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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
Slides: http://slidesha.re/XfgUZ7