Feature flags and controlled releases allow software features to be toggled on or off without deploying new code. The document discusses feature flags, their common uses, types including for release, operations, experiments and permissions. Real cases from Moip are presented, along with notes that feature flags are not a silver bullet and can introduce technical debt if overused. A demonstration of IFMAN, Moip's feature flag management tool, is advertised.

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FEATURE FLAGS AND
CONTROLLED RELEASES
Eduardo Colabardini
Chapter Leader @ Moip
eduardocolabardini@gmail.com
@ecolabardini
Lucas Queiroz
Software Engineer @ Moip
lucascqueiroz97@gmail.com
@lucascqueiroz97

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Agenda
• What are feature-flags?
• Common practices
• Types
• Longevity versus dynamism
• Release flags
• Real cases from Moip
• Not a silver bullet
• The superhero: IFMAN DEMO!

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What are feature-flags?
• Flags = Toggles = Bits = Flippers = Switches
• Variables used in conditional statements / strategy pattern
• A way to modify system behavior
• Enable/disable features

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Common practices
• Compiled / hardcoded
users = ['user1', 'user2']
• Command-line arguments
$ java MyApp user1,user2
• Property files
users = user1,user2
• Relational databases
> update user set role='admin' where id=1;
• Key-value stores
> sadd users user1

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Source: https://www.theverge.com/2016/1/4/10708590/facebook-google-android-app-crash-tests

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• Release
• Decouple deployment from releasing
• Canary releases - can be unstable, bleeding edge
• Alternative to feature branches
• Ops
• Operational aspects of a system
• Circuit-breaker
• Experiment
• A/B testing
• Permission
• Users permission, freemium model
Types

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Source: https://martinfowler.com/articles/feature-toggles.html

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Release flags
• Trunk-based development
• Continuous integration, delivery and
deployment
• Small commits / testing culture
• Reduce deployment risks
• Reduce costs of long lived branches
• Escape from merge hell

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Real cases from Moip
• Contestation central
• Third party transfers
• Two factor authentication
• Checkout
• OAuth 2.0
• Registered "boleto"

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Not a silver bullet
• Feature flag hell
• More test scenarios
• Keep track of feature-flags' states
• Harder to support, debug and replicate
problems
• Technical debt - "Toggle removal task" onto
the team's backlog
• Expiration dates (TTL) / fail a test
• Limit on the number of dynamic feature
flags in a system

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"Your first choice should be to break the feature
down so you can safely introduce parts of the
feature into the product. The advantages of doing this
are the same ones as any strategy based on small,
frequent releases."
- Martin Fowler

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The Superhero
https://github.com/moip

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RCurtain

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RCurtain

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JCurtain

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JCurtain

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The Superhero

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https://github.com/moip
Eduardo Colabardini
Chapter Leader @ Moip
eduardocolabardini@gmail.com
@ecolabardini
Lucas Queiroz
Software Engineer @ Moip
lucascqueiroz97@gmail.com
@lucascqueiroz97
Eduardo Colabardini
Chapter Leader @ Moip
eduardocolabardini@gmail.com
@ecolabardini
Lucas Queiroz
Software Engineer @ Moip
lucascqueiroz97@gmail.com
@lucascqueiroz97
Dúvidas?