Docker for Development

Quick introduction to Docker and how it fits the modern development workflow, plus a few tips about running docker inside Vagrant and on the differences between docker run and docker exec.

I originally gave this talk internally at HelloFresh in March 2016, and later at the August meetup of Berlin PHP Usergroup.

Transcript

1. Docker for Development Pedro Gil @pgcandeias Container Docks, 2/12 © 2012 Louis Vest - https://flic.kr/p/bSrWHc
2. About me • Mostly into dynamic languages (php/js/python) • Head of Platform Engineering at HelloFresh • Migrating monoliths into microservices • Taking care of the services and tools used by our developers
3. What’s Docker? “Docker 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.” https://www.docker.com/what-docker
4. Containers • Similar to virtual machines • Don’t need a whole OS per container • Much smaller than VMs https://www.docker.com/what-docker
5. VM vs container architecture https://www.docker.com/what-docker
6. Container benefits • Consume very little memory and disk • We can run lots and lots of them in a laptop • Spin up in under a second • Disposable Container © 2013 www.GlynLowe.com - https://flic.kr/p/hD7Jqz
7. So basically… We can run very complex distributed systems with dozens of hosts We can closely simulate production topology In our laptops! © 2015 Dirk Dallas - https://flic.kr/p/qZbDqf
8. What’s Docker? Docker is witchcraft. La Bruja del Mar © 2012 Sergio Otero - https://flic.kr/p/eFAV7T
9. That’s nice, kid but what’s in it for me? © Lucasfilm Ltd - http://www.starwars.com/databank/han-solo
10. First, a little perspective Let’s take a look at where we came from
11. In the olden days… • We worked on bare metal • Language interpreters, databases and web servers all installed in our machines • Working with multiple versions of the same thing (language, database, etc) sucked • Environment management solutions emerged • Many differences between development and production. Ibiza Medieval 2011 © 2011 Juan Pacheco Tirado - https://flic.kr/p/9Fnrnp
12. Enter Vagrant • Easy virtualization • Same environment in development and production • Different VMs for different projects, each with its own dependency versions • Easy to share https://commons.wikimedia.org/wiki/File:Vagrant.png
13. Vagrant issues • Still a lot of overhead • No easy way to accurately represent large, diverse topologies • Untenable for large, distributed applications https://www.docker.com/what-docker
14. Container benefits • Consume very little memory and disk • We can run lots and lots of them in a laptop • Spin up in under a second • Disposable https://www.docker.com/what-docker
15. Docker architecture
16. Docker requires Linux Other OSes, such as OS X or Windows, require using some sort of linux based virtual machine for Docker Engine to run. Docker machine (previously boot2docker) is basically just a linux VM with docker engine inside.
17. Use docker machine. Problem? • Broken filesystem sync • Live code editing doesn’t work • No big deal for compiled languages, but it sucks for php, JS, python, etc • Accessing each app on a different port also sucks • So yes, Sherlock, problem. http://www.independent.co.uk/
18. Vagrant to the rescue • Proper NFS shares allow code changes to propagate to containers • Multiple network interfaces allow multiple apps to run on port 80 (for example) • Really nice customisation all around • Still easy to share https://commons.wikimedia.org/wiki/File:Vagrant.png
19. docker compose creating a nice application cluster with your code and all ancillary services like databases
20. docker run vs docker exec
21. docker run -ti ubuntu bin/bash • Pulls the ubuntu image from a registry • 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 (hello) • Captures and provides application output • Stops the container as soon as the command is done
22. docker exec -ti ubuntu_1 bin/bash • Executes a comand in an already running container • In this case, executing bash means you get a shell • This is how you can see logs for an application server, for instance • Any changes made during this session persist in the running instance
23. In summary • Docker allows developing on a topology that resembles production much more closely than bare metal or VMs • Doesn’t run on OS X but we can fix that using a vagrant box with docker-engine installed • docker-compose lets us define complex clusters easily for development • Containers are cheap. Kill them, restart them, change their versions easily.
24. Thank you! Pedro Gil @pgcandeias pgscandeias@gmail.com github.com/pgscandeias Container Docks, 2/12 © 2012 Louis Vest - https://flic.kr/p/bSrWHc