Docker, Marathon, Mesos, Ubuntu

Managing Docker Clusters Using Mesos and Marathon

Docker has became one of my favourite tool. It’s super cool and super easy tool to manage linux containers. LXC’s are around in IT world for some time, but by the entry of Docker last year, the wave started rising. Thanks to Docker team and Solomon Hykes for open sourcing such a wonderfull project. I’ve already mentioned a lot of stuffs about Docker in my previos blogs, so today im going explain how Docker can be used as a Cluster. There are some interesting tools like CoreOS, Helios etc for managing Docker as a cluster. But today i’m going to explain on how to set up a Docker cluster using Apache Mesos. CoreOS is a custom linux os which comes with SystemD. But the restriction is, we have to use that custom images of coreos.. Indeed CoreOS team open sourced some exciting tools like etcd fleet which works with CoreOS for managing Docker clusters. But Mesos is quite simple, we can install it via package, or even using tar balls available in thier Github repo onto most of the Linux Distro’s and it’s quite easy to configure also. Mesos is heavily used by Twitter to manage their data center’s. And now Mesosphere has opensourced a new tool called Mararthon which now provides a UI and a Rest API for maaging and scheduling Mesos Frameworks aka jobs, in this case containers as a service.

A few weeks ago, Mesos 0.19 was released which comes with an official support for Docker coantiners by intergrating Deimos into it. And a few days ago Marathon has released their new version 0.6.0 supports launching any task in a Docker container via Mesos 0.19+

Setting up Mesos Cluster

In this test setup, i’m going to setup both Mesos master/slave and Zookeeper on the same Ubuntu 14.04 vagrant node. First we can install the dependencies,

$ apt-get install curl python-setuptools python-pip python-dev python-protobuf

Now we can install Zookeeper

$ apt-get install zookeeperd

After the installation, ZooKeeper has 1 configuration. Each Zookeeper needs to know its position in the quorum.

$ echo 1 | sudo dd of=/var/lib/zookeeper/myid

Now we can setup Docker

$ echo "deb docker main" > /etc/apt/sources.list.d/docker.list

$ apt-get update && apt-get install lxc-docker

$ docker version

   Client version: 1.0.0
   Client API version: 1.12
   Go version (client): go1.2.1
   Git commit (client): 63fe64c
   Server version: 1.0.0
   Server API version: 1.12
   Go version (server): go1.2.1
   Git commit (server): 63fe64c

Let’s pull some basic ubuntu images from Docker Hub so that we can use the same for testing.

$ docker pull libmesos/ubuntu

Now we can configure Mesos

$ curl -fL -o /tmp/mesos.deb

$ dpkg -i /tmp/mesos.deb

$ mkdir -p /etc/mesos-master

$ echo in_memory | sudo dd of=/etc/mesos-master/registry

## Mesos Python egg for use in authoring frameworks

$ curl -fL -o /tmp/mesos.egg

$ easy_install /tmp/mesos.egg

We can download the latest Marathon 0.6 from here

$ tar xvzf marathon-0.6.0.tgz

Mesos uses Deimos for managing dockers, Deimos can installed via pip

$ pip install deimos

Also, we need to configure mesos to use Deimos,

$ mkdir -p /etc/mesos-slave

$ echo /usr/local/bin/deimos | sudo dd of=/etc/mesos-slave/containerizer_path

$ echo external | sudo dd of=/etc/mesos-slave/isolation

Now we can start all the services.

$ initctl reload-configuration

$ service docker start

$ service zookeeper start

$ service mesos-master start

$ service mesos-slave start

##### Starting Marathon #####

$ cd marathon-0.6.0

$ ./bin/start --master zk://localhost:2181/mesos --zk_hosts localhost:2181

Marathon will now start listening to port 8080, We can access the UI from the browser via this port, also via rest API using the same port.

curl localhost:8080/help   # gives us some details about the API's

I just went through the Deimos code, so under the hood they are using docker run with some default parameters like --sig-proxy, --rm, --cidfile, -v, -w and extra parameters that we are passing while creating the task via Marathon.

As of now, we still can’t pass details like Container image, Docker options via Marathon GUI. So we can use the Rest API for the time being. Below is a sample curl request for launcing a single container,

curl -X POST -H "Accept: application/json" -H "Content-Type: application/json" \
    localhost:8080/v2/apps -d '{
        "container": {"image": "docker:///libmesos/ubuntu", "options": ["--privileged"]},
        "cpus": 0.5,
        "cmd": "sleep 500",
        "id": "docker-tester",
        "instances": 1,
        "mem": 300

We can pass custom options to the docker run command via “options”. After making the curl request, we can check the syslog, as mesos will be logging into syslog by default. We can even see the Docker run command on the same.

Jun 27 07:24:58 vagrant-ubuntu-trusty-64 deimos[19227]: deimos.containerizer.docker.launch() exit 0 // docker run --sig-proxy --rm --cidfile /tmp/deimos/mesos/00d459fb-22ca-4af7-9a97-ef8a510905f2/cid -w /tmp/mesos-sandbox -v /tmp/deimos/mesos/00d459fb-22ca-4af7-9a97-ef8a510905f2/fs:/tmp/mesos-sandbox --privileged -p 31498:31498 -c 512 -m 300m -e PORT=31498 -e PORT0=31498 -e PORTS=31498 libmesos/ubuntu sh -c 'sleep 500'

We can also use the Marathon Rest API to check the status of the job which we started.

curl -X GET -H "Content-Type: application/json" localhost:8080/v2/apps

Below is the screenshort for the same from the Marathon UI.

We can also check if the container is launched via docker ps command.

A more detailed report about the Docker job which we have launched can be viewed via the default Mesos GUI listening on port 5050 on the Mesos master. Now we can test the scalability of the Job. Currently we have only one container running. So now we can try scaling say adding one more node. We can do it in two ways, like via PUT request using curl or using GUI

curl -X PUT -H "Content-Type: application/json" localhost:8080/v2/apps/docker-tester \
    "container": {"image": "docker:///libmesos/ubuntu", "options": ["--privileged"]},
            "cpus": 0.5,
            "cmd": "sleep 500",
            "id": "docker-tester",
            "instances": 2,     # increasing the instance count to 2
            "mem": 300

Now we can use the docker ps command to see if the new container is launched or not. Also we can see that status in UI also.

Similarly, we can scale down also. I’ve tested the same and all seems to be good. Marathon ensures that the docker process will be running. So incase if the process crashes Marathon will restart the same and ensures that the instances are up and running as per our configuration. There are a few other Open Sourced Mesos Scheduler’s like Apache Aurora, Airbnb’s Chronos. But for my requirement marathon is pretty straight and simple and also provides a very good Rest API layer for managing containers. Mesos, Marathon and Docker are still young, but provides a killer combination for managing clusters built over Docker containers.


4 thoughts on “Managing Docker Clusters Using Mesos and Marathon

  1. Pingback: Managing HA Docker Cluster Using Multiple Mesos Masters | beingasysadmin

  2. Pingback: Running Mesos With Native Docker Support | beingasysadmin

  3. Pingback: Running Mesos With Native Docker Support - 小Q

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