Docker and Puppet

Containerization is the new virtualization

who

• engineer and operations chap
• open source chap
• funny accent

The Docker Book

www.dockerbook.com

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PUPPETCONFLOVESDOCKER

Who are you folks?

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

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

The Future

What if we could...

• Run the Puppet agent outside of the container

• Run a single agent for many containers

• Share the cost of the agent

Questions?