all things open 2015: docker: everything you should know
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Docker: Everything you
should know
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Who am I?Aaron Huslage (@huslage)
Sysadmin since 1993
Since April 2014: Solution Engineer @ Docker
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OutlineWhy Docker?
What's Docker?
How to get started?
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Why Docker?
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Why Docker?Faster application development cycle
Multiplication of environments
Scaling requirements
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Yesterday: slow cycles (months/years)Specification
Implementation
Validation
Release
Maintenance
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Today: fast cycles (weeks/days)Minimum Viable Product
Short iterations (sprints)
Continuous Deployment
A project is never "done" or "over"
Agile methods
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Yesterday: single environmentOne language
One framework
One database
One server (+ sometimes a dev environment)
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Today: many environmentsMany languages
Polyglot platforms
Simultaneous use of SQL, NoSQL ...
The right tool for the right job
Many servers (everybody has their local dev env; there are many envs for testing, CI, QA, etc.)
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Yesterday: slow, vertical deploymentNew versions once in a while
Installed to few servers (sometimes just one)
Scaling = scaling up (you're gonna need a bigger server)
Scaling must be planned far ahead
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Today: rapid, horizontal deploymentNew versions all the time (every week / day / hour)
Installed to many servers
Scaling = scaling out (MOAR servers!)
Need to be able to scale quickly
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What is Docker?
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What is Docker?Container execution engine
Container build system
Container image distribution
Ginormous ecosystem
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Container execution engine~Hypervisor for containers
Container =~ lightweight virtual machine
... What is a container???
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ContainerIt looks and feels like a VM
Standard UNIX processes, isolated by kernel mechanisms:
namespaces
cgroups (control groups)
copy-on-write
Insanely fast boot times
Insanely low resource usage
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Build systemDockerfile = recipe describing the build process
Easy to learn (similar to shell scripting)
Fast (caching system)
Reliable, reproducible
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Build systemDockerfile = recipe describing the build process
Easy to learn (similar to shell scripting)
Fast (caching system)
Reliable, reproducible
Let's have our cake - and eat it too
(Compared to classic scripting, or configuration management systems like Puppet, Chef, Salt, Ansible...)
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Image formatProblem: VM images are big
Solution 1: container images are smaller
doesn't need hardware support, kernel, drivers ...
separate handling of logs, metrics, backups ...
Solution 2: images broken down into layers
1 layer = 1 build step
example: base system, packages, code, config
only transfer updated layers
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Distribution protocolProblem: it's both too simple and too complicated
"just do tar or rsync ...
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Distribution protocolProblem: it's both too simple and too complicated
"just do tar or rsync ...
... with these 5 cryptic options, and it works"
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Distribution protocolProblem: it's both too simple and too complicated
"just do tar or rsync ...
... with these 5 cryptic options, and it works"
(mostly)
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Distribution protocolProblem: it's both too simple and too complicated
"just do tar or rsync ...
... with these 5 cryptic options, and it works"
(mostly)
Solution: Docker Registry
transfer layers via an open REST API
open source reference implementation
free service for public images (à la GitHub)
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Ecosystem: images~100 official images
Linux distros (Debian, Ubuntu, CentOS, Fedora, ...)
components (MySQL, Redis, PostgreSQL, MongoDB, NGINX...)
languages (Python, Ruby, Java, Go, Node...)
applications (Wordpress...)
~150,000 contributed images
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Ecosystem: code~100,000 GitHub repositories have a Dockerfile
~1000 contributors to Docker code
Thousands of projects integrating with Docker
Some official tools:
Machine (deploy Docker hosts)Compose (manage multi-container applications)Swarm (cluster multiple Docker hosts together)
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One example: Docker ComposeAssemble application from multiple containers
Define parameters of each container
how to build it
how to run it (command, arguments, environment...)
network port mappings
linking between containers
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How to getstarted?
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If you're in a hurryOS X, Windows: Docker Toolbox + boot2docker
tiny VM image (less than 30 MB)
works on (most) physical and virtual machines
Linux: get.docker.com
shell script
usable with Cloud Init or |sh*
* Make sure you use https and nobody gets hurt!
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If you like readingdocs.docker.com
start with "get started" (duh!) (it's written in good old "howto" style)
reference documentations
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If you like looking at / listening totraining.docker.com
Free, official training videos
Intro to Docker (general concepts)
Docker Fundamentals (first steps with Docker)
Docker Operations (using Machine, Swarm, Compose)
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How to "Dockerize" my app?1. Write a Dockerfile for the main component
2. Write a docker-compose.yml for the app itself
3. Use Docker+Compose during development
4. Use Docker+Compose for testing/QA/acceptance...
5. (Optionally) setup CI/CD
6. Go to production with Docker+Compose (static resource scheduling)
If you have 100s of apps with 100s of containers (each): setup a self-service container platform for your developers (using e.g. Swarm, Mesos, Kubernetes...)
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