DEVOPS FOR EMBEDDED SOFTWARE DEVELOPMENTScott Hallock

May 20, 2013

Agenda• Introduction• What We Do• How We Do It• Strengths and Challenges

Introduction

BAIT • Build, Automation, Integration, and Test• Continuous integration and automated release for Linux

software products• 3-5 Linux-based operating systems• Software releases nearly every day• Build Linux from source thousands of times per day• Support a worldwide Linux developer community of more than

1,000• More than 50 actively developed codelines• Integrate more than 200 code changes per day

Objectives• High-level overview of embedded DevOps processes and

practices• Start an exchange of knowledge between embedded and

non-embedded DevOps communities• Interactivity

• Please interrupt to ask questions• Detailed, tangential discussions are welcome

Embedded Development Is Different• Tools don’t evolve quickly

• Command line compilers• Everybody loves the preprocessor• printf debugging• Eclipse viewed with suspicion

• Product focus• Customers get the code, not just the experience• Fix it, ship it, forget it• Standard release: zip archive• Many similar codelines under active development simultaneously

Continuous Integration

Review Build Deploy Test Integrate

Continuous Integration Deployment

• Datacenter-quality hardware• Rack-mountable form factor• Stable, controlled operating system and management

software• Well-defined power and thermal characteristics

Embedded Continuous Integration

Review Build Load Test Integrate

Target Load Challenges

• Developer-quality hardware• Irregular form factor• Unstable loading software, boot code, operating system• Unknown power and thermal characteristics• Slow and unstable JTAG, USB loading interfaces

Target Load Solutions• Single controlling server for each target hardware board• Physical access to production hardware

• Easily reconfigure physical racks to accommodate novel form factors

• Repair or replace unstable, malfunctioning target hardware

• Fault-tolerant software• Lots of retries!• Heuristics to infer target state based on observable outputs

• Change the target hardware design

Time Constraints

Review Build Load Test Integrate

90 minutes

15 minutes

Preverification

Build Load Test Integrate

90 minutes, many changes

Build

Review

60 minutes, one change

Automated Release

Build Test Approve git push

Code Change Control: git• http://git-scm.com• Distributed is great!

• Developers can work offline, at customer sites with no network access.

• Collaboration is easier. Everyone has complete history.

git Problems• Everyone gets everything

• Do you check in a helper binary every time you change it?• Did you accidentally commit some trade secrets and then revert

them later?• Did your developers include an estimate of your customers’

intelligence in their commit message?• You create integration tags fifty times per day.• Your continuous integration system creates “temporary” integration

branches twenty-five times per day.

git Problems• git trees become unusable over time. Are you garbage

collecting?• On your central repositories?• When you mirror your central repositories?• On your external release servers?• On your Continuous Integration build machines?

git Problems• Cherry-picking

• I can just have the two changes I want for today’s release? Great!• Breaks all traceability, barring commit message kludges

Codeline Definition: repo• http://source.android.com/source/using-repo.html• Allows for many git projects to be combined into a single

source tree and operated upon as a single entity.• Developers use it to download and sync code, most use

git commands for everything else.

<project name=“kernel/msm” path=“kernel” revision=“refs/heads/msm-3.4” /><project name=“kernel/lk” path=“bootable/bootloader/lk” revision=“refs/heads/master” />

repo: Project Addition

Build Test Approve git push!!!

repo: Branch Change

<project name=“kernel/msm” path=“kernel” revision=“refs/heads/msm-3.4” /><project name=“kernel/lk” path=“bootable/bootloader/lk” revision=“refs/heads/stable” />

<project name=“kernel/msm” path=“kernel” revision=“refs/heads/msm-3.4” /><project name=“kernel/lk” path=“bootable/bootloader/lk” revision=“refs/heads/master” />

repo: Branch Change

Build Test Approve git push!!!

repo: Branch Change• Merge?

• “master” branch contains dozens of bugs. You just merged them with your stable branch.

• Force push?• Now your customer doesn’t understand what happened to all the

changes they painstakingly integrated for the last month.

• Create new branch on release server?• Customer still has to re-integrate their changes.• At least the old branch is available for reference.

• Stop doing that!• How am I supposed to make my release?

repo: Shared Branches

customer-2.xml

<project name=“kernel/msm” path=“kernel” revision=“refs/heads/msm-3.4” /><project name=“kernel/lk” path=“bootable/bootloader/lk” revision=“refs/heads/customer-2” />

customer-1.xml:

<project name=“kernel/msm” path=“kernel” revision=“refs/heads/msm-3.4” /><project name=“kernel/lk” path=“bootable/bootloader/lk” revision=“refs/heads/customer-1” />

Gerrit: Code Review and More• https://code.google.com/p/gerrit/• Code review, access control, source code mirroring

Gerrit: Code Review• States Tracked:

• Code Review (-2 - +2): Peer opinion of design and code quality• Verified (-1 - +1): Code works at runtime

• Roles• Author/Committer• Approver• Integrator

Gerrit: Access Control• Most actions in Gerrit are access controlled

• Code visibility• Upload• Review• Merge

• Access control can be based on users, on local groups, or on LDAP groups.

• Access control is complex. Automation is recommended.

Gerrit: Mirroring

Master

Slave Slave Slave

• Single master• Slaves can’t mirror to other slaves• Smart git push based mirroring

• Better than any mirroring scheme not based on application layer knowledge of git

• Errors not handled gracefully• Obvious errors are re-queued for later retries

Code Aurora Forum• http://codeaurora.org

Other Tools• Electric Commander

• http://www.electriccloud.com/products/electriccommander.php

• Jira• https://www.atlassian.com/software/jira/overview

• BlackDuck• http://www.blackducksoftware.com/products/black-duck-suite

• Gitolite• http://gitolite.com/gitolite/

Strengths• Chasing the sun

• Operational teams in major timezones• Handoff procedure is well understood

• Cheap scaling• Use simple, dumb tools and relentlessly parallelize• Understand where human intervention is inevitable

• Sync, build efficiency• Custom software atop repo for very efficient repo syncs• Fastest clean builds in the business

• Automated release• Very complex branching structure is released automatically multiple

times per day

Challenge: Source Code Distribution

Master

Slave Slave!!! Slave

• Single master mirroring has scaling limits• Git push is CPU intensive

• Gerrit doesn’t report well when a slave is out of sync• Custom software needed

• An independent and easily monitored sync solution is desired

Challenge: Build Distribution

Build Test Approve git push

25GB x ~50/day

Boulder, San

Diego, Santa Clara, India, China,

Korea…

Challenge: Two-Way Integration

Internal Codeline

Integrated Codeline

Partner Codeline