1 Command to Mesos with Docker Compose

If you have not tried Docker, you should. The sheer power it puts in your hands and the simplicity of the user experience will just wow you. In this post, I will show you how to start a one node Mesos setup with Docker compose.

Docker announced compose on February 26th. Compose allows you to describe a multi-container setup and manage it with one binary docker-compose. The containers and volumes combinations managed by Compose are defined in a YAML file, super easy to read and super easy to write. The UX is very similar to the Docker CLI.

When compose was released, I tried it and was a bit underwhelmed, as it is basically a relooking of Fig. This is not unexpected as Docker Inc, acquired Orchard the makers of Fig. But I was expecting more added functionality and even a tighter integration with the Docker client (something a dev branch actually prototyped), even a common release instead of a separate binary. I am sure this will come.

As I am writing the docker cookbook, I have deployed Wordpress 20 different ways, and it's getting a bit boring !  I was looking for more information on Mesos and its support for Docker, I re-read a terrific blog post that showed how to start a Mesos setup (zookeeper, master, slave, marathon framework) in 7 commands. Can't beat that.

When I re-read this post, I automatically thought this was an exciting use case for docker-compose. One YAML file to start Mesos/Zookeeper/Marathon and experiment with it. Of course I am not talking about a production multi-node setup. I am just looking at it for an easy Mesos experiment.
I will spare you the details of installing compose (just a curl away). The dockers docs are great.

So here is the YAML file describing our Mesos setup:

zookeeper:
  image: garland/zookeeper
  ports:
   - "2181:2181"
   - "2888:2888"
   - "3888:3888"
mesosmaster:
  image: garland/mesosphere-docker-mesos-master
  ports:
   - "5050:5050"
  links:
   - zookeeper:zk
  environment:
   - MESOS_ZK=zk://zk:2181/mesos
   - MESOS_LOG_DIR=/var/log/mesos
   - MESOS_QUORUM=1
   - MESOS_REGISTRY=in_memory
   - MESOS_WORK_DIR=/var/lib/mesos
marathon:
  image: garland/mesosphere-docker-marathon
  links:
   - zookeeper:zk
   - mesosmaster:master
  command: --master zk://zk:2181/mesos --zk zk://zk:2181/marathon
  ports:
   - "8080:8080"
mesosslave:
  image: garland/mesosphere-docker-mesos-master:latest
  ports:
   - "5051:5051"
  links:
   - zookeeper:zk
   - mesosmaster:master
  entrypoint: mesos-slave
  environment:
   - MESOS_HOSTNAME=192.168.33.10
   - MESOS_MASTER=zk://zk:2181/mesos
   - MESOS_LOG_DIR=/var/log/mesos
   - MESOS_LOGGING_LEVEL=INFO

Four containers, images pulled from Docker hub, some ports exposed on the host. Some container linking and some environment variables used to configure the Mesos slave and master. One small hickup in the Slave defintion. You will see that I set the MESOS_HOSTNAME to the IP of the host. This allows me to browse the stdout and stderr of a Marathon task, otherwise we cannot reach it easily (small improvement to be done there.)

Launch this with docker-compose:

$ ./docker-compose up -d
Recreating vagrant_zookeeper_1...
Recreating vagrant_mesosmaster_1...
Recreating vagrant_marathon_1...
Recreating vagrant_mesosslave_1...

And open your browser at http://IP_HOST:5050 then follow the rest of the blog to start a task in marathon.

Bottom line, I went from '7 commands to Mesos' to '1 command to Mesos' thanks to Docker-compose and a fairly simple YAML file. Got to love it. When compose can do this across Docker hosts in a Docker Swarm started by Machine. Then the real fun will begin !

Rancher on RancherOS

Someone at Rancher must have some cattle in the middle of Arizona or in the backcountry of California. Or one of their VCs might be in Montana sitting in a big ranch while Docker is eating the IT world. In any case, this post is short and sweet like veggies and not like cattle (TFW) and is about Rancher and the newly announced RancherOS. Check out the rancheros announcement.

Let's keep this short, shall we ? Docker is great, but it is a daemon running on a single host. Since you want to scale :) and operate multiple servers, you need something to manage your Docker containers across multiple hosts. Several solutions are emerging, of course Docker Swarm but also Kubernetes, Lattice from Cloudfoundry and even Apache Mesos. Rancher is one of these cluster management solutions for Docker. It does some nice things like cross-hosts container linking through a custom built network overlay (think Flannel, Weave, Socketplane).

You can use Rancher with any set of Docker hosts. However, a new type of operating systems have started to appear. Container optimized OS. Or Just Enough Operating System for Docker. CoreOS, ProjectAtomic from RedHat, Ubuntu Snappy fit in that space. They aim to provide rolling atomic upgrades to the OS and run everything in it as a container. No more package manager, magic happens and you are always up to date. Package all your apps in containers, and use Rancher to run them in your cluster. End of story. Wait, enters rancherOS.

RancherOS

A couple lines of bash make all the talking:

$ git clone https://github.com/rancherio/os-vagrant.git
$ cd os-vagrant
$ vagrant up
$ vagrant ssh
[rancher@rancher ~]$ docker version
Client version: 1.5.0
…

rancherOS is a super minimalistic OS exclusively for Docker. It goes further and also runs system services as container themselves. And I will let @ibuildthecloud talk about systemd and Docker as PID 1.

[rancher@rancher ~]$ sudo system-docker ps
CONTAINER ID        IMAGE               COMMAND                ...      NAMES
32607470eb78        console:latest      "/usr/sbin/console.s   ...      console             
d0420165c1c0        userdocker:latest   "/docker.sh"           ...      userdocker          
375a8de12183        syslog:latest       "/syslog.sh"           ...      syslog              
d284afd7f628        ntp:latest          "/ntp.sh"              ...      ntp   

The next logical question is of course....drum roll... Can I run rancher on rancheros. RinR not R&R ? And the answer is a resounding yes. I expect Rancher to come out in the next weeks maybe months with a solid product based on the two.

Rancher

If you are interested to try out RinR then check out the Ansible playbook I just made. You can use use it to deploy a cluster of rancherOS instances in AWS, and use one of them as a master and the others as workers. The master runs in a container:

$ docker run -d -p 8080:8080 rancher/server 

And the workers can register with their agent:

$ sudo docker run --rm -it --privileged -v /var/run/docker.sock:/var/run/docker.sock rancher/agent http://<master_ip>:8080

Once all the workers have registered you can use the UI or the API to start containers.

As you can see I tested this at web scale with two nodes :)

Notes

In this very early super bleeding-edge testing phase (as you can tell in my good spirit today), I did find a few things that were a bit strange. Considering rancherOS was announced just last week, I am sure things will get fixed. Cloud-init support is minimal, not able to add second network interface, support for both keypair and userdata at the same time seems off. The UI was a bit slow to start and building the overlay was also a bit slow. It is also possible that I did something wrong.

Overall though, rancher is quite nice. It builds on years of experience in the team with developing CloudStack and operating clouds at scale and applies it to the Docker world. It does seem that they want to integrate with and provide the native Docker API, this would mean that users will be able to use Docker machine to add hosts to a rancher cluster, or even Docker swarm and that launching a container would also be a docker command away. How that differentiates from Swarm itself is not yet clear, but I would bet we will see additional networking and integration services in Rancher. Blurring the lines with Kubernetes ? Time will tell.