Another introduction to DockerTibor Vass

Who Am I?

• Core maintainer on Docker Engine

• Previously Ops @ StumbleUpon

• I ♡ Go

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Tibor Vass, Chapel Hill, NC

IRC #docker: tibor Twitter: @tiborvass

Outline• Challenges • What’s needed • What is Docker • Getting started • Docker concepts

– Engine – Images & Containers – Builds – Compose

• Deployment Workflow3

Challenges

1. Deployment & Guarantees

1. Separation of concerns (Dev vs Ops)

Code deployment…

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CI fetches codebuilds it and runs tests

If ok, allow deployment of code

push code to git server

Prod

Deploy code

hookkicks CI

… in different environments!

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Newest version of PythonCode assumes port 1234 available

Older version of Python Port 1234 takenMissing dependency

… in different environments!

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Newest version of PythonCode assumes port 1234 available

Older version of Python Port 1234 takenMissing dependency

AngryUsers

… in different environments!

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Newest version of PythonCode assumes port 1234 available

Older version of Python Port 1234 takenMissing dependency

AngryUsers

“Works for me!”

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Code deployment

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Code deployment

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Code deploymentNeed “Code + environment” deployment

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Code deploymentNeed “Code + environment” deployment

Need a portable unit of deployment (guaranteed to work everywhere)

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Virtual Machines?

2. Density & Resource usage

Density & Resource usage• One app per server

– waste of idle resources – huge costs

• One app per VM, multiple VMs per server – Better resource pooling – Easier to scale – Pay as you go (cloud) – Not *that* portable – Requires resource allocation

(cpu, RAM, disk, …) – GuestOS duplicated – Resource hungry

17 Hardware

Host OS

Hypervisor

GuestOS GuestOS

AppApp

Hardware

Host OS

App

3. Move fast, and don’t break things

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Make your product better faster (stronger♫) to gain competitive advantage

What’s needed

What’s needed• Something like VMs… • Isolates processes from storage, networking, memory, cpu (sandboxing)

• …but lighter • Lightweight portable unit of deployment (packaging & distribution)

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Docker container/image

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Hardware

Host OS

App App App

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Hardware

Host OS

Hardware

Host OS

Hypervisor

GuestOS GuestOS

codebins/libs

codebins/libs

code code codebins/libsshared bins/libs

As many shared layers as possible

VM Container

VM vs Container

What is Docker?

Challenge #0: Satisfying Users’ expectation of reliability and availability

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Dream: what if, you could build distributed appseasily, and focus on your product?

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Distributed and scalable services gotta be independent from the machines they run on

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Containers are part of the answer

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Docker’s greatest value does not liein its technology

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It lies in its ability to get peopleagree on something

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Open platform inviting you to help make the dream happen

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Or simply enjoy and contribute to each independent piece along the way

Docker• Engine • Hub • Distribution (Private registry) • Machine • Compose • Swarm • Kitematic • More to come…

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Getting Started

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Install Docker: https://docs.docker.com/installation/

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(install Machine and Compose as well)

Docker concepts

1. Engine

Engine• Docker Daemon + REST(ish) API • Docker Client (CLI) talks to the API

• Daemon manages the Docker containers • Start it with: docker -d

• docker version to test if docker is set up correctly

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2. Images & Containers

Images vs Containers• Images: About storing or moving your app

• Containers: About running your app

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Image• Read-only snapshots (templates) for creating containers • Stored on the Docker Hub or on a private registry (or in a tar archive) • Cannot be run, has to be instantiated into a container • Look around on Docker Hub for existing images

• List images:docker images

• Download busybox:docker pull busybox

• Remove busybox image:docker rmi busybox

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Containers• Sandboxed application

• docker ps• docker create —name hello busybox echo hello posscon• docker start -a hello• docker start -a hello # same container started again • docker rm hello• docker run busybox echo hello posscon

• WARNING: run = create + start, so each “run” spawns a new container (ephemeral)

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Containers• Launch an interactive shell:

docker run -i -t busybox sh • Expose ports of an image:

docker run -P training/webapp python app.py • Read host port on docker ps • Detached mode:

docker run -d -P training/webapp python app.py • Expose to specific host ports:

docker run -d -p 1234:5000 training/webapp python app.py

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3. Builds aka Dockerizing

Build images• Example layout of a Dockerfile placed alongside with the code

• FROM ubuntu:14.04• RUN apt-get update && apt-get install -y golang• ENV GOPATH=/go• COPY . /go/src/myapp• EXPOSE 8080• RUN go build myapp• CMD [“/go/bin/myapp”]

• Build new image named myapp: docker build -t myapp . • Change code, and rerun the build command: notice that Docker cached the dependencies and

won’t fetch them again by default (use —no-cache if desired)

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Build with official images• No need to use FROM ubuntu and install common dependencies anymore! • Use official golang image: • FROM golang• COPY . /go/src/myapp• …

• Even simpler: • FROM golang:onbuild• # something will listen on port 8080• EXPOSE 808048

4. Compose

Compose your stack of containers• In a docker-compose.yml: • wordpress:• image: wordpress• links:• - db:mysql• ports:• - 8080:80• db:• image: mariadb• environment:• MYSQL_ROOT_PASSWORD: example

• docker-compose up• http://<IP>:8080 where IP is the IP of the Docker daemon

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Deployment Workflow

App deployment…

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CI fetches codebuilds an IMAGE on which it runs tests

push code to git server hookkicks CI

Prod

Docker Hub orprivate registry

If ok, pushIMAGE toregistry

Deploy IMAGE

… in different environments!

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Dockerfile described the Dockerimage with its dependencies and Dev tested his code in that Docker image

Same Dockerfile Same Docker image

Docker image safelystored and tagged

Learn more

Learn more• https://docs.docker.com/

• swarm • security • machine • volumes • exec • logging • monitoring

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THANK YOU