seeking input and advice).

The entire concept can be run in a lightweight way through a thin filesystem provider on the Horizon server that allows reading dictionary definition files directly from the filesystem. This would suffice for single node deployments or deployments that are managed through configuration management provider to ensure consistency of the definitions across Horizon nodes.

When the full Graffiti API service is available, the widgets don't change. They still go to the Graffiti Horizon API, which then swaps the plugin to talk to the Graffiti service. When the Graffiti service in integrated into the ecosystem the following additional benefits will be available:

  • Command line and REST API for cross service tagging / searching
  • External Persistence for multi-node / HA deployments
  • Resource look-up optimizations
  • Authoring - We will provide an authoring and administration UI for creating and managing namespaces, capability types, etc