Continuous Deployment is a strategy for releasing software.

More Irregular <------------                   -------------> More regular
Once per iteration    Every Month   Two weeks   1 week   Few days   Nightly

[<========= Waterfall =========>]
                      [<=========== Agile ==========>]
                                             [ BAU/firefighting/noprocess ]

More Irregular <------------                   -------------> More regular
Once per iteration    Every Month   Two weeks   1 week   Few days   Nightly

[<========= Waterfall =========>]
                      [<=========== Agile ==========>]
                                             [ BAU/firefighting/noprocess ]

TOO SLOW

• Even nightly is not responsive enough in many cases
  • Vulns
  • Urgent/Important fixes
• If too slow, every release is a nightmare
• Delays cause inefficiencies
  • Merge hell
  • Wasted code/time

Releases are a point of friction
The larger the friction, the more the project struggles.

Commit, Test, Deploy

Continuous Deployment
Commit Deploy

• Small commits
• All commits!
• No feature branches
  • Hide "in progress" work with feature flags

• "Feature branching in code"
• Can be as complex as you want
  • "Dark launch"
  • Enable for admins only; (random?) list of users; user cohort
  • Enable after certain date
• Built-in kill switches

• Continuous Integration (poorman: manual)
• Should complete quickly
• When they fail, the impending deployment is abandoned

• Triggered by a successful run of the tests (poorman: manual)
• As few commands as possible! Should be frictionless
• Should be no cause for fear

• Should always be possible to roll back to the previous commit
  • The smaller the changes, the easier this is
• Write a test to cover the break
• Strategy assumption: "Every Defect Once"

• CD is actually a risk reduction strategy
• Presupposes what you're doing now is working ;)
• Going slower reduces frequency of risk, but massively increases magnitude

• More responsive
• Solid incentive to develop good testing habits
• Less pressure
• Less waste
• Improved developer attitude

CD lets you go fast with confidence

• "I work for a financial institution, and..."
  • Your problem is the test suite, not CD
• "You're outsourcing QA to your customers!"
  • You can still involve QA - deploy to a staging environment simultaneously, and/or give them access to new features on production with feature flags
  • You already outsource QA to your customers to an extent ;)
• "Batching up changes is safer"
  • Waiting longer does not correlate with higher quality
  • Other eyes checking does - which you can do without batching changes

• "We'd never get signoff for this"
  • "We're losing millions" almost never goes through signoff either
• "Legislation forbids us from..."
  • Devs change stuff all the time, in violation of legislation! See previous point
  • Some dev always has root access
• "GST goes up to 15% on XXX..."
  • Manage dependency issues with feature flags
• "Our tests now take hours to run!"
  • Test cluster
• "That's all good for you SaaS guys, but..."
  • Google Chrome
  • Moodle

• CD has significant mindshare in the tech startup community
• Major players are already adopting it
• You will be left behind - nobody who has switched switches back
• Try it on a small/new project to test the concept in your mind

• <nigel@shoptime.co.nz>, nigel.mcnie.name, @nigelmcnie

Credits

• Thx Andy for the slides
• Thx Grant for the prod