Docker in practice at Selinko Discover why and how we use Docker, and what we learned about it.

1. DOCKER IN
PRACTICE
SELINKO

2. SELINKO
Belgian company based in LLN, with offices in
Taiwan & Washington DC
September 2012
Patrick Eischen • CEO
Didier Delhez • CTO
Gwen Festraets • VP Marketing & Communications
Jean-Pierre Pirson • VP Sales
14
SELINKO S.A.
LAUNCH
FOUNDERS
EMPLOYEES
PARTNERS Inside Secure (International leader in contactless technology)
Zetes (European leader in Track & Trace)
MICROCHIPS TRACK & TRACE

3. SECURE IOT PLATFORM
Connected
objects
Unique
Digital
Identity

4. OUR CONSTRAINTS
•International brands
•Mobile App
•User Experience has to be fast
•Great Firewall

5. WHY DO WE USE DOCKER?
• 12 factors (12factor.net)
• Setup automation
• Portability
• Reproducibility
• Scalability
• Security
• Multiple regions
• Microservices

6. HOW DO WE USE DOCKER?
• Development:
• Docker Machine
• Docker Compose

7. MQCore DB
Core App
Short DB
Core
Worker
Short App
SMTP
Core Web Short Web

10. HOW DO WE USE DOCKER?
• Development:
• Docker Machine
• Docker Compose
• Test:
• Jenkins
• Production:
• CoreOS
• systemd

11. [Unit]
Description=Postgres
After=docker.service
Requires=docker.service
[Service]
TimeoutStartSec=0
ExecStartPre=−/usr/bin/docker kill postgres
ExecStartPre=−/usr/bin/docker rm postgres
ExecStart=/usr/bin/docker run −−name postgres
−−volumes−from postgres_data postgres:9.4
ExecStop=/usr/bin/docker stop postgres
[Install]
WantedBy=multi−user.target

12. [Unit]
Description=Selinko Platform Core Webserver
After=core_app.service
BindsTo=core_app.service
[Service]
TimeoutStartSec=0
ExecStartPre=-/usr/bin/docker kill core_web
ExecStartPre=-/usr/bin/docker rm core_web
ExecStart=/usr/bin/docker run --name core_web
--volumes-from core_app:ro --link core_app:app
registry.selinko.com/selinko/nginx-rails
ExecStop=/usr/bin/docker stop core_web
[Install]
WantedBy=multi-user.target

13. WHAT WE LEARNED
• Not a lightweight VM
• One process per container
• Data volumes
• Don’t run as root

14. WHAT WE LEARNED
• Watch out for layers

15. FROM registry.selinko.com/selinko/ruby
COPY Gemfile Gemfile.lock /app/
RUN sudo apt-get update
RUN sudo DEBIAN_FRONTEND=noninteractive apt-
get install -yq --no-install-recommends build-
essential libpq-dev ruby-dev zlib1g-dev
RUN bundle install --retry 200
RUN sudo apt-get autoremove -yq --purge build-
essential libpq-dev ruby-dev zlib1g-dev xz-
utils
COPY . /app

16. FROM registry.selinko.com/selinko/ruby
COPY Gemfile Gemfile.lock /app/
RUN sudo apt-get update &&
sudo DEBIAN_FRONTEND=noninteractive apt-
get install -yq --no-install-recommends build-
essential libpq-dev ruby-dev zlib1g-dev &&
sudo rm -rf /var/lib/apt/lists/* &&
bundle install --retry 200 &&
sudo apt-get autoremove -yq --purge build-
essential libpq-dev ruby-dev zlib1g-dev xz-
utils
COPY . /app

17. WHAT WE LEARNED
• Watch out for layers
• Image size is virtual

18. REPOSITORY VIRTUAL SIZE
debian 125.1 MB
registry.selinko.com/selinko/ruby 163.8 MB
registry.selinko.com/selinko/uwsgi-ruby 172.3 MB
selinko/short-url-dispatcher 224.2 MB
selinko/platform 581.2 MB
SUM 1266.6 MB ???

19. REPOSITORY VIRTUAL SIZE
debian 125.1 MB
registry.selinko.com/selinko/ruby 163.8 MB
registry.selinko.com/selinko/uwsgi-ruby 172.3 MB
selinko/short-url-dispatcher 224.2 MB
selinko/platform 581.2 MB
SUM 633.1 MB o/
Debian
Ruby
uWSGI
Short
Debian
Ruby
uWSGI
Platform

20. WHAT WE LEARNED
• Watch out for layers
• Image size is virtual
• No init:
• Signals
• Zombies
• When needed, use Tini (github.com/krallin/
tini)

21. WHAT WE LEARNED
• Dev convenience:
• Docker Compose wrapper
• IDE debugging
• Official images
• Entrypoints

22. WHAT WE LEARNED
• Links can break easily:
• Docker Compose: recreate
• systemd: BindsTo
• Alternative: SkyDNS

23. • Cost to use Docker properly:
• learning curve for ops
• learning curve for dev
• Evolves really fast
WHAT WE LEARNED
Everybody becomes DevOps!

24. THANK YOU!