Flag Your Features with Rollout and Degrade

In light of James Golick's recent untimely passing, here's a brief overview of rollout (https://github.com/FetLife/rollout) and degrade (https://github.com/jamesgolick/degrade), 2 gems which provide a simple interface for dynamic activation and deactivation of your app's features. We'll discuss why we might want to use feature flags and how to implement them using James' gems.

Links:
https://github.com/jamesgolick/degrade/blob/master/lib/degrade.rb#L12-L20
https://news.ycombinator.com/item?id=8804624
https://medium.com/@benkaufman/remembering-james-golick-23c1dc3ab920
https://medium.com/@jill380/the-adventurous-life-of-james-golick-bda4a33137b6

Transcript

1. FLAG YOUR FEATURES WITH ROLLOUT AND DEGRADE Ariel Caplan
2. WHAT ARE FEATURE FLAGS? • Turn bits of code on and off • On/Off • This/That
3. • Experimental Code • Syncing apps in an SOA ecosystem WHY FEATURE FLAGS? Client Service v1 v2
4. WHY FEATURE FLAGS? • Experimental Code • Syncing apps in an SOA ecosystem • Consuming internal services (where you don’t have control) Client Service v1 v2
5. • Experimental Code • Syncing apps in an SOA ecosystem • Consuming internal services (where you don’t have control) • Consuming external services (which experience downtime) WHY FEATURE FLAGS? Client Service
6. • Experimental Code • Syncing apps in an SOA ecosystem • Consuming internal services (where you don’t have control) • Consuming external services (which experience downtime) • Debugging tools WHY FEATURE FLAGS?
7. ROLLOUT REQUIRES REDIS rollout = Rollout.new(redis) ! ! Technically it doesn’t require redis… but use it anyway.
8. ACTIVATION/DEACTIVATION # activate for all users rollout.activate(:chat) ! # deactivate for all users rollout.deactivate(:chat)
9. A/B TESTING # activate for a percentage of users rollout.activate_percentage(:chat, 20) ! # check if the user gets the new feature! rollout.active?(:chat, User.first)
10. WHERE TO INSERT BRANCH POINTS?
11. BRANCH POINT: CONTROLLER class ExperimentalController < ApplicationController ! def index if rollout.active?(:my_feature) @entities = MyFeature.get_entities(params) respond_with @entities else head(:service_unavailable) end end ! end
12. BRANCH POINT: MODELS class ResponseFormatter ! attr_reader :array ! def initialize(array) @array = array end ! def output if rollout.active?(:safe_json_format) { 'array' => array } else array end end ! end
13. #PROTIP: USE HUBOT class FeaturesController < ApplicationController ! def update rollout.activate(params[:id].to_sym) head :ok end ! def destroy rollout.deactivate(params[:id].to_sym) head :ok end ! end
14. PART II: DEGRADE “Because Stuff Doesn’t Work!”™
15. [OPTIONAL] SETTINGS APLENTY! degrade_my_feature = Degrade.new( redis, name: :my_feature, sample: 5000, minimum: 100, threshold: 0.1, errors: [StandardError], failure_strategy: -> { rollout.deactivate(:my_feature) } )
16. WRAP YOUR UNRELIABLE SERVICES if rollout.active?(:my_feature) data = degrade_my_feature.perform do Net::HTTP.get('mega-downtime.com', '/data.json') end end
17. DEGRADE DOESN’T AFFECT YOUR CODE def perform begin mark_request yield rescue *@errors => e mark_failure raise e end end https://github.com/jamesgolick/degrade/blob/master/lib/degrade.rb#L12-L20
18. PIMP MY FAILURE STRATEGY degrade_my_feature = Degrade.new( redis, name: :my_feature, failure_strategy: -> { rollout.deactivate(:my_feature) OutageNotifier.notify(downtime: :my_feature) MyFeatureActivatorWorker.perform_in(30.minutes) } )
19. JAMES GOLICK http://jamesgolick.com/ https://news.ycombinator.com/ item?id=8804624 https://medium.com/ @benkaufman/remembering- james-golick-23c1dc3ab920 https://medium.com/@jill380/the- adventurous-life-of-james-golick- bda4a33137b6
20. Ariel Caplan @amcaplan amcaplan.ninja
 

21. Ariel Caplan @amcaplan amcaplan.ninja
 
 Thank you to: YOU!