An experience report detailing how our team at Verizon used functional programming to build our awesome service platform.

1. Functional Programming
at Verizon OnCue
6th September 2014
Timothy Perrett
Service Architect
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.

2. Secret project.
Formally Intel Media; purchased by Verizon
in early 2014.
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3. Completely “green field”.
Every conceivable system component was being
created from scratch.
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4. Scala Services.
Using FP for all platform services from day one.
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5. Challenges.
We’ve broken our fair share of eggs making this
particular omelet.
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6. Explosion in team size.
Engineering group expanded by an order of
magnitude within the first year.
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7. Utilize market conditions.
Market supply of specific skills is nearly always
eclipsed by supply of candidates with strong
engineering aptitude.
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8. Every engineer is unique.
Engineers are people; not pluggable resources.
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9. Effort of learning FP
Effort
Time
Time in a single language
Ease of learning FP
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10. Effort of learning FP
Effort
Time in a single language
Ease of learning FP Less unlearning;
FP more intuitive
Time
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11. Effort of learning FP
Effort
Time
Time in a single language
Large unlearning Ease of learning FP
period; FP “is hard”
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12. Perceived difficulty.
“Constant struggle against your own instincts”
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13. 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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14. Strong teams need both.
Embrace change, tackle challenges together.
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15. Distribute team education.
Centralized education alone is not enough. Use
education, pair programming and team sessions.
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16. Provide space to learn.
Be prepared to allow the team to make mistakes, give
room to learn and encourage experimentation.
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17. 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. 17

18. Libraries can be dangerous.
Encouraging reuse across a large team results in
inconsistent, lossy abstractions.
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19. Functional core. Imperative API.
Internally functional libraries can have optional
imperative APIs for easier migration / learning curve.
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20. Code Example
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)
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. 20

21. Code Example
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)
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22. Writing from scratch is a win
If you can: build it. Taylor to your orgs’ needs.
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23. Numerous internal libraries.
Monitoring. Configuration. Graph Processing.
Logging. Functional RPC system… and many more.
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24. Minimal external dependencies*
Scalaz. Scalaz-Stream. Scodec. Shapeless.
*working on the jvm often makes this problematic (log4j, slf4j etc).
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25. Was it worth it?
100% yes. Choosing to use functional programming
has ultimately eased our lives considerably.
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. 25

26. Change is easy.
So easy we don’t even notice the daily win.
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27. New and exciting wins the day.
Happy teams are productive teams.
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28. We’re hiring!
At every level of the stack. Yes, really.
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29. Q&A
Thank you for listening.
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