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.

The last two months have been busy as I am writing the O'Reilly Docker cookbook at night and on week-ends. CloudStack during the day, Docker at night :) You can read the very "drafty" preface on Safari and you will get a sense of why I started writing the book.

Docker is amazing, it brings a terrific user experience to packaging application and deploying them easily. It is also a software that is moving very fast with over 5,500 pull requests closed so far. The community is huge and folks are very excited about it, just check those 18,000+ stars on Github.

Writing a book on Docker means reading all the documentation, reading countless blogs that are flying through twitter and then because its a cookbook, you need to get your hands dirty and actually try everything, test everything, over and over again. A cookbook is made of recipes in a very set format: Problem, Solution, Discussion. It is meant to be picked up at anytime, opened at any page and read a recipe that is independent of all the others. The book is now on pre-release, it means that you can buy it and get the very drafty version of the book as I write it, mistakes, typos and bad grammar included. As I keep writing you get the updates and once I am done you of course get the final proof-read, corrected and reviewed version.

As I started writing, I thought I would share some of the snippets of code I am writing to do the recipes. The code is available on GitHub at the how2dock account. How2dock should become a small company for Docker training and consulting as soon as I find spare time :).

What you will find there is not really code, but really a repository of scripts and Vagrantfiles that I use in the book to showcase a particular feature or command of Docker. The repository is organized the same way than the book. You can pick a chapter and then a particular recipe then go through the README.

For instance if you are curious about Docker swarm:

$ git clone https://github.com/how2dock/docbook.git
$ cd ch07/swarm
$ vagrant up

This will bring up four virtual machines via Vagrant and do the necessary boostrapping to get the cluster setup with Swarm.

If you want to run a wordpress blog with a mysql database, checkout the fig recipe:

$ cd ch07/fig
$ vagrant up
$ vagrant ssh
$ cd /vagrant
$ fig up -d

And enjoy Wordpress :)

I put a lot more in there. You will find an example of using the Ansible Docker module, a libcloud script to start an Ubuntu Snappy instance on EC2, a Dockerfile to help you create TLS certificates (really a convenience container for testing TLS in Docker). A Docker machine setup and a recipe on using Supervisor.

As I keep writing, I will keep putting all the snippets in this How2dock repo. Except frequent changes, typos, errors...and corrections :)

And FWIW, it is much scarier to put a book out in pre-release unedited than to put some scripts up on GitHub.

Suggestions, comments, reviews all welcome ! Happy Docking !