docker-next-big-thing

Docker - next big thing

By @jwo for HoustonRB

Docker

• Run in linux, just like production
• It's like heroku, for development

Laws of Docker

• 1 Process per Container
• "Containers" are servers

Standard Rails App

• Rails
• PostgreSQL
• Redis
• Memcached
• Sidekiq

Startup - Development

• Clone
• bundle
• rake db:setup
• brew install postgresql
• createdb
• brew install redis
• brew install memcached
• foreman start

Startup - Production

• install ruby from source. maybe rbenv?
• sudo apt-get install postgresql, redis, memcached
• bundle
• create database and user
• rake db:migrate
• configure nginx and unicorn

ETOOMANYDIFFS

New users, many dependencies, such frustration

Startup, Dev and Live

Comparison vs Chef

• No need for chef or ansible for most cases
• Deploy and you're good

Docker Compose

• Was "fig" (older documentation)
• Fancy term: "Coordination"
• Real World: connects your DB to your Rails

docker-compose.yml

mysqldata:
  image: cogniteev/echo
  volumes:
    - /var/lib/mysql

db:
  build: mysql:latest
  expose:
    - "3306"
  volumes_from:
    - mysqldata

app:
  build: .
  command: bundle exec rails s -p 3000 -b '0.0.0.0'
  volumes:
    - .:/myapp
  ports:
    - "3000:3000"
  links:
    - db

Boot2docker

Have to have it so your Macs can run Linux in your Linux

HOWTO Persist Data

(Like Postgres, etc Data)

• Have your db data directory connect to a "data container"

mysqldata:
  image: cogniteev/echo
  volumes:
    - /var/lib/mysql

db:
  build: mysql:latest
  expose:
    - "3306"
  volumes_from:
    - mysqldata

HOWTO Deploy your docker

• SSH into your main box
• git clone
• docker-compose build
• docker-compose stop && docker-compose start

HOWTO Get a main box with docker

HOWTO Edit your Rails locally

• Do everything the same except: http://192.168.59.103:3000/ instead of http://localhost:3000

HOWTO run migrations

docker-compose run app rake db:migrate

HOWTO Environment files

Add in a .env file like you normally would. Gitignore it.

mysql:
  env_file: DockerConfig/.env
  volumes_from:
    - mysqldatacontainer

HOWTO database.yml

production:
  adapter: mysql2
  database: yolo_production
  username: <%= ENV['MYSQL_USER']%>
  password: <%= ENV['MYSQL_PASS']%>
  host: mysql
  port: 3306

HOWTO SSH into your boxes

docker-compose run app /bin/bash

HOWTO Monitor your boxes

Prometheus, by SoundCloud folk, rules.

prometheus:
  build: docker_config/prometheus
  ports:
    - "9090:9090"
  links:
    - containerexporter

containerexporter:
  image: prom/container-exporter
  ports:
    - "9104:9104"
  volumes:
    - /sys/fs/cgroup:/cgroup
    - /var/run/docker.sock:/var/run/docker.sock

DockerFile

FROM phusion/passenger-ruby22
RUN apt-get update -qq && apt-get install -y build-essential

RUN mkdir /myapp
WORKDIR /myapp
ADD . /myapp
RUN bundle install

Services

• Docker intentionally breaks upstart and most things that start systems
• The Dockerfile, instead, has a "CMD" (one cmd) that runs when started
• This is basically the docker way

HOWTO Run more than one service

(assuming you want to say, run Inspeqtor to notify you of crashes)

• Install runit (pronounced 'run-it')
• CMD is "/usr/sbin/runsvdir-start"

# Add runit startups
RUN mkdir /etc/sv/inspeqtor
ADD inspeqtor.runit /etc/sv/inspeqtor/run
RUN mkdir /etc/sv/mysql
ADD mysql.runit /etc/sv/mysql/run
RUN chmod +x /etc/sv/inspeqtor/run
RUN chmod +x /etc/sv/mysql/run
# Link runit startup scripts
RUN ln -s /etc/sv/mysql/ /etc/service/mysql
RUN ln -s /etc/sv/inspeqtor/ /etc/service/inspeqtor

# remove the upstart config directory
RUN rm -rf /etc/init

Yeah

• So that part is rough around the edges
• Docker REALLY wants you to do 1 process per container
• It strips all else away besides what you start
• But runit can work

Finding Images

Images are on https://registry.hub.docker.com/

HOWTO Reverse Engineer Dockerfiles

Ubuntu. CoreOS. Debian. (likely more).

JWO Rule of Docker Images

What if I told you that using other people's (even official) docker images lead to more problems than they solve?

HOWTO Scale number of app servers

upstream app_servers {
  server 127.0.0.1:8080;
  server 127.0.0.1:8081;
}

Possible way to automate: http://jasonwilder.com/blog/2014/03/25/automated-nginx-reverse-proxy-for-docker/

HOWTO Have a larger disk size on boot2docker

boot2docker destroy
boot2docker init --disksize=20000

(Yeah, that deletes all stuff and you start over)

HOWTO See what's running, and stop them

docker ps

CONTAINER ID        IMAGE                    COMMAND                CREATED STATUS              PORTS               NAMES
555b3b4e31fa        fivehundred_app:latest   "bundle exec rails s   2 minutes ago       Up 2 minutes        80/tcp, 443/tcp     fivehundred_app_1   
6a5bb766f745        postgres:latest          "/docker-entrypoint.   2 minutes ago       Up 2 minutes        5432/tcp            fivehundred_db_1

docker kill 555b3b4e31fa

Demo

Conclusion

Try it out:

GitHub / jwo / blocker