Scala in practice

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Scala In Practice:
A Case Study
Tomer Gabel, newBrandAnalytics
April 2012

Some context

circa 2011:

• Startup with limited budget
• Cloud hosted, Linux based
• Com...

Strategy 101

Supplant
Evolve Refactor Complete
...

Data points

• Complete system rewrite impractical
– Too much code
– Business continuity a priority
– Cannot afford...

Why Scala?

• JVM-targeted, statically typed
• Success stories (Twitter, Foursquare,
LinkedIn)
• Active community
• Go...

Alternatives

• Dynamic
• LISP dialect

• Dynamic
• Java-like...

Scala in a nutshell

• Pervasive type inference

Scala in a nutshell

• Type aliases, closures, first class functions
and comprehensions Output:

Scala in a nutshell

• Imperative with functional-style
constructs

Scala in a nutshell

• Traits: static mixins

Scala in a nutshell

• Pattern matching FTW!

Scala in a nutshell

• Other goodies
– Option wrappers (no more NPEs!)
– Powerful collection framework
– Impl...

Caveat emptor

• Scala is bleeding edge
• You will get cut
– Learning curve
– Rough edges
– Partial/outdated docume...

Focal points

• Learning curve
• Tooling
• In production

Learning curve

• Risks:
– Functional constructs need getting used
to
– Few best practices:
• Coding convent...

Learning curve

• Mitigations:
– Relatively familiar syntax
– Seamless Java integration
• Evolve your codebase t...

Lessons learned

“New techniques are easy to explain.
Old techniques are hard to maintain.”
- an old Vulcan ...

Lessons learned

• Get a good grasp of the basics:
– Functions and closures
– Option wrappers
– Pattern match...

Lessons learned

• Avoid wacky syntax!
– Some common Scala libraries have
atrocious syntax (scalaz)
– Does this m...

Lessons learned

• Promote functional constructs:
– Intent over implementation
– Massive code savings
– Immutabilit...

Lessons learned

• Don’t go overboard
– Use implicits sparingly
– Avoid tuple overload
• x._1._2 * x._2 orElse x....

Focal points

• Learning curve
• Tooling
• In production

IDE Support

• Eclipse support via TypeSafe’s own
ScalaIDE
• IntelliJ IDEA support via plugin

IDE support

• Lower your expectations
• Don’t skimp on dev hardware!
• Use latest IDE/plugin builds
• Take your ...

IDE support

• Wonky debugging
– Java debuggers work…
– … with some caveats
• Step into synthetic stack frames
...

IDE support

• Except the unexpected
– Spurious error highlighting
• Especially with implicit conversions
• Dou...

Build tools

• Native Scala build tool is sbt
– Ivy2 (-> Maven repositories)
– Scala syntax
– Very powerful, sharp ...

Library ecosystem

• Surprisingly mature landscape!
• We use:
– ScalaTest + ScalaMock
– Squeryl
– Scalatra
• Use yo...

Focal points

• Learning curve
• Tooling
• In production

GC considerations

• Lots of generated classes
– Higher PermGen utilization
– Increase -XX:MaxPermSize

• Lots of in...

Other considerations

• Scalac emits lots of synthetic
code
– Deep call graph
– Intermediate stack frames
• Default...

Nasty surprises

• Different compiler, different edge-
cases
– Stack overflow may segfault
– Crash log may fail to ...

Codebase evolution

Import Java
codebase Refactoring

Tipping po...

Conclusion

• I would recommend Scala for:
– Startups willing to take the plunge
– Small teams of senior developers...

Questions?
… answers may be forthcoming

Afterword

• newBrandAnalytics for allowing the use of
the company name and R&D evidence
• TypeSafe and the amazing Sca...

Scala in practice

Scala in practice

Scala in practice

Scala in practice

Scala in practice

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