Why everyone is excited about Docker (and you should too...)

1. MILAN november 28th/29th 2014
Carlo Bonamico
Why everyone is excited about Docker
(and you should too...)
carlo.bonamico@nispro.it - NIS s.r.l.
carlo.bonamico@gmail.com – Genova Java User Group
Twitter: @carlobonamico

2. Didn't you hear these at least once?
 Can you deploy my application? It's for Linux...
 Yes, but which distribution? release? patch?
 Why the deploy failed? Didn't you test the app?
 Yes, but the production environment is slightly different
 The new version is having some issues, can you
rollback to the previous one, please?
 Yes, but it will take some hours – if John hasn't already
gone home – in that case he'll do it on monday
 Can you debug this production problem?
 Yes, but I need an hosted DEV environment as I can't
run all the needed VMs on my laptop

3. In the beginning...
 We moved from
physical server to VMs
 performance and
resource usage issues
 Got more security and
hardware
independence
 but creating a VM
still takes time
 Some hosting / cloud
providers took
advantage of kernel-level
virtualization
 LXC
 OpenVZ
 But out-of-reach of the
common man Dev
 Try setting up LXC...

4. Then in 2013 (please fake drum roll)
 Solomon Hykes (@solomonstre) started Docker as
an internal project within dotCloud.com hosting
 to make Linux Containers an order of magnitude easier
 and more powerful, too
 Open Sourced in March 2013
 in a week, it went to the top projects on GitHub
 https://github.com/docker/docker
 A catalyst for innovative work on containers
 shortly, several other key projects converged

5. Fast Forward to mid-2014
 Major Open Source project with contributions from
all the big names in IT
 Google, RedHat, OpenShift, Ubuntu ...
 DotCloud → Docker Inc.
 https://www.docker.com/
 All cloud big and small names are in a rush to
provide Docker hosting
 Amazon, CloudFoundry, Linode, Digital Ocean…
 and Microsoft !
 both for Azure and soon for the new Windows Server...

6. But why should I join the party?
 In short, Docker makes creating
 Development
 Test
 and Production
 environments an order of magnitude
 simpler
 faster
 and completely portable
 across both local and cloud infrastructure

7. Docker hello world...
 What's happening here?
user@laptop:~$ docker pull ubuntu:14.04.1
user@laptop:~$ docker run ubuntu:14.04.1 echo "Hello
World"
Hello World
 And here?
user@laptop:~$ docker run ­t
­i
ubuntu:14.04.1
/bin/bash
root@d1fa8fcb4518:/# ls
bin boot dev etc home lib lib64 media mnt
opt proc root run sbin srv sys tmp usr var
root@d1fa8fcb4518:/# python
bash: python: command not found
root@d1fa8fcb4518:/#

8. Behind the scenes...
 I run the docker cli (Command Line Interface )
user@laptop:~$ docker run ­t
­i
ubuntu:14.04.1
/bin/bash
 the CLI connects to docker daemon by REST API,
 which asks the Linux kernel to create a new container
d1fa8fcb4518
 and runs /bin/bash in it, so
root@d1fa8fcb4518:/# ls
bin boot dev etc home lib lib64 media ...
 lists the filesystem of the container (!= from host OS)
root@d1fa8fcb4518:/# python
bash: python: command not found

9. So what's inside Docker?
 Isolation layer based on kernel namespaces
 separate process trees, network, user IDs and mounted
file systems
 Resource isolation through cgroups
 CPU, memory, block I/O and network
 Standard interface through libcontainer
 based on libvirt, LXC and systemd-nspawn
 And more...

10. How are data & containers stored?
 AUFS Another Union Filesystem
 possibly other snapshotting fs (zfs) / block device (LVM)
 Layered approach
 rootfs → kernel layer
 bootfs → a Linux distribution
 emacs
 apache
 application
 Copy-on-Write approach – à la subversion (SVN)

11. Containers, Images and Index
 A Container is a running instance
 can run 100-1000 containers per host
 An Image is a static snapshot
 in turn based on a series of layers
 unique hash for each layer, so
 Images are basically versioned (think git)
 can be tagged ubuntu:14.04.1
 can be updated by applying layer deltas
 Images can be stored in an Index
 local and remote indexes (think maven / npm repos)

12. So a container is like a
lighter/better Virtual Machine?
Well...

13. VM vs Container
 A Virtual Machine
 needs an hypervisor
 and a full OS inside
 Bigger footprint
 RAM needed
 Storage space
 Tend to be slower
 2 filesystems, 2 OSes
 Strong resource
management
 A Container
 talks to the host kernel
 Smaller footprint
 no RAM needed for
Guest OS
 differential storage
 Tend to be faster
 direct CPU access
 Less sophisticated
resource management

14. VM vs Container

15. Great! but tell me about security
 Are containers less secure than Vms?
 the answer is nuanced...
 https://docs.docker.com/articles/security/
 Can I use Docker in Production?
 Sure! many Internet companies trust it
 But a container still needs good System
Administration & InfoSec practices!
 limiting privileges, avoiding unsecure defaults, etc...
 http://www.slideshare.net/jpetazzo/docker­linux­conta
iners­lxc­and­security
 http://opensource.com/business/14/7/docker­security­s
elinux
Avoid This!

16. Docker workflow

17. Start with a dockerfile
 Define an image for running Tomcat 7
 inspired by https://registry.hub.docker.com/_/tomcat/
FROM java:7­jre
RUN groupadd ­r
tomcat && useradd ­r
­­create­home
­g
tomcat tomcat
ENV CATALINA_HOME /usr/local/tomcat
ENV PATH $CATALINA_HOME/bin:$PATH
RUN mkdir ­p
"$CATALINA_HOME" && chown tomcat:tomcat
"$CATALINA_HOME"
WORKDIR $CATALINA_HOME
USER tomcat
ENV TOMCAT_MAJOR 7
ENV TOMCAT_VERSION 7.0.57

18. Dockerfiles - continued
ENV TOMCAT_TGZ_URL
https://www.apache.org/dist/tomcat/tomcat­$
TOMCAT_MAJ
OR/v$TOMCAT_VERSION/bin/apache­tomcat­$
TOMCAT_VERSION
.tar.gz
RUN curl ­SL
"$TOMCAT_TGZ_URL" ­o
tomcat.tar.gz
&& curl ­SL
"$TOMCAT_TGZ_URL.asc" ­o
tomcat.tar.gz.asc
&& tar ­xvf
tomcat.tar.gz ­­strip­components=
1
&& rm bin/*.bat
&& rm tomcat.tar.gz*
EXPOSE 8080
CMD ["catalina.sh", "run"]
 Public repo of Dockerfiles, with automatic build
 http://dockerfile.github.io/

19. Building an image
 Build the image from the Dockerfile
docker build .
 You can then do further edits, then
docker build .
 And archive the image locally
docker commit 38b73dfecc3c docker­simple­samples­web
 And tag it
docker tag 47432ccfea81 docker­simple­samples­web:
1.0
 List local images
docker images

20. Starting a container
 Start a container interactively
docker run ­i
­t
docker­simple­samples­web
/bin/bash
 Start a container as a daemon
 using defaul entrypoint
docker run ­d
docker­simple­samples­web:
1.0
 Check running containers
docker ps
 And stopping it
 docker stop <<id>>
 Check also stopped containers
docker ps ­a

21. Attaching to a running container
 Using nsenter
docker inspect ­­format
"{{ .State.Pid }}"
determined_bardeen
nsenter ­­target
$PID ­­mount
­­uts
­­ipc
­­net
­­pid

22. Storing and Sharing data
 Creating a Container to host a data Volume
#Dockerfile
FROM busybox
VOLUME /var/lib/mysql
CMD /bin/sh
 Create the Image
docker build ­­tag
carlobonamico/datastore
 Create the Container
docker run ­d
­name
pgsql_data ­v
/var/lib/pgsql/
carlobonamico/datastore
 Attach the volume to another container
docker run ­d
­volumes­from
pgsql_data cb/postgres­db

23. Publishing
 To the Central Registry
docker push carlobonamico/docker­simple­samples­web
 need a free account on
https://hub.docker.com/
 Tag and publish to a private repository
 docker tag 8dbd9e392a96 my­local­repo:
5000/docker­simple­samples­web
 You need
 https://github.com/docker/docker­registry

24. Deploy to the cloud
 On cloud server
docker pull carlobonamico/docker­simple­samples­web:
2
 Run it
docker run ­d
carlobonamico/docker­s...
­samples­web:
2
 Upgrade it
docker pull carlobonamico/docker­s...
­samples­web:
2.1
 Run it
docker run ­d
carlobonamico/docker­s...
­samples­web:
2.1
 Rollback to previous version
docker run ­d
carlobonamico/docker­s...
­samples­web:
2

25. So what do I get?
 If I am a Dev
 recreate complex environments on a laptop
 If I am a Tester
 easy to recreate applications deployments and data
 If I am an Ops person
 less configuration effort
 more standardization
 In general
 lots of pre-packaged components
 https://registry.hub.docker.com/
 quickly deploy (groups of) packages
 even multiple versions at the same time
But many
other benefits
to come...

26. Docker and DevOps
DevOps is a software development method that stresses
communication, collaboration and integration
between software developers and IT professionals,
as a response to the interdependence of Dev and Ops.

http://en.wikipedia.org/wiki/DevOps
 Docker gives a common, seamless collaboration
model and workflow between Dev and Ops
 clearer separation of responsibilities
 Docker and DevOps by Gene Kim
 https://www.youtube.com/watch?v=SaHbtEeu37M

27. Docker helps Continuous Delivery
Continuous Delivery of value to users through
a constant flow of incremental product/service
improvements along the entire pipeline
Idea → Implementation → Test → Deploy → Prod
http://continuousdelivery.com/
 4 Practices of Continuous Delivery (from the book)
 Build binaries only once
 package them in containers
 Same mechanism to deploy to every environment
 and move the containers across environments
 Smoke test your deployment, & If anything fails, stop
the line!

28. Docker helps with CD's 8 principles
 Releasing/deploying MUST be repeatable and reliable
 containers
 Automate everything!
 docker is fully scriptable and has an API
 If somethings difficult or painful, do it more often
 containers are quick to deploy many times a day
 Keep everything in source control
 including dockerfiles!
 Done means “released”
 it's containers all the way to production
 Build quality in!
 containers support frequent and realistic testing
 Everybody has responsibility for the release process
 see DevOps slide...
 Improve continuously

29. What do I put in a Docker image?
 The traditional Way
 VM-like approach
 SSH, init.d
 several apps in the same container
 http://phusion.github.io/baseimage-docker/
 https://registry.hub.docker.com/u/phusion/baseimage/
 Useful in the transition phase or to run existing SW
 The Docker Way
 run a service per container
 purists say a single process per container!

30. From a single container

31. To many containers
 Two key drivers
 Scalability
 Microservices

32. Microservices
Instead of big, monolitic, black-hole-like single app
implement a network of collaborating simple services
http://martinfowler.com/articles/microservices.html
“a bit like SOA, but done right”
 Componentization via Services
 Organized around Business Capabilities
 Products not Projects
 Smart endpoints and dumb pipes
 Decentralized Governance
 Decentralized Data Management
 Infrastructure Automation
 Design for failure
 Evolutionary Design
It looks like Docker
is a perfect match!

33. SOLID Design Principles
 Apply @unclebobmartin S.O.L.I.D. principles to
entire architecture
 Separation of Concerns → microservices
 Open for extension, Closed for modification →
Immutable Infrastructure
 never “change” a container: add a new one with the
new version then discard the old one
 http://blog.codeship.com/immutable­infrastructure/
 Liskov Substitution Principle → APIs, service contracts
 Interface Segregation Principle → micro-APIs
 Dependency Inversion Principle → container linking

34. Linking containers
 Run a DB
 and give it a name
docker run ­d
­­name
db postgres:9.3.5
 Run a Web server
docker rm ­f
carlobonamico/web
 does not see the db
 Run a Web Server linked to the DB
 with automatic local dns alias registration
docker run ­d
­P
­­link
db:db carlobonamico/d­s­s­web

35. Principles of Package Design
 How do I split functionality across Containers?
 REP The Release Reuse Equivalency Principle
 The granule of reuse is the granule of release
 CCP The Common Closure Principle
 Classes that change together are packaged together
 CRP The Common Reuse Principle
 Classes that are used together are packaged together
 ADP The Acyclic Dependencies Principle
 The dependency graph must have no cycles
 SDP The Stable Dependencies Principle
 Depend in the direction of stability
 SAP The Stable Abstractions Principle
 Abstractness increases with stability
 Thank you again, Uncle Bob
http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod

36. Managing Development and
Production clusters
 Fig http://www.fig.sh/
 create DEV environm.
 fig.yml
web:
build: .
command: catalina
.sh run
links:
­db
ports:
­"
8000:8000"
db:
image: postgres
 Then (think vagrant-up)
fig up

 open source
 https://github.com/g
ooglecloudplatform/k
ubernetes
 manage prod clusters
 use it on Google
Compute Engine
 or download on
premises

37. Ansible and Docker
 So I do not need a configuration management
system anymore?
 Well, you still need to
 Create images
 Manage the Docker host
 Ansible to the rescue!

38. Ansible
 Simple yet incredibly powerful Open Source
configuration management and orchestration tool
 Infrastructure as data
 http://www.slideshare.net/carlo.bonamico/infrastructu
re­as­data­with­ansible­for­easier­continuous­deliver
y
 Ansible can support Docker in two ways
 http://www.ansible.com/docker
 1) Manage the docker host with docker module
 e.g. create a container running Tomcat
docker: image=centos command="service tomcat6
start" ports=808

39. Building Images with Ansible
 2) Copy and launch ansible playbook in Dockerfile
 http://www.ansible.com/2014/02/12/installing­and­buil
ding­docker­with­ansible
 https://github.com/CaptTofu/ansible­docker­presentati
on
 Use base image with ansible from
https://registry.hub.docker.com/repos/ansible/
FROM ansible/ubuntu14.04­ansible
MAINTAINER yourname
RUN git clone http://github.com/user/myapp.git
/tmp/myapp
WORKDIR /tmp/myapp
ADD inventory /etc/ansible/hosts
RUN ansible­playbook
myapp.yml ­c
local
EXPOSE 22 3000
ENTRYPOINT [“/home/app/tomcat/bin/catalina.sh run”]

40. So, where do I start?
 Try the samples
 https://github.com/carlobonamico/docker­simple­sample
s
 Great interactive tutorial at
 https://docs.docker.com/
 https://docs.docker.com/articles/dockerfile_best­prac
tices/
 Try Docker in the Cloud
 with Koding ide
 http://learn.koding.com/guides/what­is­docker/

41. References
 Cloud architectures
 http://sites.oreilly.com/odewahn/dds­field­guide/
 http://12factor.net/
 Microservices
 https://skillsmatter.com/conferences/6312­mucon
 http://douglassquirrel.com/microservices/
 Distributions to put around and inside a container?
 https://coreos.com/
 Docker and Windows
 http://weblogs.asp.net/scottgu/docker­and­microsoft­i
ntegrating­docker­with­windows­server­and­microsoft­a
zure

42. Thank you!
 Other presentations
 http://www.slideshare.net/carlo.bonamico/presentations
 Follow me on Twitter
 @carlobonamico
 updates on Docker, Ansible, Continuous Delivery
 and some AngularJS!
 Contact me
 carlo.bonamico@gmail.com / carlo.bonamico@nispro.it
 My company
 http://www.nispro.it

43. Running on Mac/Windows
 Boot2docker
 A minimalistic VM – just SSH + docker
 http://boot2docker.io/
 Download and launch the installer
 https://github.com/boot2docker/windows­installer/
rele
ases/latest
 Launch docker
Boot2Docker Start