Docker Container Basics and Benefits

Dr Ganesh Neelakanta Iyer
July 2015

Disclaimer:
I do not have any working experience with Docker or containers. The
slides are prepared based on my reading for last two weeks.
Consider this as a mutual sharing session. It may give you some
basic understanding of Dockers and containers

© 2015 Progress Software Corporation. All rights reserved.3
Multiplicityof
Goods
Multipilicityof
methodsfor
transporting/storing
DoIworryabout
howgoodsinteract
(e.g.coffeebeans
nexttospices)
CanItransport
quicklyandsmoothly
(e.g.fromboatto
traintotruck)
Cargo Transport Pre-1960

? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?
Also an NxN Matrix

Multiplicityof
Goods
Multiplicityof
methodsfor
transporting/storing
DoIworryabout
howgoodsinteract
(e.g.coffeebeans
nexttospices)
CanItransport
quicklyand
smoothly
(e.g.fromboatto
traintotruck)
Solution: Intermodal Shipping Container
…in between, can be loaded and
unloaded, stacked, transported
efficiently over long distances,
and transferred from one mode
of transport to another
A standard container that is
loaded with virtually any
goods, and stays sealed until
it reaches final delivery.

This eliminated the NXN problem…

and spawned an Intermodal Shipping Container Ecosystem
• 90% of all cargo now shipped in a standard container
• Order of magnitude reduction in cost and time to load and unload ships
• Massive reduction in losses due to theft or damage
• Huge reduction in freight cost as percent of final goods (from >25% to <3%) massive globalizations
• 5000 ships deliver 200M containers per year

What is Docker?
Docker is an open-source project that
automates the deployment
of applications inside software
containers, by providing an additional
layer of abstraction and automation
of operating system–level
virtualization on Linux.
[Source: en.wikipedia.org]
Docker allows you to package an
application with all of its
dependencies into a standardized unit
for software development.
[www.docker.com]
http://altinvesthq.com/news/wp-content/uploads/2015/06/container-ship.jpg

Static website
Web frontend
User DB
Queue Analytics DB
Background workers
API endpoint
nginx 1.5 + modsecurity + openssl + bootstrap 2
postgresql + pgv8 + v8
hadoop + hive + thrift + OpenJDK
Ruby + Rails + sass + Unicorn
Redis + redis-sentinel
Python 3.0 + celery + pyredis + libcurl + ffmpeg + libopencv + nodejs +
phantomjs
Python 2.7 + Flask + pyredis + celery + psycopg + postgresql-client
Development VM
QA server
Public Cloud
Disaster recovery
Contributor’s laptop
Production Servers
The Challenge
Multiplicityof
Stacks
Multiplicityof
hardware
environments
Production Cluster
Customer Data Center
Doservicesand
appsinteract
appropriately?
CanImigrate
smoothlyand
quickly?

Results in N X N compatibility nightmare
Static website
Web frontend
Background workers
User DB
Analytics DB
Queue
Development
VM
QA Server
Single Prod
Server
Onsite
Cluster
Public Cloud
Contributor’s
laptop
Customer
Servers
? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?

Static website Web frontendUser DB Queue Analytics DB
Development
VM
QA server Public Cloud Contributor’s
laptop
Docker is a shipping container system for code
Multiplicityof
Stacks
Multiplicityof
hardware
environments
Production
Cluster
Customer Data
Center
Doservicesand
appsinteract
appropriately?
CanImigrate
smoothlyand
quickly
…that can be manipulated using
standard operations and run
consistently on virtually any
hardware platform
An engine that enables any
payload to be encapsulated
as a lightweight, portable,
self-sufficient container…

Static website Web frontendUser DB Queue Analytics DB
Development
VM
QA server Public Cloud Contributor’s
laptop
Or…put more simply
Multiplicityof
Stacks
Multiplicityof
hardware
environments
Production
Cluster
Customer Data
Center
Doservicesand
appsinteract
appropriately?
CanImigrate
smoothlyand
quickly
Operator: Configure Once, Run
Anything
Developer: Build Once, Run
Anywhere (Finally)

Static website
Web frontend
Background workers
User DB
Analytics DB
Queue
Development
VM
QA Server
Single Prod
Server
Onsite
Cluster
Public Cloud
Contributor’s
laptop
Customer
Servers
Docker solves the NXN problem

Docker containers
 Wrap up a piece of software in a complete file system
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

Why containers matter
Physical Containers Docker
Content Agnostic The same container can hold almost
any type of cargo
Can encapsulate any payload and its
dependencies
Hardware Agnostic Standard shape and interface allow
same container to move from ship to
train to semi-truck to warehouse to
crane without being modified or
opened
Using operating system primitives (e.g.
LXC) can run consistently on virtually
any hardware—VMs, bare metal,
openstack, public IAAS, etc.—without
modification
Content Isolation and
Interaction
No worry about anvils crushing
bananas. Containers can be stacked
and shipped together
Resource, network, and content
isolation. Avoids dependency hell
Automation Standard interfaces make it easy to
automate loading, unloading, moving,
etc.
Standard operations to run, start, stop,
commit, search, etc. Perfect for devops:
CI, CD, autoscaling, hybrid clouds
Highly efficient No opening or modification, quick to
move between waypoints
Lightweight, virtually no perf or start-up
penalty, quick to move and manipulate
Separation of duties Shipper worries about inside of box,
carrier worries about outside of box
Developer worries about code. Ops
worries about infrastructure.

Docker containers
Lightweight
• Containers running on
one machine all share
the same OS kernel
• They start instantly
and make more
efficient use of RAM
• Images are
constructed from
layered file systems
• They can share
common files, making
disk usage and image
downloads much
more efficient
Open
• Based on open
standards
• Allowing containers to
run on all major Linux
distributions and
Microsoft OS with
support for every
infrastructure
Secure
• Containers isolate
applications from
each other and the
underlying
infrastructure while
providing an added
layer of protection for
the application

Docker / Containers vs. Virtual Machine
https://www.docker.com/whatisdocker/
Containers have similar resource isolation
and allocation benefits as VMs but a
different architectural approach allows them
to be much more portable and efficient

Docker / Containers vs. Virtual Machine
https://www.docker.com/whatisdocker/
• Each virtual machine includes the application,
the necessary binaries and libraries and an
entire guest operating system - all of which
may be tens of GBs in size
• It includes the application and all of its
dependencies, but share the kernel with other
containers.
• They run as an isolated process in userspace
on the host operating system.
• Docker containers run on any computer, on
any infrastructure and in any cloud

Why are Docker containers lightweight?
Bins/
Libs
App
A
Original App
(No OS to take
up space, resources,
or require restart)
AppΔ
Bins
/
App
A
Bins/
Libs
App
A’
Gues
t
OS
Bins/
Libs
Modified App
Union file system allows
us to only save the diffs
Between container A
and container
A’
VMs
Every app, every copy of an
app, and every slight modification
of the app requires a new virtual server
App
A
Guest
OS
Bins/
Libs
Copy of
App
No OS. Can
Share bins/libs
App
A
Guest
OS
Guest
OS
VMs Containers

What are the basics of the Docker system?
Source
Code
Repository
Dockerfile
For
A
Docker Engine
Docker
Container
Image
Registry
Build
Docker Engine
Host 2 OS 2 (Linux)
Container
A
Container
B
Container
C
ContainerA
Push
Search
Pull
Run
Host 1 OS
(Linux)

Changes and Updates
Docker Engine
Docker
Container
Image
Registry
Docker Engine
Push
Update
Bins/
Libs
App
A
AppΔ
Bins
/
Base
Container
Image
Host is now running A’’
Container
Mod A’’
AppΔ
Bins
/
Bins/
Libs
App
A
Bins
/
Bins/
Libs
App
A’’
Host running A wants to upgrade to A’’.
Requests update. Gets only diffs
Container
Mod A’

How does this help you build better software?
• Stop wasting hours trying to setup developer environments
• Spin up new instances and make copies of production code to run locally
• With Docker, you can easily take copies of your live environment and run on any new
endpoint running Docker.
Accelerate Developer Onboarding
• The isolation capabilities of Docker containers free developers from the worries of using
“approved” language stacks and tooling
• Developers can use the best language and tools for their application service without
worrying about causing conflict issues
Empower Developer Creativity
• By packaging up the application with its configs and dependencies together and shipping
as a container, the application will always work as designed locally, on another machine,
in test or production
• No more worries about having to install the same configs into a different environment
Eliminate Environment Inconsistencies

Easily Share and Collaborate on Applications
 Distribute and share content
• Store, distribute and manage your Docker images in your Docker
Hub with your team
• Image updates, changes and history are automatically shared
across your organization.
 Simply share your application with others
• Ship your containers to others without worrying about different
environment dependencies creating issues with your application.
• Other teams can easily link to or test against your app without
having to learn or worry about how it works.
Docker creates a common framework for developers and sysadmins to work
together on distributed applications

Get Started with Docker
 install Docker
 run a software image in a container
 browse for an image on Docker Hub
 create your own image and run it in a container
 create a Docker Hub account and an image repository
 create an image of your own
 push your image to Docker Hub for others to use
http://docs.docker.com/windows/started/

• The Life of a Container
– Conception
• BUILD an Image from a Dockerfile
– Birth
• RUN (create+start) a container
– Reproduction
• COMMIT (persist) a container to a new image
• RUN a new container from an image
– Sleep
• KILL a running container
– Wake
• START a stopped container
– Death
• RM (delete) a stopped container
• Extinction
– RMI a container image (delete image)
Docker Container Lifecycle ……

How a command looks like

Docker Compose
 Compose is a tool for defining and running multi-container applications with Docker
 With Compose, you define a multi-container application in a single file, then spin your
application up in a single command which does everything that needs to be done to get
it running
 Compose is great for development environments, staging servers, and CI. We don’t
recommend that you use it in production yet
Define your app’s environment with a Dockerfile so it can be reproduced
anywhere.
Define the services that make up your app in docker-compose.yml so
they can be run together in an isolated environment:
Lastly, run docker-compose up and Compose will start and run your
entire app.

Video
 https://www.youtube.com/watch?v=GVVtR_hrdKI

Health and fitness Mobile App

A familiar story
 You’ve been tasked with creating the REST API for a mobile app for tracking health and
fitness
 You code the first endpoint using the development environment on your laptop
 After running all the unit tests and seeing that they passed, you check your code into
the Git repository and let the QA engineer know that the build is ready for testing
 The QA engineer dutifully deploys the most recent build to the test environment, and
within the first few minutes of testing discovers that your recently developed REST
endpoint is broken
 After spending a few hours troubleshooting alongside the QA engineer, you discover
that the test environment is using an outdated version of a third-party library, and this is
what is causing your REST endpoints to break
Slight differences between development, test, stage, and production
environments can wreak mayhem on an application
https://medium.com/aws-activate-startup-blog/a-better-dev-test-experience-docker-and-aws-291da5ab1238

Solution
 Traditional approaches for dealing with this problem, such as change management
processes, are too cumbersome for today’s rapid build and deploy cycles
 What is needed instead is a way to transfer an environment seamlessly from
development to test, eliminating the need for manual and error prone resource
provisioning and configuration.
 You can create Docker images from a running container, similar to the way we create
an AMI from an EC2 instance. For example, one could launch a container, install a
bunch of software packages using a package manager like APT or yum, and then
commit those changes to a new Docker image.
Solution  Containers (Docker)

Back to story
 First, define a Docker image for launching a container for
running the REST endpoint
 Use this to test our code on a laptop, and the QA
engineer can use this to test the code in EC2
 The REST endpoints are going to be developed using
Ruby and the Sinatra framework, so these will need to be
installed in the image
 The back end will use Amazon DynamoDB
 To ensure that the application can be run from both inside
and outside AWS, the Docker image will include the
DynamoDB local database.

Selenium Grid and Docker

Selelnium Grid and Docker
 Selenium Grid is a great way to speed up your tests by running them in parallel on
multiple machines
 However, rolling your own grid also means maintaining it
 Setting up the right browser / OS combinations across many virtual machines (or –
even worse – physical machines) and making sure each is running the Selenium
Server correctly is a huge pain
 Not to mention troubleshooting when something goes wrong on an individual node
 God help you when it comes time to perform any updates
Thinking about this problem, it’s clear we need a central point from where we can configure and
update our hub / nodes. It would also be great if we had a way to quickly recover in case an
individual node crashes or otherwise ends up in a bad state.
Selenium Grid is distributed system of nodes for running tests. Instead of running your grid across
multiple machines or VMs, you can run them all on a single large machine using Docker.

Selelnium Grid and Docker
 Docker Compose lets take our Docker images and spin them up as a pre-configured
Selenium Grid cluster
 Selenium Grid handles the routing of your tests to the proper place, Docker lets you
configure your browser / OS combinations in a programmatic way, and Compose is the
central point from which you can spin everything up on the fly.
 A huge benefit of using Docker is its capacity to scale
• Running Selenium Grid on separate machines or even a set of VMs requires a lot of
unnecessary computing overhead
• Docker images run as userspace processes on a shared OS; so your images share some
system resources, but are still isolated and require far fewer resources to run than a VM
• This means you can cram more nodes into a single instance

How to Run Your Selenium Grid with Docker
Create Docker images for your Selenium Grid hub and node(s)
Add Java to the hub to run the Selenium server jar
Add Java, plus Firefox and Xvfb to the node
Create a docker-compose.yml file to define how the images will
interact with each other
Start docker-compose and scale out to as many nodes as you
need – or that your machine can handle
http://www.conductor.com/nightlight/running-selenium-grid-using-docker-compose/
https://sandro-keil.de/blog/2015/03/23/selenium-grid-in-minutes-with-docker/

How PLOS uses Docker for Testing

PLOS and Docker
 PLOS  Library of open access journals and other scientific
literature under an open content license
 When PLOS has grown in terms of users, articles and developers,
they decided to split their original applications into web services
 They created test environments that mimic production using
Docker containers
• Docker makes it quick and easy to narrow the gap between production
and development

PLOS uses Docker for amazing test experience
• To run the API tests, they point them at port 8080, and they are testing the
Dockerized API instead of a service running directly on the host
• A few small scripts are written that orchestrate bringing those containers up and
down as needed between various tests and
Black Box Testing
• Use compose to bring up any number of instances of the services in your stack
• docker-compose scale web=10 database=3
• PLOS have seen hundreds of database containers run on a single laptop with
no problem
Scalability Testing
• Easy to add very invasive automated tests for testing configurations
Configuration Testing

More for QA

Security Testing using Docker
 ZAP is an intercepting proxy
 Download a docker image from
https://code.google.com/p/zaproxy/wiki/Docker
 Run ZAP inside a container and acting as a proxy for testing
 You can configure your browser to connect through the ZAP proxy
on 127.0.0.1:8080 and start to playHTTP and HTTPS connections

Distributed Performance Testing using JMeter and Docker
 Instead of JMeter running on VMs, create
Docker images
 Docker also has the ability to iterate, correct and
improve on an existing image
 Some of the key advantages of using Docker
here:
• Creating and modifying Docker image is fast and
easy
• Since the JMX and data files were maintained on
the host a change in these files simply means
restart the container
• Creating additional JMeter server instance is just
a matter of another docker run invocation
• Finally startup time will be almost imperceptible

References
 Testing made awesome with Docker at PLOS
• http://blogs.plos.org/tech/testing-made-awesome-with-docker/
 Functional Testing with Docker
• http://www.rounds.com/blog/functional-testing-docker/
 Distributed JMeter testing using Docker
• http://srivaths.blogspot.in/2014/08/distrubuted-jmeter-testing-using-docker.html
 Security Testing using Docker
• http://www.ojscurity.com/2015/02/docker-zed-attack-proxy-with-tor.html
 Video on testing using Docker
• https://www.youtube.com/watch?v=B-nv8EO1Mwk

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