Chaos

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.

Why yet another framework?

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.

Design Goals

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

Building Blocks

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

Getting Started

Requirements

• JDK 1.8+
• SBT 0.13.x+

Example App

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

Built in Endpoints

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

Using Chaos in your Project

Chaos releases are available from Mesosphere's Maven repository.

Maven

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>

SBT

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"
)

Getting Help

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

Authors

• Tobias Knaup
• Florian Leibert

Current Users

• Chronos, a fault tolerant job scheduler that handles dependencies and ISO8601 based schedules.