Confidential and proprietary materials for authorized Verizon personnel and outside agencies only. Use, disclosure or distribution of this material is not permitted to any unauthorized persons or third parties except by written agreement.

Functional Programming at Verizon OnCue6th September 2014

Timothy Perrett

Service Architect

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Secret project.Formally Intel Media; purchased by Verizon in early 2014.

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Completely “green field”.Every conceivable system component was being created from scratch.

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Scala Services.Using FP for all platform services from day one.

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Challenges.We’ve broken our fair share of eggs making this particular omelet.

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Explosion in team size.Engineering group expanded by an order of magnitude within the first year.

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Utilize market conditions.Market supply of specific skills is nearly always eclipsed by supply of candidates with strong engineering aptitude.

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Every engineer is unique.Engineers are people; not pluggable resources.

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Effort of learning FP

Time in a single language

Ease of learning FP

Time

Eff

ort

Confidential and proprietary materials for authorized Verizon personnel and outside agencies only. Use, disclosure or distribution of this material is not permitted to any unauthorized persons or third parties except by written agreement. 10

Effort of learning FP

Time in a single language

Ease of learning FP

Time

Eff

ort

Less unlearning;FP more intuitive

Confidential and proprietary materials for authorized Verizon personnel and outside agencies only. Use, disclosure or distribution of this material is not permitted to any unauthorized persons or third parties except by written agreement. 11

Effort of learning FP

Time in a single language

Ease of learning FP

Time

Eff

ort

Large unlearningperiod; FP “is hard”

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Perceived difficulty. “Constant struggle against your own instincts”

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Effort of learning FP

Cost of learning FP vs time in multiple PL paradigms

Time in n-PL Ease of learning FP

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Strong teams need both.Embrace change, tackle challenges together.

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Distribute team education.Centralized education alone is not enough. Use education, pair programming and team sessions.

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Provide space to learn.Be prepared to allow the team to make mistakes, give room to learn and encourage experimentation.

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Libraries can be dangerous.Encouraging reuse across a large team results in inconsistent, lossy abstractions.

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Functional core. Imperative API.Internally functional libraries can have optional imperative APIs for easier migration / learning curve.

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val config: Task[Config] = knobs.loadImmutable(Required(FileResource(...))) or knobs.loadImmutable(Required(ClassPathResource(...)))

val connection: Task[Connection] = for { cfg <- config usr <- cfg.require[String]("db.username") pwd <- cfg.require[String]("db.password") prt <- cfg.lookup[String]("db.port") } yield Connection(usr,pwd,port)

Code Example

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import instruments.timer

val taken = timer( name = "time-taken", description = "Time taken to compute Foos")

def thing(x: Bar): Foo = taken.time { // compute Foo }

def thingAsync(x: Bar): Task[Foo] = taken.timeTask(taskComputingFoo)

Code Example

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Writing from scratch is a winIf you can: build it. Taylor to your orgs’ needs.

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Numerous internal libraries.Monitoring. Configuration. Graph Processing. Logging. Functional RPC system… and many more.

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Minimal external dependencies*Scalaz. Scalaz-Stream. Scodec. Shapeless.

*working on the jvm often makes this problematic (log4j, slf4j etc).

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Was it worth it?100% yes. Choosing to use functional programming has ultimately eased our lives considerably.

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Change is easy.So easy we don’t even notice the daily win.

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New and exciting wins the day.Happy teams are productive teams.

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We’re hiring!At every level of the stack. Yes, really.

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Q&AThank you for listening.