This document discusses how to extend the Nova cloud computing management framework in OpenStack. It describes adding new resources, properties, and actions through API extensions. It also covers creating custom services that interface with the Nova database and messaging system. The document provides an example of extending Nova to add snapshot and launch capabilities for virtual machines using Gridcentric's proprietary code.

1. Extending
for Fun and Profit
Tim Smith – Co-founder, Gridcentric

2. A bit about me
 Co-founder & President of Gridcentric
 10+ years hacking embedded/RTOS,
storage, networks, and virtualization
 Last 3+ years directing engineering at
Gridcentric

3. This talk
Your innovation

4. Gridcentric VMS
 Delayed “fork()” for virtual machines:
 Take snapshot of running (fully configured) VM (bless)
 Spin up replica instances quickly and efficiently (launch)
 Re-use common memory pages between replicas

5. Extending Nova
 Nova is a framework, providing:
 A standardized API
 Messaging / RPC
 Database-backed ORM
 Nova can be extended by writing new:
 API extensions
 Custom “services”
 Nova CLI extensions
 Dashboard extensions

6. Nova API extensions
 Main module: nova.api.openstack.extensions
 Can:
 Add new resources
 Add new properties to existing resources
 Add new actions to existing resources
 Cannot:
 Replace / hook around existing actions

7. GC API extension
 Add new server actions:
 gc_bless – create state snapshot of running
instance
 gc_launch – launch new VM from state snapshot
 gc_discard – discard state snapshot
 Add new resource:
 gcservers – list VMS-capable compute hosts

8. Creating a new service
 Custom services can:
 Make RPCs to other Nova components
 Receive RPCs from Api server
 Access/modify the Nova data store

9. The nova-gc service
 Accepts RPCs from GC API extension
 For bless, launch, discard, etc
 Uses Nova ORM to CRUD server objects
 Interfaces to Gridcentric proprietary code to do
heavy lifting

10. Extending the nova client
 New actions can be surfaced to the nova CLI
client
 Need to be explicitly added via client extensions
 Extensions can be PIP-installable, etc
 GC client extension
 Adds bless, launch, discard, etc to nova CLI client

11. Extending the dashboard
 Horizon is a Django application
 New views/panes/etc can be added as
“Django installed applications”
 Horizon and extensions use the nova client
programmatically to access nova services.
 Ergo,you also need to write a client extension
and install it where Horizon is running

12. Extending the dashboard

13. Technical challenges
 Some parts of nova not 100% “extension ready”
 E.g. some built-in schedulers don’t route messages to
custom services
 IP tables rules need to be created through compute
service, but no interface exists for that
 Service framework makes assumptions w.r.t.
execution
 Different distributions do things differently
 E.g. paths, nova user, libvirt / qemu user

14. Business challenges
 Openstack is evolving extremely quickly
 Users/developers/vendors/operators are not always
synced up on the same release.
 The answer to a lot of issues is “wait for the next
release”.
 The Openstack market is still early
 Operators haven’t quite nailed down their
requirements/differentiation/solution set
 Lots of fragmentation = lots of confusion

15. Further reading
 Rackspace Extensions API intro:
http://docs.rackspace.com/openstack-extensions/apix-intro
 Rackspace Extensions (good examples!):
http://docs.rackspace.com/openstack-extensions/
 Gridcentric VMS extension: https://github.com/gridcentric/openstack
 Service architecture intro:
http://docs.openstack.org/developer/nova/service.architecture.html
 Extending Horizon (dashboard):
http://docs.openstack.org/developer/horizon/topics/tutorial.html
 Standard OpenStack API and extensions: http://api.openstack.org/

16. Thank you!
Email: tsmith@gridcentric.com
Link me in: https://www.linkedin.com/in/tsmithgc