Docker vs Vagrant
Sep 11, 14 by Juan Lebrijo about docker, scalability, vagrant, blog
Thanks to a question of my friend Xavier: "Is this something that might potentially interest us? CoreOS Now Available On DigitalOcean!", I reopened this internal discussion "Vagrant or Docker, this is the question?". Well here are my thoughts .... CoreOS is a minimal Linux Distro in order to save RAM when you manage Clusters (or slices within a machine). They promise  to use only 144MB RAM. When you use Docker, you need a host OS in your Server (CoreOS promises to be the lighter host OS). So the question here is ...... should we use Docker?
  • SERVER SIDE:
    • Docker/CoreOS are scalability tools: as Adrian said this is a really powerful tool to scale applications, you can deploy packaged containers (slices) within a server and among servers in a farm. CoreOS seems to help a lot at this point also, running 'etcd' by default.
    • Removes Lock-in: You can move your apps among providers (DO, Rackspace, AWS, Linode,... your private farm). Once you have your container configured, you just need to have a linux host (an AWS linux AMI, Ubuntu, CoreOS ....) with Docker installed.
  • DEVELOPER SIDE: Docker instead of Vagrant to emulate the system locally (take a look at this great discussion between both creators)
    • This is only possible, for the moment, if your app servers are linux (this does not mean that your Dev workstation should be Linux)
    • Docker engine (Virtualization layer) is based on LXC, which manages chroot, network, mount... all kernel "Containerizing" capabilities directly. This efficiency is extreme if your local OS is Linux.
      • Vagrant lies over VirtualBox which creates a lot of CPU and Memo overhead.
    • Portability: Docker allows to reproduce EXACTLY the production scenario in your workstation (or other environments like staging or testing). You just need Docker/Linux installed in both, and Docker acts as an abstraction layer.
      • Vagrant offers images which haven't the same configuration as your provider's images (I experienced this directly: ubuntu-14.04 has not the same configuration in vagrantcloud.com's box, and DigitalOcean.com's image)
    • Images weight: Vagrant boxes are much larger than Docker repos (ubuntu/trusty is ~600MB image box, against 64MB as Docker repo)
I was until this weekend with an eye on this Infrastructure Maintenance Stack:
  • Chef: Manages server installation and future configurations.
  • Vagrant: reproduces (approximately) our production server in order to check configurations.
  • Capistrano: Manages continuous deployment.
But due to read (and tests) about Docker this weekend, I am thinking to substitute Vagrant per Docker (the reasons above are really persuasive). So, hey guys!! what do you think? Is Docker/CoreOs something that might potentially interest us?