Marathon

Marathon is a Mesos framework for long-running applications. Given that you have Mesos running as the kernel for your datacenter, Marathon is the init or upstart daemon.

Marathon provides a REST API for starting, stopping, and scaling applications. Marathon is written in Scala and can run in highly-available mode by running multiple copies of Marathon. The state of running tasks gets stored in the Mesos state abstraction.

Try Marathon now on Elastic Mesos.

Go to the interactive Marathon tutorial that can be personalized for your cluster.

Marathon is a meta framework: you can start other Mesos frameworks such as Chronos or Storm with it to ensure they survive machine failures. It can launch anything that can be launched in a standard shell. In fact, you can even start other Marathon instances via Marathon.

Features

• HA -- run any number of Marathon schedulers, but only one gets elected as leader; if you access a non-leader, your request gets proxied to the current leader
• Basic Auth and SSL
• REST API
• Web UI
• Metrics -- via Coda Hale's metrics library
• Constraints -- e.g., only one instance of an application per rack, node, etc. See the documentation for more info.
• Service Discovery and Load Balancing -- see the documentation for more info.
• Event Subscription -- e.g., if you need to notify an external web service about task updates or state changes, you can supply an HTTP endpoint to receive notifications. See the wiki page for details.

Overview

The graphic shown below depicts how Marathon runs on top of Mesos together with the Chronos framework. In this case, Marathon is the first framework to be launched and it runs alongside Mesos. In other words, the Marathon scheduler processes were started outside of Mesos using init, upstart, or a similar tool. Marathon launches two instances of the Chronos scheduler as a Marathon task. If either of the two Chronos tasks dies -- due to underlying slave crashes, power loss in the cluster, etc. -- Marathon will re-start a Chronos instance on another slave. This approach ensures that two Chronos processes are always running.

Since Chronos itself is a framework and receives Mesos resource offers, it can start tasks on Mesos. In the use case shown below, Chronos is currently running two tasks. One dumps a production MySQL database to S3, while another sends an email newsletter to all customers via Rake. Meanwhile, Marathon also runs the other applications that make up our website, such as JBoss servers, a Jetty service, Sinatra, Rails, and so on.

The next graphic shows a more application-centric view of Marathon running three applications, each with a different number of tasks: Search (1), Jetty (3), and Rails (5).

As the website gains traction and the user base grows, we decide to scale-out the search service and our Rails-based application. This is done via a simple REST call to the Marathon API to add more tasks. Marathon will take care of placing the new tasks on machines with spare capacity, honoring the constraints we previously set.

Imagine that one of the datacenter workers trips over a power cord and a server gets unplugged. No problem for Marathon, it moves the affected search service and Rails tasks to a node that has spare capacity. The engineer may be temporarily embarrased, but Marathon saves him from having to explain a difficult situation!

Setting Up And Running Marathon

Requirements

• Mesos 0.15.0+
• Zookeeper
• JDK 1.6+
• Scala 2.10+
• Maven 3.0+

Installation

1. Install Mesos. One easy way is via your system's package manager. Current builds for major Linux distributions and Mac OS X are available from Mesosphere on their downloads page.

   If building from source, see the Getting Started page or the Mesosphere tutorial for details. Running make install will install Mesos in /usr/local in the same way as these packages do.

2. Check out Marathon and use Maven to build a JAR:

    mvn package
   

3. Run ./bin/build-distribution to package Marathon as an executable JAR (optional).

Compiling Assets

Note: You only need to follow these steps if you plan to edit the JavaScript source.

1. Install NPM

2. Change to the assets directory

    cd src/main/resources/assets
   

3. Install dev dependencies

    npm install
   

4. Build the assets

    ./bin/build
   

The main JS file will be written to src/main/resources/assets/js/dist/main.js.

Running in Production Mode

To launch Marathon in production mode, you need to have both Zookeeper and Mesos running. The following command launches Marathon on Mesos in production mode. Point your web browser to localhost:8080 and you should see the Marathon UI.

./bin/start --master zk://zk1.foo.bar:2181/mesos,zk2.foo.bar:2181/mesos --zk_hosts zk1.foo.bar:2181,zk2.foo.bar:2181

Note the different format of the --master and --zk_hosts options. Marathon uses --master to find the Mesos masters, and --zk_hosts to find Zookeepers for storing state. They are separate options because Mesos masters can be discovered in other ways as well.

Running in Development Mode

Mesos local mode allows you to run Marathon without launching a full Mesos cluster. It is meant for experimentation and not recommended for production use. Note that you still need to run Zookeeper for storing state. The following command launches Marathon on Mesos in local mode. Point your web browser to http://localhost:8080, and you should see the Marathon UI.

./bin/start --master local --zk_hosts localhost:2181

Working on assets

When editing assets like CSS and JavaScript locally, they are loaded from the packaged JAR by default and are not editable. To load them from a directory for easy editing, set the assets_path flag when running Marathon:

./bin/start --master local --zk_hosts localhost:2181 --assets_path src/main/resources/assets/

Configuration Options

• MESOS_NATIVE_LIBRARY: bin/start searches the common installation paths, /usr/lib and /usr/local/lib, for the Mesos native library. If the library lives elsewhere in your configuration, set the environment variable MESOS_NATIVE_LIBRARY to its full path.

  For example:

  MESOS_NATIVE_LIBRARY=/Users/bob/libmesos.dylib ./bin/start --master local --zk_hosts localhost:2181
  

Run ./bin/start --help for a full list of configuration options.

REST API Usage

The full API documentation shows details about everything the Marathon API can do.

Example using the V2 API

# Start an app with 128 MB memory, 1 CPU, and 1 instance
curl -X POST -H "Accept: application/json" -H "Content-Type: application/json" \
    localhost:8080/v2/apps \
    -d '{"id": "app_123", "cmd": "sleep 600", "instances": 1, "mem": 128, "cpus": 1}'

# Scale the app to 2 instances
curl -X PUT -H "Accept: application/json" -H "Content-Type: application/json" \
    localhost:8080/v2/apps/app_123 \
    -d '{"instances": 2}'

# Stop the app
curl -X DELETE localhost:8080/v2/apps/app_123

Example starting an app using constraints

# Start an app with a hostname uniqueness constraint
curl -X POST -H "Accept: application/json" -H "Content-Type: application/json" \
    localhost:8080/v2/apps \
    -d '{"id": "constraints", "cmd": "hostname && sleep 600", "instances": 10, "mem": 64, "cpus": 0.1, "constraints": [["hostname", "UNIQUE", ""]]}'

The V1 API (Deprecated)

The V1 API was deprecated in Marathon v0.4.0 on 2014-01-24 but continues to work as it did before being deprecated. Details on the V1 API can be found in the API documentation.

Marathon Clients

• Ruby gem and command line client

  Running Chronos with the Ruby Marathon Client:

    marathon start -i chronos -u https://s3.amazonaws.com/mesosphere-binaries-public/chronos/chronos.tgz \
        -C "./chronos/bin/demo ./chronos/config/nomail.yml \
        ./chronos/target/chronos-1.0-SNAPSHOT.jar" -c 1.0 -m 1024 -H http://foo.bar:8080
  

• Scala client, developed at Guidewire

• Java client by Mohit Soni

Help

If you have questions, please post on the Marathon Framework Group email list. You can find Mesos support in the #mesos channel on freenode (IRC). The team at Mesosphere is also happy to answer any questions.

Contributors

Marathon was written by the team at Mesosphere that also developed Chronos, with many contributions from the community.

• Tobias Knaup
• Ross Allen
• Florian Leibert
• Harry Shoff
• Brenden Matthews
• Jason Dusek
• Thomas Rampelberg
• Connor Doyle