During the Essex release cycle, Horizon underwent a significant set of internal changes to allow extensibility and customization while also adding a significant number of new features and bringing much greater stability to every interaction with the underlying components.
Making Horizon extensible for third-party developers was one of the core goals for the Essex release cycle. Massive strides have been made to allow for the addition of new “plug-in” components and customization of OpenStack Dashboard deployments.
To support this extensability, all the components used to build on Horizon’s interface are now modular and reusable. Horizon’s own dashboards use these components, and they have all been built with third-party developers in mind. Some of the main components are listed below.
Horizon’s structure has been divided into logical groupings called dashboards and panels. Horizon’s classes representing these concepts handle all the structural concerns associated with building a complete user interface (navigation, access control, url structure, etc.).
One of the most common activities in a dashboard user interface is simply displaying a list of resources or data and allowing the user to take actions on that data. To this end, Horizon abstracted the commonalities of this task into a reusable set of classes which allow developers to programmatically create displays and interactions for their data with minimal effort and zero boilerplate.
Support for Nova’s features has been greatly improved in Essex:
Support for managing Floating IP address pools.
New instance and volume detail views.
A new “Settings” area was added that offers several userful functions:
Internationalization fully enabled, with all strings marked for translation.
Client-side templating capabilities for more easily creating dynamic interactions.
Frontend overhaul to use the Bootstrap CSS/JS framework.
Centralized error handling for vastly improved stability/reliability across APIs/clients.
Completely revamped test suite with comprehensive test data.
Forward-compatibility with Django 1.4 and the option of cookie-based sessions.
Quantum support has been removed from Horizon for the Essex release. It will be restored in Folsom in conjunction with Quantum’s first release as a core OpenStack project.
Due to the mechanisms by which Keystone determines “admin”-ness for a user, an admin user interacting with the “Project” dashboard may see some inconsistent behavior such as all resources being listed instead of only those belonging to that project, or only being able to return to the “Admin” dashboard while accessing certain projects.
Exceptions raised while overriding built-in Horizon behavior via the “customization_module” setting may trigger a bug in the error handling which will mask the original exception.
The Essex Horizon release is only partially backwards-compatible with Diablo OpenStack components. While it is largely possible to log in and interact, many functions in Nova, Glance and Keystone changed too substantially in Essex to maintain full compatibliity.