A lightweight framework for writing REST services in Scala.

Chaos (Greek χάος, khaos) refers to the formless or void state preceding the creation of the universe or cosmos in the Greek creation myths. Chaos (the framework) precedes creation of a universe of services.

At Mesosphere we're building REST services in Scala, and we wanted a solid foundation. We had experience with Dropwizard and Twitter Commons, which are both great Java frameworks, but are a bit hard to use from Scala. We also experimented with Play!, but it does many things besides REST, which adds unnecessary baggage.

We wanted a framework that

• is easy to use
• does one thing really well (REST)
• feels good in Scala
• is built on battle-tested and well-supported libraries
• doesn't try to reinvent the wheel

There are great JVM libraries for every part of a REST stack. Chaos just glues these together.

• Jersey for REST via annotations
• Guava for lifecycle management and various utilities
• Jetty as the web server and servlet container
• Jackson for JSON support
• Coda Hale's Metrics for JVM and application metrics

• JDK 1.8+
• SBT 0.13.x+

There is an example app in [src/main/scala/mesosphere/chaos-examples/] (https://github.com/mesosphere/chaos/blob/master/chaos-examples/src/main/scala/mesosphere/chaos/examples/Main.scala). To run the example:

sbt run

Make requests to the example endpoints with HTTPie:

http localhost:8080/persons
http localhost:8080/persons name=Bunny age=42

• /ping - health check.
• /metrics - metrics as JSON
• /logging - configure log levels at runtime

Chaos releases are available from Mesosphere's Maven repository.

To add Chaos to a Maven project, add this to your pom.xml:

<properties>
    <chaos.version>0.5.2</chaos.version>
</properties>

...

<repositories>
    <repository>
        <id>mesosphere-public-repo</id>
        <name>Mesosphere Public Repo</name>
        <url>http://downloads.mesosphere.io/maven</url>
    </repository>
</repositories>

...

<dependencies>
    <dependency>
        <groupId>mesosphere</groupId>
        <artifactId>chaos</artifactId>
        <version>${chaos.version}</version>
    </dependency>
</dependencies>

To add Chaos to an SBT project, add this to your build.sbt:

resolvers += "Mesosphere Public Repo" at "http://downloads.mesosphere.io/maven"

libraryDependencies ++= Seq(
  "mesosphere" % "chaos" % "0.5.2",
  "com.sun.jersey" % "jersey-bundle" % "1.17.1"
)

If you have questions, please post on the Chaos Users Group email list. The team at Mesosphere is also happy to answer any questions.

• Tobias Knaup
• Florian Leibert

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