Feature FlagRoll Out & Roll Back without Deployment

Feature Flag?New Feature On/Off

Index

1. Problems before Feature Flag

2. Benefits

3. Weak Points

4. Libraries

Problems before Feature Flag

Deployment == Roll Out

Deployment

before Feature Flag

Problem 0.No Test in Production

Test ENV != Prod ENV

Problem 1.Unclear Delivery

Time

From Click To Roll Out: Maybe.. 30 minutes

Problem 2.No Way to Dog

Fooding

QA => All Users

RollBack

before Feature Flag

Problem 3.Slow Delivery

From Click To Roll Out: Maybe.. 30 minutes

Solution.New Feature On/Off

to Some Users

One Click UI

Code Level

if FeatureFlag.active?('fetureFoo', user) c = a/belse c = b == 0 ? 0 : a/bend

Feature Flag Service

• Create if new flag is detected.• List flags.• Update a flag.• Delete too old flags.

Infrastructure

After Feature Flag

Deployment

after Feature Flag

Benefit 0.Test in Production

Benefit 1.Clear & Fast Delivery

Time

One Click & Real Time Roll Out

Benefit 2.Easy Dog Fooding

QA => Internal User => All

Rollback

After Feature Flag

Benefit 3.Fast Roll Back

One Click & Real Time Roll Back

Unexpected Benefit 4.

Simple A/B Test

Weak Points

• Uncooperative Members• Too Big Changes to Use Feature Flag• Obsoleted Feature Flags are Debts• Dependency on Each Feature Flags

No feature flag can be better

• Brand New API• Clear & Tiny Changes• Fixing a bug that makes something

worthless

Weak Point 0.Uncooperative

Members

Solution 0.Code Review!

No Flag No Merge

Weak Point 1.Too Big Changes

to use Feature Flag

Solution 1.Apply to End Point

Solution 1-0. in Method

if FeatureFlag.active?('fetureFoo', user) c = foo(1, 2)else c = deprecated_foo(1, 2)end

def foo(a,b) ... ...end

def deprecated_foo(a,b) ... ...end

Solution 1-0. in Classif FeatureFlag.active?('fetureFoo', user) c = Foo.new(1, 2)else c = DeprecatedFoo.new(1, 2)end

class Foo(a,b) ... ...end

class DeprecatedFoo(a,b) ... ...end

Solution 1-0. in HTML# Javascript<option ng-show=“FeatureFlag.is_active(‘fetureFoo', user)" value="foo1"/><option ng-hide=“FeatureFlag.is_active('fetureFoo', user)" value="foo2"/>

# Server Rendering<% if FeatureFlag.active?('fetureFoo', user) %> <option value="foo1"/><% else %> <option value="foo2"/><% end %>

Weak Point 2.Obsoleted Feature Flags are

Debts

Solution 2.Clean Up in The

Sprint

Weak Point 3.Dependency on Each

Feature FlagFeature Flag in Feature Flag in Feature Flag in …

Libraries

• rollout for Ruby• Gutter for Python• Togglez for java

Reference• https://martinfowler.com/articles/feature-

toggles.html• https://martinfowler.com/bliki/

FeatureToggle.html• https://msdn.microsoft.com/en-us/

magazine/dn683796• http://apptimize.com/feature-flags-launch/

Q & A