OpenStack Nova - Developer Introduction
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This document provides an overview of Nova, OpenStack's compute service. It discusses Nova's architecture, code structure, API concepts, upgrade process, and how different groups work together as part of the upstream community. The new upgrade process aims to minimize downtime by expanding the database schema, restarting services individually, and signaling services to reload configuration. Collaboration across various groups with different perspectives is important to OpenStack's open development model.
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OpenStack Nova - Developer Introduction
- 1. Nova Deep Dive John Garbutt, Principal Engineer, Rackspace @johnthetubaguy March 2016
- 2. Image FPO 2 Why is johnthetubaguy talking? 2
- 3. Image FPO 3 Do you really play the Tuba? 3
- 5. 5 to provide massively scalable , on demand, self ser vice access to compute resources OpenStack Nova’s Mission http://docs.openstack.org/developer/nova/project_scope.html
- 8. 8 Cells v1 v2 • Cells is optional • Not all features supported • Sync instance between DBs • Default is one v2 cell • New API database • Tools to migrate from cells v1 API Compute Cell 1 Compute Cell 2 Compute Cell 3
- 9. 9 API
- 10. 10 API Users The Absent The Active Multi-Cloud Ops & Dev • Cloud upgrades • But old script works • Uses newest APIs • Check availability • Multiple clouds • Different versions • Single script • Who is using what? • How to evolve API? https://dague.net/2015/06/05/the-nova-api-in-kilo-and-beyond-2/
- 11. 11 API Evolution v2.0 v2.1 • First API • Base + Extensions • Now Deprecated • No Extensions • Evolve using “Micro-versions” • Better Validation http://developer.openstack.org/api-ref-compute-v2.1.html http://developer.openstack.org/api-guide/compute/server_concepts.html#moving-servers
- 12. 12 API Concepts • Servers, Flavors, Key Pair, Server Groups • Image, Volume, Network Port • Hosts, Aggregates • More Info: – http://developer.openstack.org/api-ref-compute-v2.1.html – http://developer.openstack.org/api-guide/compute/server_concepts.html#moving-servers
- 14. 14 Code Structure – API Request to Hypervisor • API: v2.1 and legacy – https://github.com/openstack/nova/blob/master/nova/api/openstack/compute/servers.py#L99 5 • “api.py” façade classes – https://github.com/openstack/nova/blob/master/nova/compute/api.py#L2416 • RPC Managers and client: Compute, Conductor, Scheduler, etc – https://github.com/openstack/nova/blob/master/nova/conductor/rpcapi.py#L353 – https://github.com/openstack/nova/blob/master/nova/conductor/manager.py#L524 – https://github.com/openstack/nova/blob/master/nova/compute/manager.py#L2957 • Compute Driver – https://github.com/openstack/nova/blob/master/nova/virt/ironic/driver.py#L1068
- 15. 15 Code Structure – Save to Database • Compute Manager – https://github.com/openstack/nova/blob/master/nova/compute/manager.py#L2832 • Instance Object – https://github.com/openstack/nova/blob/master/nova/objects/instance.py#L120 – https://github.com/openstack/nova/blob/master/nova/objects/instance.py#L699 • DB façade and impl – https://github.com/openstack/nova/blob/master/nova/db/api.py#L793 – https://github.com/openstack/nova/blob/master/nova/db/sqlalchemy/api.py#L2781 – https://github.com/openstack/nova/blob/master/nova/db/sqlalchemy/models.py#L196 – https://github.com/openstack/nova/blob/master/nova/db/sqlalchemy/migrate_repo/versions/266_add_instance_tags.py#L16 – API DB: https://github.com/openstack/nova/blob/master/nova/objects/request_spec.py#L396
- 18. 18 Everyone Involved Contributed Code Regularly Reviews Code <project>-core & CPL & Czar <project>-driver & PTL Groups with Shared Context
- 19. 19 Different Views of Project Upstream Mission Upstream Reality Personal view of Upstream My Solution My Solution
- 21. Image FPO 21 What can we all learn from To Kill a Mockingbird? 21
- 22. 22 You neve r re ally unde r stand a pe r son until you consider things from his point of view … until you climb into his skin and walk around in it. To Kill a Mocking Bird By Harper Lee
- 23. Image FPO 23 Problem First, Solution Second 23
- 25. 25 Upgrade
- 26. 26 Upgrade Needs • Scope: – To the next release – Continuous Deployment • Control plane vs Data plane • Existing Configuration works • Warn before removing features http://governance.openstack.org/reference/tags/#project-assertions-tags
- 27. 27 Old Process Turn Off Old DB Upgrade Turn On New
- 29. 29 New Upgrade Process Expand DB Schema Restart API and Control Plane Restart n-compute SIGHUP all services
- 31. 31 Nova Architecture API Nodes Behind LB Compute Compute Compute Compute Compute Database Message Queue Conductor(s) Other Control Nodes Isolate from DB using oslo.versionedobjects Versioned RPC Signature Schema and Data Migrations Graceful Shutdown RPC Signature
- 32. 32 New Upgrade Process API Nodes Behind LB Compute Compute Compute Compute Compute Database Message Queue Conductor(s) Other Control Nodes 1 2a 3 4 2b
- 33. 5 M I L L I N G T O N R O A D | H AY E S , U N I T E D K I N G D O M U B 3 4 A Z U S S A L E S : + 4 4 ( 0 ) 2 0 8 71 2 6 5 07 | U K S U P P O R T: 0 8 0 0 9 8 8 0 3 0 0 | W W W. R AC K S PAC E . C O M © RACKSPACE LTD. | RACKSPACE® AND FANATICAL SUPPORT® ARE SERVICE MARKS OF RACKSPACE US, INC. REGISTERED IN THE UNITED S TATES AND OTHER COUNTRIES. | WWW.RACKSPACE.COM Thank you @johnthetubaguy
Editor's Notes
- Rackspace public cloud powered by OpenStack Nova Started working on OpenStack at Citrix in 2010 Joined nova-core in June 2013, Nova PTL for Liberty and Mitaka Image from unsplash.com
- What is Nova?
- http://docs.openstack.org/developer/nova/architecture.html
- Lets take a look at our users, and what they want. Reference: https://dague.net/2015/06/05/the-nova-api-in-kilo-and-beyond-2/
- https://upload.wikimedia.org/wikipedia/commons/9/98/Elephas_maximus_%28Bandipur%29.jpg Three blind people meet an elephant.
- Infrequent contributor says: Why does everyone hate my idea? OpenStack users groups of people who all trust each other to scale out what they do. We need to take care these groups do not exclude. To do that, lets take a look at how these groups form.
- View of perfection Current state is quite different, Note: bits they don’t want, and missing bit Internal view of rest of the world and what they want is not complete After discussion upstream you see a different picture
- http://docs.openstack.org/project-team-guide/introduction.html#the-four-opens Open Source not open core Open design summits Open development – reviews, roadmaps Open community – vibrant dev and user community We aim to be very Open, how do we keep that.
- https://upload.wikimedia.org/wikipedia/commons/1/16/Mimus_polyglottos1.jpg
- Empathy is important.
- Build empathy by discussing the problem. https://upload.wikimedia.org/wikipedia/commons/e/e5/Rubiks_cube_scrambled.jpg
- https://commons.wikimedia.org/wiki/File:Sonyhdrfx1.jpg https://commons.wikimedia.org/wiki/File:Powerpoint_icon.jpg https://commons.wikimedia.org/wiki/File:The_Friends_Stage_cropped.jpg https://upload.wikimedia.org/wikipedia/commons/e/e5/Rubiks_cube_scrambled.jpg 1) Summit talks are recorded, the Design Summit is not. Look out for ttx¹s Design Summit 101, like this one: https://libertydesignsummit.sched.org/event/e480edc1483038153cf2dcd9968668 6 a The technical debate and planning happens in the Design Summit sessions, not the conference. PowerPoint is banned in the Design Summit, its about debate not updates. Mon: ops, Tues: cross project, Wed-Thurs: fishbowls/work sessions, Friday: meetup 2) Agree the problem, then discuss solutions Don¹t ask ³how to get my code merged². Instead ask ³how can I solve this problem I have² For more details see: https://www.openstack.org/summit/tokyo-2015/videos/presentation/working-wi t h-upstream-openstack-deadlines-and-internal-deadlines 3) Find a friend, so its easier to speak up Speaking up at a Design Summit is crazy scary. This is normal. Don¹t panic! Sit with a friend. If you both have the same question, it feels easier to ask it. Find someone you know on the front row of the debate, and ask them to loop you in. Look out for suggested pre-reading, makes it easy to understand the context. Anyone can write on the etherpad, ideally add your name. 4) First time running a design summit session? See Step 2. Also ask some folks who do it regularly for advice. 5) Enjoy matching IRC handles to faces. Its fun.
- https://upload.wikimedia.org/wikipedia/commons/7/78/Airforce_forklift.jpg https://images.unsplash.com/photo-1429497419816-9ca5cfb4571a?q=80&fm=jpg&s=4bf1164d23eea4f04aeefe1732149cf3 This talk will focus on the control plane
- Data plane / VM downtime Control plane / API downtime = Lost income and Support Calls
- http://www.danplanet.com/blog/2015/06/26/upgrading-nova-to-kilo-with-minimal-downtime/ Aim: zero downtime. Note: no rollback
- http://docs.openstack.org/developer/nova/architecture.html
- Flow: API (-> DB) -> Conductor (-> Scheduler) -> Compute (talks to other services) Why: Scale small and large: API requests vs Compute nodes Note Upgrade features.
- (1) Expand DB, checks all data migrations are complete, removes any cruft from previous releases (2) Pin RPC, upgrade all the control plane together, but conductor first (3) Talk about graceful compute shutdown, and its limitations (4) Un pin RPC by rechecking
- To find out more…