Docker and Puppet
Containerization is the new virtualization

What's this all
about?

What is Docker?

Container
virtualization

Build, ship, run

Build once.

Run in many
places.

Isolated, layered,
standard and
content agnostic

But this isn't
new?!!?

So why should I care?
Software delivery mechanism - a bit like a package!
Put your application in a container, run it anywhere
A bit like a VM but ...

Caring
Containers boot faster
Containers have less overhead
Containers bring native performance
Containers are Cloud & VM-compatible

Docker Basics
Image & Dockerfile
The Docker Hub
Container

Building Docker images
FROM ubuntu
MAINTAINER James Turnbull "james@example.com"
RUN apt-get -qqy update
RUN apt-get install -qqy apache2
ADD index.html /var/www/
ENV APACHE_RUN_USER www-data
ENV APACHE_RUN_GROUP www-data
ENV APACHE_LOG_DIR /var/log/apache2
EXPOSE 80
ENTRYPOINT ["/usr/sbin/apache2"]
CMD ["-D", "FOREGROUND"]

Building the image
$ sudo docker build -t="jamtur01/apache2" .

Sharing the image
$ sudo docker push jamtur01/apache2

Running the container
$ sudo docker run -ti -p 80:80 jamtur01/apache2

Docker and
Puppet

So does the
Dockerfile solve
all?

Well sorta...
It depends.

Doesn't have to deal with low-level stuff
Doesn't have to converge
Rebuilds are fast and cached
Allows inheritance and composition
Easy learning curve

But...

Doesn't deal with low-level stuff
Doesn't define resource dependencies
Doesn't define what runs when

Dockerfile
versus
Shell script

Shell scripts
Okay for simple stacks
Imperative
Rarely idempotent

Dockerfile
versus
Configuration
Management

The Good
Handles low-level stuff
Abstracts details
Ensures convergence to a known state
Library of reusable, composable
templates

The Bad
Steep learning curve
Generally requires a trigger
Resource-intensive

Digging and fixing,
Having so much fun
Working together,
They get the job done

Before
Use Puppet to setup hardware,
install packages, deploy code, run
services.
After
Use Puppet to setup hardware,
install Docker, run containers.
Use Dockerfiles to install
packages, deploy code, run
services.

Install Docker
with Puppet

Should I run
Puppet in my
containers?

Nope!

Should I use
Puppet to build
my images?

Yep!

Deploying a
Puppet-powered
container

Puppet Apply
FROM ubuntu:14.04
MAINTAINER James Turnbull "james@example.com"
RUN apt-get -qqy update
RUN apt-get -qqy install rubygems
RUN gem install --no-ri --no-rdoc puppet
RUN mkdir /puppet
WORKDIR /puppet
ADD site.pp /puppet/site.pp
RUN puppet apply site.pp

Librarian Puppet
FROM ubuntu:14.04
MAINTAINER James Turnbull "james@example.com"
RUN apt-get -y -q install wget git-core rubygems
RUN gem install --no-ri --no-rdoc puppet librarian-puppet
ADD Puppetfile /
RUN librarian-puppet install
RUN puppet apply --modulepath=/modules -e "class { 'nginx': }"
RUN echo "daemon off;" >> /etc/nginx/nginx.conf
EXPOSE 80
CMD ["nginx"]

But there's more!

What if we could get rid of...
SSHd - Access via nsenter or docker exec
Crond in a container
Logging in a container

Creates a new
architecture

Separates orthogonal concerns
Don't rebuild your app to change services
Have different policies in domains
Ship lighter apps