pombredanne / marathon

An Apache Mesos framework for long-running services.

Marathon

Marathon is a Mesos framework for long-running services. Given that you have Mesos running as the kernel for your datacenter, Marathon is the init or upstart daemon. It was written by the team that also developed Chronos.

Marathon provides a REST API for starting, stopping, and scaling services. There is also a Ruby command line client. Marathon is written in Scala and can run in highly-available mode by running multiple Marathon instances. The state of running tasks gets stored in the Mesos state abstraction. Features are listed below.

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. It can launch anything that can be launched in a standard shell. In fact, you can even start other Marathon instances via Marathon.

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.

Authors

• Tobias Knaup
• Florian Leibert
• Harry Shoff
• Jason Dusek

Requirements

• Mesos 0.14.0+
• Zookeeper
• JDK 1.6+
• Scala 2.10+
• Maven 3.0+

Features

• HA -- run any number of Marathon schedulers, but only one gets elected as leader; if you access a non-leader, you get an HTTP redirect to the current leader
• Basic Auth and SSL
• REST API
• Web UI
• Metrics -- via Coda Hale's metrics library
• Service Constraints -- e.g., only one instance of a service per rack, node, etc.
• Service Discovery and Monitoring
• Event Subscription -- e.g., if you need to notify an external service about task updates or state changes, you can supply an HTTP endpoint to receive notifications

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 an 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 services required for the web app, in general.

The next graphic shows a more application-centric view of Marathon running three tasks: Search, Jetty, and Rails.

As the website gains traction and the user base grows, we decide to scale-out the search and Rails-based services.

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 instance 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

First, 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. Using make install will install Mesos in /usr/local in the same way as these packages do.

To create a Jar for Marathon, checkout the sources and use Maven to build it:

mvn package

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/mesos,zk2.foo.bar/mesos --zk_hosts zk1.foo.bar,zk2.foo.bar

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.

Local 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 ./path/to/assets

Configuration Options

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

Example API Usage

Using HTTPie:

http localhost:8080/v1/apps/start id=sleep cmd='sleep 600' instances=1 mem=128 cpus=1
http localhost:8080/v1/apps/scale id=sleep instances=2
http localhost:8080/v1/apps/stop id=sleep

Using Marathon Client, the following runs Chronos:

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