This document discusses several approaches for upgrading OpenStack deployments from one version to another, including: upgrading all nodes at once in a short time window; migrating nodes in staged groups; and upgrading nodes individually using system-wide orchestration that supports components of multiple versions simultaneously. It emphasizes that orchestration is key, and that the physical layout, networking transitions, collaboration with developers, and high availability requirements all complicate the upgrade process. The document advocates for sharing best practices, coding for upgradeability, and collaborating with tools like Crowbar that integrate orchestration and Chef to automate upgrades while maintaining features like discovery, networking configuration and operating system installation.

1. Greg Althaus
Dell, Principal Engineer
http://lifeatthebar.co
m

2. • The “Problem“ with Migration
• Paths to Nirvana (or Roads to Perdition)
• Alternatives
• An Opinion
• Discussion
F G
H
http://learn.genetics.utah.edu/content/begin/cells/organelles/

3. • OpenStack has 3 month release major/minor cycle
• Major version every 6 months
• Minor version (but important) 3 & 6 months after release
• Lots of Changes
• Bugs are fixed
• Operating Systems upgrade
• New technologies appear
• Whole projects are split off
• We expect operators to
• Keep systems running
• Never loose data
• And… Stay up to date http://cdn2.arkive.org
sockeye-salmon-predated-by-grizzly-bear-on-migration-upstream.jpg

4. • What are we upgrading?
• OpenStack - Yes!
• Dependent packages - Probably?
• Base OS - Maybe?
• What is the state during the "in-between" time?
• Infrastructure downtime?
• VM downtime? VM Reboot? Controlled/Informed?
• Availability Windows?
• What contingency plans?
• Dry run? Maybe.
• Recover by going backwards? Maybe.
• What level of safety and trust do you need?
• Assure data integrity?
• Assure Infrastructure Integrity?
• Maintain Security?
• How long can the migration take?
• Big bang move or gradual migrate?
• How will my API consumers/ecosystem cope?
• Can Keystone Grizzly work with Folsom Nova???
• What about futures? G.1 to G.2? H to I?
• Can I skip versions? Jump from G to I?
http://www.publicdomainpictures.net
Steep Steps by Peter Griffin

5. • Beginning Answers
• Distros will manage dependencies and packaging
• We can’t lose data or compromise security
• Infrastructure state and integrity will vary by solution
• Assumption of Staging
• Some managed environment (not a manual deploy)
• Staging/test environment to get "familiar" with the problem.
• Maintenance window for production - limits scope of change
• Step-wise changes are OK (big bang is not required)
• We can make trade-offs to defray expensive requirements
• Beyond Assumptions… Paradigm Shifts
• There are shared best practices
• Upgrades can be automated in a sharable way
http://www.theemailadmin.com/wp-content/uploads/2012/09/GFI229-hot-water-migration.jpg

6. All the nodes update to the latest code
in a short time window
• Details:
1. Cookbooks include update (instead of install) directives.
2. Control upstream package point (e.g. apt-update when appropriate)
3. Force chef-client run
4. Now at new level
• Considerations
• Pros: Potentially fast, continuous operation
• Cons: Don't mess up, it is your production environment
• Scope: Security updates
• Code Assumptions:
• System can function through service restarts.
• Underlying data models don't change or migrate appropriately.

7. Nodes migrate in staged groups
• Details:
1. Choose subset of machines and quiesce them.
2. Update set
3. Freeze state (by tenant)
4. Migrate service/tenant content
5. Repurpose after complete.
• Considerations
• Pros: Safer, more controlled, and can move tenants as needed
• Cons: Takes longer, still has cut-over point, but less open
http://allgodscrittersgotrhythm.blogspot.com/2010_08_01_archive.html

8. Nodes changed individually by a system-wide
orchestration that supports components of multiple
versions
• Details
1. Components must be able to straddle versions
2. Orchestration updates core components to new version
3. System as a whole queiseces and is validated (requires self
test)
4. Orchestration individually migrates components (return to step
3)
• Considerations
• Pros: Creates a highly resilient system that handles higher rate of
http://www.grizzlycentral.com/forum/grizzly-tire-wheel-combos/1204-upgrade-tires-grizzly.html

9. • Orchestration (not just deployment automation)
• Awareness of physical layout is required
• Must respect fault zones to sustain HA
• Proximity of resources matters for migration
• Networking transitions are essential
• Collaboration with development teams is essential
• Components must support current and previous
• Upgrade plan must be baked into configuration and tested
• Upgrade dependencies must be 1) clear and 2) minimized
• HA complicates upgrades
• Upgrade can be detected as a failure
• HA system must be able to bridge versions

10. • Deployment Upstream Cookbooks/Modules
• Best Practice Discussions
• Code for Upgradeability
• Crowbar Collaboration
• Upgrade is a FEATURE!
• Orchestration + Chef
• Pull from Source Deployments
• System Discovery
• Networking Configuration
• Operating System Install
http://farm3.static.flickr.com/2561/3891653055_262410bc31.jpg