Intro to Docker + Tips on Using Docker with Rails Apps

Slide 1

Slide 1 text

ì Introduction to Docker + Tips on using Docker for Rails Apps Brian Morearty Feb 20, 2014

Slide 2

Slide 2 text

Your Host 15 Docker Tips in 5 Minutes 2

Slide 3

Slide 3 text

15 Docker Tips in 5 Minutes 3 •  Brian Morearty •  Rails consultant •  Docker partner:

Slide 4

Slide 4 text

What is Docker? 15 Docker Tips in 5 Minutes 4

Slide 5

Slide 5 text

Well, What is it NOT? 15 Docker Tips in 5 Minutes 5

Slide 6

Slide 6 text

Hands on with Docker 6 • It’s not like Chef or Puppet… • But…it does enable you to set up a machine with a script.

Slide 7

Slide 7 text

Hands on with Docker 7 • It’s not a VM… • But…it does run processes in an isolated environment from the host machine.

Slide 8

Slide 8 text

Ok, what IS it? 15 Docker Tips in 5 Minutes 8

Slide 9

Slide 9 text

Hands on with Docker 9 • Open source wrapper around Linux containers. • Lets you package, deploy, and run your app with its dependencies.

Slide 10

Slide 10 text

Hands on with Docker 10 • Similar to a VM (has snapshots etc.), but: • Doesn’t preallocate memory • Instant startup

Slide 11

Slide 11 text

Hands on with Docker 11 • The container relies on the host OS for: •  Process & thread management •  Memory allocaQon •  Networking •  Etc.

Slide 12

Slide 12 text

Hands on with Docker 12 • Does not rely on the host OS for: •  Dependencies (supporQng processes)

Slide 13

Slide 13 text

Hands on with Docker 13 • A Dockerﬁle is a script to create a Docker container •  It’s opQonal. •  You can just install stuﬀ in a command-‐line shell.

Slide 14

Slide 14 text

Hands on with Docker 14 • Containers are built in layers. •  File system is Copy-‐On-‐ Write •  Touch a byte in a ﬁle. Your ﬁle gets copied up to the current layer.

Slide 15

Slide 15 text

Hands on with Docker 15 • Layers are cool. •  Build containers on containers. •  Stand on shoulders.

Slide 16

Slide 16 text

Sample use cases 15 Docker Tips in 5 Minutes 16

Slide 17

Slide 17 text

Hands on with Docker 17 • Easier developer machine setup with lots of dependencies •  Whether in a corp environment •  Or make it easier to contribute to your open source project

Slide 18

Slide 18 text

Hands on with Docker 18 • Easier distribuQon & installaQon of your app •  Whether open or closed source

Slide 19

Slide 19 text

Hands on with Docker 19 • Set up your prod environment but you dislike Chef

Slide 20

Slide 20 text

Hands on with Docker 20 • Deploy in VMs but you want to have more RAM available

Slide 21

Slide 21 text

Hands on with Docker 21 • Separate conﬂicQng dependencies (openssl, ruby, etc.) among your apps and layers.

Slide 22

Slide 22 text

15 Docker Tips in 5 Minutes 22 SO LET’S SEE IT

Slide 23

Slide 23 text

(Skipping Past the Tutorial to Get to the Railsy Part…) 15 Docker Tips in 5 Minutes 23

Slide 24

Slide 24 text

15 Docker Tips in 5 Minutes 24 • A Dockerﬁle for a Rails app

Slide 25

Slide 25 text

15 Docker Tips in 5 Minutes 25 # This will build the handson-namer image! FROM ubuntu:12.10! MAINTAINER Your Name, [email protected]! ! # Install dependencies! RUN apt-get update! RUN apt-get install -y curl git \! build-essential ruby2.1.0! RUN gem install rubygems-update! RUN update_rubygems! RUN gem install bundler --no-ri --no-rdoc! ! # Rails uses this port ya know! EXPOSE 3000! ! # Copy the app into the container at build time! ADD namer /opt/namer! WORKDIR /opt/namer! RUN bundle install! ! # Set the startup command! CMD ["rails", "server"]!

Slide 26

Slide 26 text

15 Docker Tips in 5 Minutes 26 •  Takes minutes the ﬁrst Qme. •  Takes seconds the next Qme. •  Only re-‐executes any steps a]er the ﬁrst one that changed. ! $ docker build -t railsapp .!

Slide 27

Slide 27 text

15 Docker Tips in 5 Minutes 27 •  Run detached •  Map host port 80 to container port 3000 •  Except there’s no DB. Crash. ! $ docker run -d -p 80:3000 railsapp!

Slide 28

Slide 28 text

15 Docker Tips in 5 Minutes 28 • Now make a Dockerﬁle for a Postgres server •  Or at least part of one

Slide 29

Slide 29 text

15 Docker Tips in 5 Minutes 29 FROM ubuntu! MAINTAINER Alvin Lai ! ! RUN add-apt-repository ppa:pitti/postgresql! RUN apt-get -y update! ! ENV PG_VERSION 9.2! ENV LOCALE en_US! ENV LANGUAGE en_US.UTF-8! ENV LANG en_US.UTF-8! ENV LC_ALL en_US.UTF-8! ! RUN apt-get -y install postgresql-$PG_VERSION postgresql-client- $PG_VERSION postgresql-contrib-$PG_VERSION! ! RUN service postgresql start && \! su postgres sh -c "createuser -d -r -s docker" && \! su postgres sh -c "createdb -O docker docker" && \! su postgres sh -c "psql -c \"GRANT ALL PRIVILEGES ON DATABASE docker to docker;\""! ! EXPOSE 5432! CMD ["su", "postgres", "-c", "/usr/lib/postgresql/$PG_VERSION/bin/ postgres -D /var/lib/postgresql/$PG_VERSION/main/ -c config_file=/etc/ postgresql/$PG_VERSION/main/postgresql.conf"]! ! EXPOSE 5432!

Slide 30

Slide 30 text

15 Docker Tips in 5 Minutes 30 • It looks a lot like that last one. • But exposes port 5432.

Slide 31

Slide 31 text

15 Docker Tips in 5 Minutes 31 • Now, connect them. • How?

Slide 32

Slide 32 text

15 Docker Tips in 5 Minutes 32 • Names and Links.

Slide 33

Slide 33 text

15 Docker Tips in 5 Minutes 33 •  Run detached •  Name the container “pg” •  (The image is named postgres) •  Don’t use -p…it would expose port 5432 to the host. ! $ docker run -d -name pg postgres!

Slide 34

Slide 34 text

15 Docker Tips in 5 Minutes 34 •  Sets up a network bridge to pg •  Injects env vars in the railsapp container (pg’s ip addr, port mapping, etc.) ! $ docker run -d -p 80:3000 -link pg \! railsapp!

Slide 35

Slide 35 text

15 Docker Tips in 5 Minutes 35 •  conﬁg/database.yml production:! adapter: postgresql! database: railsapp_production! username: railsapp! host: <%=  ENV['PG_PORT_5432_TCP_ADDR'] %>! port: <%=  ENV['PG_PORT_5432_TCP_PORT'] %>! pool: 5! timeout: 5000!

Slide 36

Slide 36 text

Hands on with Docker 36 • It works. Try it. J

Slide 37

Slide 37 text

Hands on with Docker 37 • One last thing.

Slide 38

Slide 38 text

Using Docker with Rails apps: how to cache “bundle install” when the gems haven’t changed Hands on with Docker 38

Slide 39

Slide 39 text

Hands on with Docker 39 •  Problem: commands that depend on a configuraQon file will not be cached if: •  that file is part of an ADDed directory, and •  the directory tree contains other frequently-‐modified files. ‐︎ e.g., a Gemfile e.g., an app directory ‐︎ e.g., source files ‐︎ ‑︎︎ e.g., bundle install

Slide 40

Slide 40 text

FROM ubuntu:12.10! MAINTAINER Your Name, [email protected]! ! # Install system dependencies (cached)! RUN apt-get install ...! ! # Copy the app into the container! # (DOES NOT use cache when myapp changes)! ADD myapp /opt/myapp! WORKDIR /opt/myapp! RUN bundle install! ! # Set the startup command! CMD ["rails", "server"]! Hands on with Docker 40

Slide 41

Slide 41 text

Hands on with Docker 41 •  Change the app and rebuild the image. à bundle install can’t be cached. (Because the ADD invalidated the cache.) à must reinstall all dependency gems

Slide 42

Slide 42 text

Hands on with Docker 42 • Kinda defeats the purpose of the Docker cache

Slide 43

Slide 43 text

Hands on with Docker 43 • The soluNon: two ADDs. •  First add the Gemﬁle (and Gemﬁle.lock). •  Then bundle install. •  Then ADD the whole app.

Slide 44

Slide 44 text

FROM ubuntu:12.10! MAINTAINER Your Name, [email protected]! ! # Install system dependencies (cached)! RUN apt-get install ...! ! # Copy the Gemfile and Gemfile.lock! # (CACHED unless they changed)! ADD myapp/Gemfile /tmp/Gemfile! ADD myapp/Gemfile.lock /tmp/Gemfile.lock! WORKDIR /tmp! RUN bundle install! ! # Now copy the app into the container! ADD myapp /opt/myapp! WORKDIR /opt/myapp! ! # Set the startup command! CMD ["rails", "server"]! Hands on with Docker 44 Before ADDing the app

Slide 45

Slide 45 text

Hands on with Docker 45 • Finally…

Slide 46

Slide 46 text

For videos and exercises, buy the self-‐paced Hands on with Docker class. In partnership with Docker, Inc. handsonwith.com 15 Docker Tips in 5 Minutes 46