Codemotion 2015,
Berlin, Germany
Building a
Reactive RESTful API
with Akka Http & Slick
Dan Persa - @danpersa

Dan Persa
● Senior Software Engineer
● Twitter: @danpersa
● dan.persa@zalando.de

EUROPE’S LEADING ONLINE FASHION PLATFORM
15 countries
3 fulfillment centers
16+ million active customers
2.2+ billion € revenue 2014
130+ million visits per month
9.000+ employees
Visit us: tech.zalando.com

ZALANDO
TECHNOLOGY

500+
Apps
800+
Tech employees
August

Conway’s Law
“organizations which design systems
...are constrained to produce designs
which are copies of the
communication structures of these
organizations”

ARCHITECTURE
AN
ARCHITECTURE
FOR
INNOVATION

API FIRST
REST
SAAS
MICRO SERVICES
CLOUD
OPEN SOURCE

THE SHOP
MONOLITH

http://blog.codinghorror.com/new-programming-jargon/
We call it
“Jimmy”

Thousands of Java classes, undocumented features
Business logic on all layers (including the database)

MICROSERVICES

Internet
LB
SKIPPER
SKIPPER
SKIPPER
SKIPPER
JIMMY
MOSAIC
INNKEEPER
INNKEEPER
INNKEEPERLB
REST
APIs

HIGHLY AVAILABLE
0 DOWNTIME
RELIABLE
FAST

INNKEEPER
github.com/zalando/innkeeper

API FIRST
REST

FORMAL
SPECIFICATION
FOR
RESTful APIs
The World's Most Popular Framework for APIs.

REST RESOURCES
GET /routes
GET /routes/{id}
POST /routes
DELETE /routes/{id}
GET /updated-
routes/{id}

GOING
REACTIVE

MODEL DBCONTROLLER
BUFFERBUFFER
DB RecordsDTOsJSON
CLIENT
TRADITIONAL APPLICATION
HTTP Request Method Call SQL
Blocking IO

MODEL DBCONTROLLER
DB StreamDTOsJSON
CLIENT
REACTIVE APPLICATION
HTTP Request Method Call SQL
Non-Blocking IO
StreamStreamStream

Scala
Typesafe
Composable
Meet

Separation of I/0
Resilience
Reactive Streams
Meet

def routesModifiedSince(localDateTime: LocalDateTime):
DatabasePublisher[RouteRow] = {
}
val routesTable = TableQuery[RoutesTable]
val q = for {
routeRow <- routesTable
if (routeRow.createdAt > localDateTime
| routeRow.deletedAt > localDateTime)
} yield routeRow
db.stream {
q.result
}

Composable
Materializable
Reactive Streams
Meet
Streams

import akka.stream.scaladsl.Source
def findRoutesModifiedSince(localDateTime: LocalDateTime):
Source[Route, Unit] = {
}
Source(
).mapConcat(_.toList)
routesRepo.selectModifiedSince(localDateTime).mapResult { row =>
}
row.id.map { id =>
Route(
id = id,
route = row.routeJson.parseJson.convertTo[NewRoute],
row.createdAt,
row.deletedAt
)
}

val route =
path("hello") {
get {
complete {
<h1>Hello World</h1>
}
}
}
Meet
Http

object Main extends App {
}
implicit val system = ActorSystem("my-system")
implicit val materializer = ActorMaterializer()
val route = ...
val bindingFuture =
Http().bindAndHandle(route, "localhost", 8080)
...

Innkeeper’s AKKA HTTP Routes
val route =
path("updated-routes" / Rest) { lastModifiedString =>
get { complete(…) }
} ~ path("routes") {
get { complete(…) }
~ post { complete(…) }
} ~ path("routes" / LongNumber) { id =>
get { … }
~ delete { … }
}

path("routes") {
get {
complete {
HttpResponse(
)
}
}
}
entity = HttpEntity.Chunked(
MediaTypes.`application/json`,
chunkedStreamSource
)
val chunkedStreamSource =
jsonService.sourceToJsonSource(routesService.allRoutes)

def sourceToJsonSource[T](source: Source[T, Unit])
(implicit writer: JsonWriter[T]):
Source[ChunkStreamPart, ((Unit, Unit), Unit)] = {
val commaSeparatedRoutes: Source[ChunkStreamPart, Unit] =
source
.map(t => Some(t.toJson.compactPrint))
.scan[Option[ChunkStreamPart]](None)({
case (None, Some(sourceElement)) => Some(ChunkStreamPart(sourceElement))
case (_, Some(sourceElement)) => Some(ChunkStreamPart(s", $sourceElement"))
})
.mapConcat(_.toList)
Source.single(ChunkStreamPart("[")) ++
commaSeparatedRoutes ++
Source.single(ChunkStreamPart("]"))
}

SAAS

OAUTH

val route: RequestContext => Future[RouteResult] =
authenticationToken { token =>
authenticate(token, authService) { authenticatedUser =>
path("updated-routes" / Rest) { lastModifiedString =>
get {
hasOneOfTheScopes(authenticatedUser)(scopes.READ) {
...

import akka.http.scaladsl._
import akka.http.scaladsl.server.directives.HeaderDirectives._
trait OAuthDirectives {
def authenticationToken: Directive1[String] =
headerValue(optionalValue("authorization")) |
reject {
AuthenticationFailedRejection(
CredentialsMissing,
HttpChallenge("", "")
)
}
...

CLOUD

STUPS.IO

FROM zalando/openjdk:8u45-b14-5
MAINTAINER Team Spearheads <team-spearheads@zalando.de>
EXPOSE 8080
RUN mkdir -p /opt/innkeeper
ADD target/scala-2.11/innkeeper-assembly-0.0.1.jar
/opt/innkeeper/
WORKDIR /opt/innkeeper
ENTRYPOINT java $(java-dynamic-memory-opts) -Dinnkeeper.env=prod
-server -jar innkeeper-assembly-0.0.1.jar

docker:
sbt assembly
docker build -t innkeper:latest-SNAPSHOT .
docker-push:
docker push innkeper:latest-SNAPSHOT
docker-run:
docker run -p 8080:8080 -t innkeper:latest-SNAPSHOT
test-db:
docker run -e POSTGRES_PASSWORD=innkeeper-test -e POSTGRES_USER=innkeeper-test
-p 5433:5432 postgres:9.4
tick:
senza create senza.yaml tick latest-SNAPSHOT
tock:
senza create senza.yaml tock latest-SNAPSHOT

OPEN
SOURCE

github.com/zalando/innkeeper

DO
OSF

RADICAL AGILITY
TRUST
INSTEAD OF CONTROL

# use Docker-based container (instead of OpenVZ)
sudo: false
cache:
directories:
- $HOME/.sbt
- $HOME/.ivy2
language: scala
script:
- sbt ++$TRAVIS_SCALA_VERSION test
- sbt ++$TRAVIS_SCALA_VERSION it:test
# Trick to avoid unnecessary cache updates
- find $HOME/.sbt -name "*.lock" | xargs rm
scala:
- 2.11.7
jdk:
- oraclejdk8
addons:
postgresql: "9.4"
before_script:
- psql -c 'CREATE ROLE innkeepertest superuser login createdb;' -U postgres
- psql -c 'CREATE DATABASE innkeepertest;' -U postgres

NEXT
STEPS

APPLICATION LOGS: SCALYR

TODO: Screenshot
ZMON

Where to Find Us:
Tech Blog: tech.zalando.com
GitHub: github.com/zalando
Innkeeper: github.com/zalando/innkeeper
Twitter: @ZalandoTech
Instagram: zalandotech
Jobs: http://tech.zalando.com/jobs

THANK YOU!
QUESTIONS?