Technical Reference Deep Dives¶
The nova project is large, and there are lots of complicated parts in it where it helps to have an overview to understand how the internals of a particular part work.
Internals¶
The following is a dive into some of the internals in nova.
AMQP and Nova: How nova uses AMQP as an RPC transport
Scheduling: The workflow through the scheduling process
Scheduler hints versus flavor extra specs: The similarities and differences between flavor extra specs and scheduler hints.
Live Migration: The live migration flow
Services, Managers and Drivers: Module descriptions for some of the key modules used in starting / running services
Virtual Machine States and Transitions: Cheat sheet for understanding the life cycle of compute instances
Threading model: The concurrency model used in nova, which is based on eventlet, and may not be familiar to everyone.
Notifications in Nova: How the notifications subsystem works in nova, and considerations when adding notifications.
ComputeDriver.update_provider_tree: A detailed explanation of the
ComputeDriver.update_provider_treemethod.Upgrade checks: A guide to writing automated upgrade checks.
Database migrations: A guide to writing database migrations, be they online or offline.
Todo
Need something about versioned objects and how they fit in with conductor as an object backporter during upgrades.
Filtering hosts by isolating aggregates: Describes how the placement filter works in nova to isolate groups of hosts.
Attaching Volumes: Describes the attach volume flow, using the libvirt virt driver as an example.
Driver BDM Data Structures: Block Device Data Structures
Libvirt virt driver OS distribution support matrix: Libvirt virt driver OS distribution support matrix
Debugging¶
Guru Meditation Reports: Inspired by Amiga, a way to trigger a very comprehensive dump of a running service for deep debugging.
Forward Looking Plans¶
The following section includes documents that describe the overall plan behind groups of nova-specs. Most of these cover items relating to the evolution of various parts of nova’s architecture. Once the work is complete, these documents will move into the “Internals” section.
If you want to get involved in shaping the future of nova’s architecture, these are a great place to start reading up on the current plans.
Cells: How cells v2 is evolving
REST API Policy Enforcement: How we want policy checks on API actions to work in the future
Nova Stable REST API: What stable api means to nova
Scheduler Evolution: Motivation behind the scheduler / placement evolution
Additional Information¶
Glossary: A quick reference guide to some of the terms you might encounter working on or using nova.
