In the days leading up to the v1.5 release, we bid our Icinga API goodbye and usher in a new API and Web concept.
You may ask yourself, what was this API anyway? Indeed, if you weren’t developing or adapting extensions for the new web interface, you wouldn’t have had much contact with this important project component. When Icinga was conceived, one of the main missions was to facilitate the development of addons and plugins. The API provided a set of commonly used request operations, removing the need to write sql-queries and generally a lot of excess code.
All was well till we decided to offer some extra database flexibility. When we added support for Oracle and PostgreSQL on top of MySQL, we also gave our Icinga API team some extra work. With each change, bug fix or new feature, Marius, Michael L and I had to edit the queries for each database back-end separately. This process was not only complicated and error-prone, but also a sign that we needed a more flexible architecture.
As of Icinga 1.5, the external Icinga API will be replaced by an internal database layer Doctrine, and merged into Icinga Web. Much like before, queries will run through this layer between the database (IDOUtils) and the web interface. However, with Doctrine we can use several database back-ends and querying the database is now much easier. In contrast to SQL, its object relational mapper (ORM) uses Doctrine Query Language, so we now have the flexibility minus the code duplication.

Icinga's new architecture - goodbye Icinga API, hello Doctrine

That being said, queries from the old API still exist, thanks to the ‘legacy layer’ which will transform old API queries into this new ORM type. In this way, we maintain compatibility with addons designed for older Icinga versions. The Rest API is also still there as part of Icinga Web, extending on our Doctrine layer with HTTP for addons that require only certain bits of monitoring info.
With the departure of a standalone API, the average Icinga user will barely notice a change, apart from the fact that the configuration has now been moved to the databases.xml. Best of all, every module developer can now easily access the Icinga database without much code overhead– so addon developers get hacking and let us know how you go!
For more information see our Wiki:
Development Guide for Icinga Web
Icinga Database Essentials
Icinga Web REST API