ITERATORSI T E R A T O R S @luksow
Microservices in Scala
theory & practice
Łukasz Sowa, Warsaw Scala Enthusiasts 2015-07-08

ITERATORSI T E R A T O R S @luksow
Hi, I'm Łukasz
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Co-founder, engineer @ Iterators (https://iterato.rs)
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ScalaWAW organizer (http://meetup.com/ScalaWAW)
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Specializes in: highly concurrent & distributed systems
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Pizza, beer & football lover
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http://luksow.com (soon!)
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contact@luksow.com
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@luksow

ITERATORSI T E R A T O R S @luksow
What's in it for you?
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Learn
– What are microservices?
– How to implement them using Scala
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Takeaways
– Feel enthusiastic but cautious about microservices
– Be able to design your next project using microservices and Scala
– Experience with (almost) production-ready system designed with MSA
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Nope
– Yet another REST microframework showcase
– 'Microservices will solve all your problems'-type bullshit marketing

ITERATORSI T E R A T O R S @luksow
Theory
In a nutshell

ITERATORSI T E R A T O R S @luksow
What are microservices?
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Architectural style (MSA)
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System is composed of multiple services
– Small*
– Independently deployed
– Communicate using (lightweight) protocols
– Organized around business capabilities
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Bounded Context (DDD) or Single Responsibility
Principle (OO) implemented in architecture

ITERATORSI T E R A T O R S @luksow
Practice
For the next ~45 minutes

ITERATORSI T E R A T O R S @luksow
Let's design!
Design a system that allows users to login/register using FB, email-password or
codecard. Authenticated user can subscribe to different events from BTC
markets (ex. rate changed, volume over N, ask below M etc.) and get real-time alerts
about them. Make sure to gather relevant business metrics.
auth-fb auth-pass auth-codes
btc-users
btc-ws
identity
metrics
session
token
frontend
btc-market
load balancer

ITERATORSI T E R A T O R S @luksow
Demo
In the meanwhile, please download the Internet...
$ git clone https://github.com/theiterators/reactive-microservices.git
$ cd reactive-microservices
$ sbt compile
$ # import into your favourite IDE

ITERATORSI T E R A T O R S @luksow
Private data stores
auth-fb auth-pass auth-codes
btc-users
btc-ws
identity
metrics
session
token
btc-market
MongoDB
Redis PostgreSQL PostgreSQL
PostgreSQL
MongoDB
Event journal

ITERATORSI T E R A T O R S @luksow
Shared data stores
auth-fb auth-pass auth-codes
btc-users
btc-ws
metrics
session
btc-market
MongoDB
token
Redis PostgreSQL PostgreSQL
PostgreSQL
identity
MongoDB
Event journal

ITERATORSI T E R A T O R S @luksow
Metrics flow

ITERATORSI T E R A T O R S @luksow
BTC WS state machine

ITERATORSI T E R A T O R S @luksow
Summary
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Scala's toolbelt (Akka, Play) is ready for MSA
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Lots of problems and dilemmas on MSA way
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Monoliths are easy :-)
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There are more fine tools for Scala, ex. Finagle
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Production code is only half story, the other is
operations, which are extremely hard in MSA

ITERATORSI T E R A T O R S @luksow
Hacking time!
Yay!

ITERATORSI T E R A T O R S @luksow
How to spend next 60 minutes?
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Ideas
1. SPA frontend (Scala.js?)
2. SBT – add Play projects to runAll, clean garbage
3. Metrics – add to other projects
4. Rewrite Play websockets to Akka HTTP websockets
5. Add more BTC markets, update actor protocol
6. Bump dependencies version (migrate to Slick 3, Play 2.4)
7. Simplify streams logic (error handling)
8. Modify business logic (ex. add different authorization levels)
9. Change gateways to use reconnection and/or long-running connections
10. Add new authentication method (ex. G+, SMS)
11. Propose a deployment method (ex. integrate with sbt-assembly or sbt-native-packager)
12. Build deployment environment
13. Integrate with service discovery & configuration management service (ex. ZooKeeper)
14. Think about contract management (ex. integrate with Swagger)
15. Integrate with centralized logging solution (ex. integrate with Logstash) and implement tracing (ex. Correlation-id)
16. Invent a way of testing – single services, subsets or whole solution
17. Your cool idea goes here!
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Subscribe now to http://meetup.com/ScalaWAW to be notified about microservices hackathon in July or August
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Ask me anything! (about ideas, this activator, ScalaWAW, running a software company, ...)

ITERATORSI T E R A T O R S @luksow
Thanks!
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Łukasz Sowa
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http://luksow.com
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https://iterato.rs (yes, hiring!)
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contact@luksow.com
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@luksow