Containers

Containers wrap up a piece of software in a complete filesystem that contains everything it needs to run: code, runtime, system tools, system libraries – anything you can install on a server.

This guarantees that it will always run the same, regardless of the environment it is running in.

Containers vs. VMs

Docker Architecture

Images & containers

Images

Are read-only templates

Composed by layers using Union File System

Parent image + new layers

Containers

User added files

Metadata

UnionFS + namespaces + cgroups

Image + new read-write layer

Let's run a container

Pulls the ubuntu image from docker hub

Creates a new container

Allocates a filesystem and mounts a read-write layer

Allocates a network / bridge interface

Sets up an IP address

Executes a process that you specify

Captures and provides application output

docker run -i -t ubuntu /bin/bash

see docker hub

Dockerfile

https://github.com/docker-library/postgres

FROM

ENV

ADD

COPY

WORKDIR

RUN

EXPOSE

VOLUME

USER

CMD

ONBUILD

example

Multiple containers?

Docker compose

A tool to compose and run multiple isolated environments on a single host using docker containers

• Development environments
• Automated testing environments
• Not recommended for production yet

Hands on

https://git.sophilabs.io/ssassi/test-docker-django/tree/master

nginx

django

redis

postgres

data

web:
  restart: always
  build: ./web
  expose:
    - "8000"
  links:
    - postgres:postgres
    - redis:redis
  volumes:
    - /usr/src/app/static
  env_file: .env
  command: /usr/local/bin/gunicorn docker_django.wsgi:application -w 2 -b :8000

nginx:
  restart: always
  build: ./nginx/
  ports:
    - "80:80"
  volumes:
    - /www/static
  volumes_from:
    - web
  links:
    - web:web

postgres:
  restart: always
  image: postgres:latest
  volumes_from:
    - data
  ports:
    - "5432:5432"

redis:
  restart: always
  image: redis:latest
  ports:
    - "6379:6379"

data:
  restart: always
  image: postgres:latest
  volumes:
    - /var/lib/postgresql

Docker Machine

Manage local and remote docker hosts

• Needed on Windows and OSX machines
• Supports most VM Systems and Cloud Hosting Providers
  • VirtualBox, VMWare, Softlayer, Hyper-V
  • AWS, Azure, DigitalOcean, Rackspace, Google, Exoscale

docker-machine create -d virtualbox dev;

eval "$(docker-machine env dev)"

docker-machine ls

New docker machine

docker-compose build
docker-compose up -d

docker-compose run web /usr/local/bin/python manage.py migrate

git clone git@git.sophilabs.io:ssassi/test-docker-django.git

Clone repo, build it and run it!

docker ps -a

Kitematic

a GUI for lazies

Scalability & Availability

Cluster Managers

cluster managers war

flynn

deis

coreos

mesos

maestro

openstack

panamax

clusterhq

atomic

kubernetes

decking

shipyard

lattice

rancher

helios

swarm

tutum

http://stackoverflow.com/questions/18285212/how-to-scale-docker-containers-in-production

Docker Swarm

Official clustering solution for docker, including scheduling, scalability and availability management

• Is under development
• Master-slave design
• Multiple discovery backends
  • static file
  • etcd
  • consul
  • zookeeper
• Multiple scheduling strategies and rules
• Hosts can be created on any cloud hosting provider

Swarm Strategies

Strategies for containers allocation on available hosts

• random
  • chooses a random host
• spread
  • prefers the hosts with less containers running
• binpack
  • prefers the hosts with most containers running

Swarm Scheduling

Available filters for containers allocation on available hosts

• constraint
  • assign tags to hosts and then filter by them
• affinity
  • require that container runs next to another one
• port
  • requires that a specific port is available
• dependency
  • collocates dependent containers by resources sharing
• health
  • avoid unhealthy nodes

docker-machine create -d virtualbox --swarm --swarm-master --swarm-discovery token://08c73c596622ad6010d22ad4ec043ca7 swarm-master

Let's create a cluster

master

slave nodes

docker-machine create -d virtualbox --swarm --swarm-discovery token://08c73c596622ad6010d22ad4ec043ca7 swarm-agent-00

docker-machine create -d virtualbox --swarm --swarm-discovery token://08c73c596622ad6010d22ad4ec043ca7 swarm-agent-01

eval $(docker-machine env --swarm swarm-master)

...adding a new container

get info

slave nodes

docker run hello-world

docker info

docker ps -a

Docker containers

Dockerfile

Docker hub

Kitematic

Docker compose

Docker machine

Docker swarm

Summary

Thanks