Introducing and playing with Docker

Manel Martinez Gonzalez@manel_martinezg

About me

● I am a Catalan (from Barcelona)

● +10 years of experience as a Systems Engineer

● I focus my career on helping companies with:

○ Stabilizing Production environments○ Building Agile-friendly development environments (Continuous Integration and

Continuous Delivery)○ Automating everything

● Discovered Docker at 2014

○ Since then, my working tool

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About Docker

● A recent product that makes it easy to work with Linux Containers

● Mainly composed by:

○ The Docker daemon, which controls containers○ The Docker images, where we pack (build) our services○ The Docker containers, where we run our services○ The Docker CLI, which help us interact with Docker daemon

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About Docker

● Main Docker features:

○ Dockerfile => image descriptor○ Docker Hub => public & private image repositories○ Linking => interconnecting containers○ Labeling => container/image metadata○ Volumes => persist & share containers data ○ Docker Machine => automated server provisioning○ Docker Compose => automated multi-container app deploying○ Docker Swarm => clustering solution

● Install last daemon & CLI version (debian & redhat like distros):

wget -qO- https://get.docker.com/ | sh

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Using Docker

● Useful docker commands

docker run => Create a new containerdocker stop => Stop a running containerdocker start => Start an existing containerdocker restart => Restart an existing containerdocker ps => List existing containersdocker inspect => Get low-level container/image informationdocker rm => Delete an existing containerdocker exec => Run a command in a running container

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Using Docker

● Using existing images - the ‘Hello world’ container

docker run ubuntu:14.04 /bin/echo 'Hello world'

● Dockerizing an application (creating an image)

○ Write the Dockerfile and add required image sources○ Build the image docker build -t

repo/image-name:tag .○ Push the image docker push repo/image-

name:tag○ Run the containers docker run [options] repo/image-

name:tag

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Dockerfile

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● Environment variables

● Volumes

● Ports

● Commands

● And more

Docker Hub

● Public & private Docker image repositories

● Docker images are based on a Dockerfile and source files

● Dockerfile is used to describe the image

● Once the image is built we push it to aDocker Hub repository

● Then it is ready to be deployed onany environment

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Docker Hub

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Linking

● Linking is useful to interconnect containers

docker run [options] --link some-mysql:mysql ...

● Link name resolves the linked container IP (added on /etc/hosts file)

172.10.0.7 mysql

● Environment variables and ports on linked container are exposed as new environment variables

MYSQL_ENV_MYSQL_ROOT_PASSWORD=abc123MYSQL_PORT_3306_TCP_PORT=3307

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Labeling

● Labeling is useful to set metadata on containers / images

docker run [options] --label key=”value” ...

● Used to extend Docker functionalities

○ Setting variables that won’t be exposed when linking○ Setting custom information○ Identifying / grouping containers

docker ps --filter “label=key=’value’”

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Volumes

● Containers are volatile, all their data is deleted when you delete the container

● Volumes help us to persist data

docker run [options] --volume=/path/on/server:/path/on/container ...

● Or to share data across containers

docker run [options] --volumes-from [some container] ...

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Docker Machine

● Binary used to provision remote Docker hosts and set up communication with your local Docker CLI

curl -L https://github.com/docker/machine/releases/download/v0.4.0/docker-machine_linux-amd64 > /usr/local/bin/docker-machinechmod +x /usr/local/bin/docker-machine

● Can manage multiple servers on different cloud providers (or your own infrastructure): Amazon EC2, DigitalOcean, Azure, Google Compute Engine, etc

docker-machine create -d digital-ocean --digitalocean-access-token=XXXX server1

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Docker Compose

● Binary used to manage multiple containers and volumes

curl -L https://github.com/docker/compose/releases/download/1.4.1/docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-composechmod +x /usr/local/bin/docker-compose

● Based on a compose YAML definition file

$ docker-compose up -dCreating test_db_1…Creating test_wordpress_1…

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wordpress: image: wordpress links: - db:mysql ports: - 8080:80db: image: mariadb environment: MYSQL_ROOT_PASSWORD: example

Docker Swarm

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Docker Swarm

● Docker client (swarm manager) that sends requests to appropriate Docker daemons (swarm agent) running in a cluster

● Useful to manage all Docker hosts and containers from a single Docker CLI

● Used with Machine and Compose to automatically provision hosts and containers

● Create a swarm manager using Machine:

docker-machine create -d digital-ocean --swarm --swarm-master --swarm-discovery token://d78a10ca90563d464e19e2246404d22b swarm-master

● Create a swarm agent using Machine:

docker-machine create -d digital-ocean --swarm --swarm-discovery token://d78a10ca90563d464e19e2246404d22b swarm-agent-00

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Docker Swarm

Scheduling rules used to decide in which hosts to deploy containers based on filters. For example:

● Constraint filter: deploy containers on hosts that meet a condition

docker run [options] -e constraint:storage==disk …

● Container affinity filter: deploy containers next to other containers

docker run -d -p 80:80 --name frontend nginxdocker run -d -e affinity:container==frontend

logger

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Docker Swarm

● Label affinity filter: deploy containers next to other containers using labels

docker run -d -p 80:80 --label com.example.type=frontend nginx

docker run -d -e affinity:com.example.type==frontend logger

● Port filter: deploy containers on hosts where exposed ports are available

docker run -d -p 80:80 nginx => deployed on host1docker run -d -p 80:80 nginx => deployed on host2docker run -d -p 80:80 nginx => deployed on host3

● Dependency filter: deploy inter-dependent containers together (links, volumes)

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Docker Swarm

● Strategies for ranking nodes based on available CPU and RAM

● When nodes have the same ranking, these strategies can be set:

○ Spread: deploy containers on nodes that have the fewest containers

■ Best container distribution - if a node fails, less resources are impacted

○ Binpack: deploy containers on nodes that have more containers

■ Less fragmentation - fewer nodes are required

○ Random: choose a node randomly

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Demo time

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