Introduction to Docker

Introduction to Docker

• 1.
  Docker AKA “the lastVagrantfile you’ll ever need”* * Disclaimer: probably not the last Vagrantfile you’ll ever need
• 2.
  What is Docker? http://docker.io/  “Docker is an open-source project to easily create lightweight, portable, self-sufficient containers from any application.”  Based on LXC (linux containers)  From dotCloud  Written in Go
• 3.
  …but what isit really?  Dockerfile to define a starting point (eg. “Centos”) and a set of instructions to prepare your environment and run your application  Image(s) containing all the defined environment and your app  Containers with running processes  All self contained and isolated from the host  Public registry of other people’s images
• 4.
  Why would Iuse it?  Dev/prod/staging consistency  Ability to streamline CI/CD
• 5.
  Performance  Each containeris simply a process, no other overheads (simply isolated in the kernel).  Run 10-100 containers on your laptop, each one self- contained  CPU == native, Memory == slightly higher, Network == _slightly_ slower  Copy on write filesystem (AUFS or BTRFS)
• 6.
  Structure  Encourages micro-servicesapproach  Every separate daemon should be it’s own container  Discourages talking to localhost or making naive assumptions about all services being locally accessible  Has a “linking” system for exposing other container IP and port details via environment variables  Also encourages viewing services (containers) as immutable
• 7.
   Docker encouragesa full CI/CD pipeline
• 8.
  Installation  Trivial onmodern linux (apt-get or yum install lxc- docker)  Near-trivial on OS X (install boot2docker, or dvm)  Latest AWS images now support docker by default (as does EBS)  Various vagrant images available for vbox, vmware, etc
• 9.
  Example Dockerfile FROM centos MAINTAINERKevin Littlejohn <kevin@littlejohn.id.au> RUN echo 'NETWORKING=yes' > /etc/sysconfig/network # Install Postgresql RUN rpm -i http://yum.postgresql.org/9.3/redhat/rhel-6-x86_64/pgdg-redhat93-9.3-1.noarch.rpm RUN yum install -y postgresql93-devel postgresql93 postgresql93-server postgresql93-contrib ENV PATH /usr/pgsql-9.3/bin:$PATH RUN service postgresql-9.3 initdb en_AU.UTF-8 ADD pg_hba.conf /var/lib/pgsql/9.3/data/pg_hba.conf RUN service postgresql-9.3 start && chkconfig postgresql-9.3 on && su postgres -c "createuser –s postgres" USER postgres EXPOSE 5432 CMD ["/usr/pgsql-9.3/bin/postgres", "-D", "/var/lib/pgsql/9.3/data", "-i", "-h", "0.0.0.0"]
• 10.
  12 Months ofDocker  Contributions from more than 400 developers;  More than 1.4 million downloads;  More than 10,000 Dockerized applications available in Docker’s public index; and  Accelerating community engagement, including more than 77 Docker Meetup groups in 30 countries.
• 11.
  Add-ons  Drone  Shipyard Registry  CoreOS  Fig  Maestro  Continuously !
• 12.
  Integrations  Packer  Vagrant Jenkins (Docker build step and Docker plugin)  Docker (DinD)  Google AppEngine  OpenStack
• 13.
  Systems Using Docker Travis-CI  Blockade  CoreOS  Quay.io  Orchard  OpenShift
• 14.
  Other nice features Trusted images on index.docker.io  Logs of exited containers  Caching of images for repeat builds  Docker daemon and REST API
• 15.
  Tips for Use Heavy use of Environment variables  Look into fig, maestro, or coreos/fleet  Never refer to localhost  AUFS vs BTRFS