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* Explain these docs are for trunk (copied from ironic) * All the docs in this repo are meant to be developer docs, so having a devref inside of the docs is redundant and just makes the docs more complicated to navigate. Move everything out of the devref folder and link to everything from main index. * Move man pages into separate section. The man pages are pretty sparse * right now, we should either make them useful or just delete them * Remove dead docs from unused_docs list in doc/source/conf.py * Shuffle docs landing page, move common referees to the top (API, hypervisor support matrix), Add a introduction section and more. The hope is the updated layout makes this document easier to navigate. * Use maxdepth of 1 * Rename a few sections with what are hopefully better names The next step is to prune out outdated documents and further cleanup this page. Change-Id: Iff453e47ccc902a0e72b1a5f6ce1ee939ff3a1a0
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Services, Managers and Drivers
The responsibilities of Services, Managers, and Drivers, can be a bit confusing to people that are new to nova. This document attempts to outline the division of responsibilities to make understanding the system a little bit easier.
Currently, Managers and Drivers are specified by flags and loaded using utils.load_object(). This method allows for them to be implemented as singletons, classes, modules or objects. As long as the path specified by the flag leads to an object (or a callable that returns an object) that responds to getattr, it should work as a manager or driver.
The nova.service Module
nova.service
The nova.manager Module
nova.manager
Implementation-Specific Drivers
A manager will generally load a driver for some of its tasks. The driver is responsible for specific implementation details. Anything running shell commands on a host, or dealing with other non-python code should probably be happening in a driver.
Drivers should minimize touching the database, although it is currently acceptable for implementation specific data. This may be reconsidered at some point.
It usually makes sense to define an Abstract Base Class for the specific driver (i.e. VolumeDriver), to define the methods that a different driver would need to implement.