Using Docker to build and test in your laptop and Jenkins

Using Docker to
build and test in
laptop and
Jenkins
Micael Gallego
micael.gallego@urjc.es
@micael_gallego
https://goo.gl/syUwZp
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@micael_gallego
micael.gallego@urjc.es
@micaelgallego
About me
developer
University professor
Trainer & Consultor

Consultancy / Training
Cloud Computing
WebTechnologies
Extreme Programming
Testing / Git / Jenkins
Software Architecture
Concurrent Programming
Open source elastic platform
for end to end testing
http://codeurjc.es http://elastest.io
Advanced log management
Test orchestration
Test execution comparison
Web and Mobile testing
Security testing
IoT testing
Performance testing

Virtualizacion and Containers
● Developers want to reduce the
differences between local,
continuous integration and
production environments
● Avoiding “It works in my machine”
type of problems
Virtualization Containers

Virtualizacion and Containers
● Virtualization
– Full fledged Virtual Machine (VirtualBox)
– Developer friendly managed VM
(Vagrant)
● Containers
– Docker

VirtualBox
● Developed by Oracle (was owned by Sun
Microsystems)
● Mostly open source, several free (but closed
source) modules
● Windows, Linux and Mac versions
● Advanced Desktop Virtualization
– Shared folders host / guest
– Keyboard and mouse advanced integration
– Graphic 3D acceleration
– Webcam
https://www.virtualbox.org/

VirtualBox
● Manual
– Create an empty virtual machine
– Connect to a ISO (simulating real CD
devide)
– Install a full fledged Operating System
– It is time consuming and it is not easy
to share VM between developers

Vagrant
● It is a command line utility to manage
VMs
● It makes very easy to download and start
a new VM (only with a command)
● Allows to provisioning the new VM with
command provisioning tools (script, chef,
puppet, ansible…)
● VM configuration is specified in a text file,
allowing to share it in the git repository
https://www.vagrantup.com/

Vagrant
● How to create a new VM with ubuntu Xenial
● Vagrant manages certificates and networking
to make easy to connect to the new VM
● By default, working dir is shared
with VM
$ vagrant init ubuntu/xenial64
$ vagrant up
$ vagrant ssh

containers
https://www.docker.com/

Docker
● With VMs you can have the production
environment in your laptop
● But…
– VMs takes minutes to start up
– VMs use (waste?) a lot of resources
(memory and disk space)

Docker
● In a first look, containers can be
considered as “lightweight VMs”
– They contain an isolated environment to run
apps
– Start in milliseconds
– They use only the resources it needs
– A container doesn't have a full fledged
operating system, only the minimal
software to execute apps

Docker
●
Containers and VMs are very different
Virtual Machines Containers
Heavier Lighter
Execute several processes per
Virtual Machine
Usually execute only one process
per container
Ssh connection Direct execution in the container
(rarely needed)
More isolated using hypervisor Less isolated because are
executed using kernel features
Can virtualizeWindows over
Linux
Linux containers must be
executed in linux hosts*
* More on that later

Docker
● To install an application in a linux system you
need all dependencies installed
● Can be incompatibilities between applications
that need different version of the same
dependency
● Docker include in a container all needed
software isolated to the rest of the system

Docker
● Docker containers SO support
– Linux containers
● Very mature technology
● It can be used in any* linux distribution
– Windows containers
● Preliminary technology
● It only can be used in a very recent**
Windows Server version
* Kernel version 3.10 or greather. Published in June 2013
**Windows Server 2016 (Core and with Desktop Experience), Nano Server, andWindows 10
Professional and Enterprise (Anniversary Edition).

Docker
● You can execute linux containers in
any operating system
● It uses virtualization (under the
covers) in Mac and Windows

Docker
● Docker Toolbox for Mac and Windows
– It uses VirtualBox as virtualization
– It is not the same development experience
than in linux
● Docker for Mac and Windows
– Uses native virtualization technology in each
operating system
– Only available in new versions of that SOs

•Docker Image
– Basic template for a container (hard disk of
VM)
– It contains SO (ubuntu), libs (Java) and app
(webapp.jar)
– A container always is started from an image
– If you want to start a new container from an
image that is not in your system, it is
automatically downloaded from Internet
Docker concepts

•Docker Registry
●
Remote service used to store and retrive docker
images
●
It can hold several versions of the same image
●
All versions of the same image are located in the
same repository (like in git)
●
Docker Hub is a public registry managed by Docker
Inc.
●
You can buy private repositories in Docker Hub
●
You can also operate your own private registry
Docker concepts

•Popular repositories in Docker Hub
Docker concepts

•Docker Container
– It is the “equivalent” of a Virtual Machine
– A container is created from a docker image
– When a file is wrote, the image it is not
modified, the container is modified
– It can be started, paused or
stopped
Docker concepts

•Docker Engine
– Local service used to control docker
– Manages images (download, create, pull,
push…)
– Manages containers (start, stop, commit...)
– It can be used with the docker client or
using its REST API
Docker concepts

•Docker client
– Command line interface (CLI) tool to
control docker engine
– It is available when docker is installed in a
system to connect to their local docker
engine
Docker concepts

•Official documentation
– https://docs.docker.com/
•Advanced tutorials
– https://docs.docker.com/engine/tutorials/dockerizing/
– https://docs.docker.com/engine/tutorials/usingdocker/
– https://docs.docker.com/engine/tutorials/dockerimages/
– https://docs.docker.com/engine/tutorials/networkingcontainers/
– https://docs.docker.com/engine/tutorials/dockervolumes/
– https://docs.docker.com/engine/tutorials/dockerrepos/
●
Cheat Sheet
– https://github.com/wsargent/docker-cheat-sheet/blob/master/README.md
Docker documentation

First steps with docker
Install Docker
– Windows:
● Microsoft Windows 10 Professional or Enterprise 64-bit:
https://store.docker.com/editions/community/docker-ce-desktop-windows
● Other Windows versions: https://www.docker.com/products/docker-toolbox
– Linux:
● Ubuntu: https://store.docker.com/editions/community/docker-ce-server-ubuntu
● Fedora: https://store.docker.com/editions/community/docker-ce-server-fedora
● Debian: https://store.docker.com/editions/community/docker-ce-server-debian
● CentOS: https://store.docker.com/editions/community/docker-ce-server-centos
– Mac:
● Apple Mac OS Yosemite 10.10.3 or above:
https://store.docker.com/editions/community/docker-ce-desktop-mac
● Older Mac: https://www.docker.com/products/docker-toolbox

Hands on…
https://github.com/docker/labs/tree/master/beginner

Testing if docker is correctly installed
$ docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
03f4658f8b78: Pull complete
a3ed95caeb02: Pull complete
Digest:
sha256:8be990ef2aeb16dbcb9271ddfe2610fa6658d13f6dfb8bc72074cc1ca369
66a7
Status: Downloaded newer image for hello-world:latest
Hello from Docker.
This message shows that your installation appears to be working
correctly.
...

Running your first container
$ docker run alpine ls -l
total 48
drwxr-xr-x 2 root root 4096 Mar 2 16:20 bin
drwxr-xr-x 5 root root 360 Mar 18 09:47 dev
drwxr-xr-x 13 root root 4096 Mar 18 09:47 etc
drwxr-xr-x 2 root root 4096 Mar 2 16:20
home
drwxr-xr-x 5 root root 4096 Mar 2 16:20 lib
......
......

Command “run”
Creates a new
container and start it

Image name
alpine is a minimal linux system
(4.8Mb).The image is downloaded if
not stored in local machine

Command “ls -l”
This command will be
executed inside the
running container

Inspecting the downloaded images
$ docker images
REPOSITORY TAG IMAGE ID
CREATED VIRTUAL SIZE
alpine latest c51f86c28340
4 weeks ago 1.109 MB
hello-world latest 690ed74de00f
5 months ago 960 B
List all images stored in the system

Executing a container
$ docker run alpine echo "hello from alpine"
hello from alpine
Execute the command “echo” inside the container

Inspecting containers (executing)
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED
STATUS PORTS NAMES
a6a9d46d0b2f alpine "echo 'hello from alp" 6 minutes
ago Exited (0) 6 minutes ago lonely_kilby
ff0a5c3750b9 alpine "ls -l" 8 minutes
ago Exited (0) 8 minutes ago elated_ramanujan
c317d0a9e3d2 hello-world "/hello" 34 seconds
ago Exited (0) 12 minutes ago stupefied_mcclintock
It shows containers in the system.
All of them has STATUS Exited.These containers are
not currently executing (but using disk space)

Interactive commands in containers
$ docker run -it alpine /bin/sh
/ # ls
bin dev etc home lib linuxrc media mnt proc
root run sbin sys tmp usr var
/ # uname -a
Linux 97916e8cb5dc 4.4.27-moby #1 SMP Wed Oct 26 14:01:48 UTC 2016 x86_64
Linux
/ # exit
$
To execute an interactive command it is necessary to
use the option “-it” to connect the console to the
container command

● Interactive commands in containers
– When you execute a /bin/sh command in
a container it offers a “similar” experience
than a ssh connection
– Buy there are no ssh server neither ssh
client
– It is executing a shell inside the
container

● Managing containers lifecycle
$ docker run -d seqvence/static-site
Option “-d”
Executes the container
in background

$ docker ps
CONTAINER ID IMAGE COMMAND
CREATED STATUS PORTS NAMES
a7a0e504ca3e seqvence/static-site "/bin/sh -c 'cd /usr/"
28 seconds ago Up 26 seconds
Container id is
a7a0e504ca3e
This id is used to refer to
this container
STATUS is UP

– Stop running container
– Delete files of the stopped container
$ docker stop a7a0e504ca3e
$ docker rm a7a0e504ca3e

Net services with docker
● Start container exposing a port
docker run --name static-site
-e AUTHOR="Your Name" -d
-p 9000:80 seqvence/static-site

--name static-site
Specifies a unique name
for the container

-e AUTHOR="Your Name"
Set the environment variable
AUTHOR to value “Your Name”

-d
Execute container as deamon

-p 9000:80
Connects the host port 9000 to
the port 80 in the container

● Use the service
– Open http://127.0.0.1:9000 in a browser in
your host to access 80 port in container

● Use the service
– If you are using Docker Toolbox for Mac or
Windows you can’t use 127.0.0.1 IP
– Then you have to open
http://192.168.99.100:9000/ in the browser
$ docker-machine ip default
192.168.99.100

● Container management
– Stop and remove the container
– Stop and remove a running container
– Remove all running containers
$ docker rm -f static-site
$ docker stop static-site
$ docker rm static-site
$ docker rm -f $(docker ps -a -q)

Managing docker images
● List images in host
Tag is like “version”. Latest is… the
latest ;)
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
seqvence/static-site latest 92a386b6e686 2 hours ago 190.5 MB
nginx latest af4b3d7d5401 3 hours ago 190.5 MB
python 2.7 1c32174fd534 14 hours ago 676.8 MB
postgres 9.4 88d845ac7a88 14 hours ago 263.6 MB
Containous/traefik latest 27b4e0c6b2fd 4 days ago 20.75 MB
...

● Managing versions
– Download a concrete version
– Download latest version
$ docker pull ubuntu:12.04
$ docker pull ubuntu

● Searching images in DockerHub

● Searching images in Docker Store

● Image types
– Base images
● Images without a parent image
● Examples: Ubuntu, debian, alpine…
● Used by Operating Systems
– Child images
● Base images plus some additional software
● Examples: Nginx, Apache, MySQL...

● Official vs User images
– Official images
● Images created by trusted
companies or communities
– User images
● Any user can create an account and
upload her own images

● Create your first image
– We will create a web application for display
random cat pics using Python
– Create a folder called flask-app
– Download all files in this URL to the folder
https://github.com/docker/labs/tree/master/beginner/flask-app

● Create your first image
– You have all source files for the web
application
– But you need Python and Flask to execute
the app
– To execute the web application, you will
create a new image with dependencies
(Python and Flask) and your application code
– Then you can create a new container to
execute your application

● Dockerfile
– File used to describe a new image
– Specifies
● Base image
● Commands to execute in the image
● Files to include in the image from the
project folder
● Open ports
● Command to execute when start the image

# Select base image
FROM alpine:latest
# Install python and pip
RUN apk add update pypip
RUN pip install upgrade pip
# copy app files
COPY app.py /usr/src/app/
COPY templates/index.html /usr/src/app/templates/
COPY requirements.txt /usr/src/app/
# install Python modules needed by the app
RUN pip install nocachedir r
/usr/src/app/requirements.txt
# tell the port number the container should expose
EXPOSE 5000
# run the application
CMD ["python", "/usr/src/app/app.py"]

● Dockerfile
– FROM: Base image
– COPY: Copy files from Dockerfile folder
– RUN execute commands
– EXPOSE: Public ports
– CMD: Command to execute when
container is started
https://docs.docker.com/engine/userguide/eng-
image/dockerfile_best-practices/

● Build the image
– In the folder with a Dockerfile execute
– Executed actions
● Create a new container with base image
● Execute commands and copy app files
● Create a new container with the result
$ docker build -t myfirstimage .

● Run the new image
– Open http://127.0.0.1:9000/ in the browser
– Windows and Mac users with Toolbox use the IP
$ docker run -p 9000:5000 myfirstimage
* Running on http://0.0.0.0:5000/
(Press CTRL+C to quit)

● Build the image again
– Change some HTML in templatesindex.html
– Create the image again
– The Dockerfile steps without changes are not re-
executed (are reused from previous execution)
– The image is created very quickly because only
the files copy is perfomed
$ docker build -t myfirstimage .

Volumes
● Volumes
– Allow sharing files between host and container
– Execute a container to show an nonexistent file
– Create a text file
$ docker run alpine cat /data/file.txt
cat: can't open '/data/file.txt': No such
file or directory
$ echo "My file" >> file.txt

Volumes
Volumes
● Mount a host folder inside a container folder
● Host contents replace container contents of
that folder
● Containers can write files in volumes to be
available in the host
$ sudo docker run -v $PWD:/data alpine
cat /data/file.txt
My file

Volumes
● Volumes
– Docker images use volumes to read files
from host
– Official NGINX container can serve host
files using http
● Serving current folder files ($PWD)
● Go to http://127.0.0.1:9000/file.txt
https://hub.docker.com/_/nginx/
$ docker run -p 9000:80 -v
$PWD:/usr/share/nginx/html:ro -d nginx

Volumes
● Volumes
– Docker Toolbox for Win or
Mac only allow folders
inside user folder to be
used as volume
– You can use other folders
but have to configure
shared folders in
VirtualBox
https://hub.docker.com/_/nginx/

•Containers main use cases
– Net service
●
Executed in background long time...
●
Used through network
●
Ex: Databases, web servers...
– Command
●
Execute a single command and stop
●
Read and write files from host with volumes
●
Ex: Java Compiler, jekyll, ffmpeg...
Docker container usage

•Docker for building software
– A container can have all needed environment to
execute a developer tool
– For example, you can have the compiler and the
test dependencies in a container
– You can clone a git repository and execute the
(dockerized) compiler without install any
software in your host
Docker for software developers

•Dockerized Java Maven
– Clone a maven repo
– Compile and exec tests
$ git clone
https://github.com/jglick/simple-maven-project-with-tests.git
$ cd simple-maven-project-with-tests
$ docker run --rm -v $PWD:/data -w /data maven mvn package

https://hub.docker.com/_/maven/
--rm
Remove container when
execution finish

--w
Working dir for the command

maven
Official Maven image

mvn package
Maven command

– Jar package is generated in /target folder in host
– As container command is executed as root user
(by default), generated files are owned by root.
– Change to your user
simple-maven-project-with-tests-1.0-SNAPSHOT.jar
sudo chown -R username:group target

•Advantages of dockerized dev tools
– Avoid several developers having different
versions of such tools
– It is very easy to test the same code in different
versions (Java 7, Java 8...)
– Reduce tools configuration problems.You can
compile and execute a project easily
– The same tools can be executed in development
laptops and also in CI environment

•Docker in Continuous Integration
– If you execute dev tools in containers, it is very
easy to compile, test and package in CI
environment
– Only have to execute the same command in
laptop and CI environment
– If a tool changes, only have to change the
command, it is not necessary to install anything
Docker in CI servers

https://jenkins.io/
•Docker in Continuous Integration

● Jenkins installation
– You need Java
– Go to https://jenkins.io/
– Download
– Download LTS Release
– Generic Java Package (.war)

New admin
account
Jenkins installation

● Create new Jenkins job
– Create a job with pipeline
– Pipeline:
● Clone git repository
● Compile, test and package Java project
● Copy test results to Jenkins
Jenkins Job

Creamos una nueva
tarea para descargar el
proyecto y ejecutar los
tests
Jenkins Job

Change command
to execute
dockerized maven
command

node {
// Mark the code checkout 'stage'....
stage 'Checkout'
// Get some code from a GitHub repository
git url: 'https://github.com/jglick/simple-maven-project-with-tests.git'
// Mark the code build 'stage'....
stage 'Build'
// Run the maven build
sh "docker run --rm -v $PWD:/data -w /data maven mvn package"
step([$class: 'JUnitResultArchiver',
testResults: '**/target/surefire-reports/TEST-*.xml'])
}
Pipeline
Jenkins Job

Execute the
new job
Jenkins Job

“Checkout”
stage
Jenkins Job

Compilation and
test stage
Jenkins Job

Successful finished job
build (test passed)
Jenkins Job

Clic on build to see
details
Jenkins Job

See console output
Jenkins Job

Repository clone
and dockerized
maven execution
Jenkins Job

● Advantages of using docker in CI
– CI server just need docker installed, nothing
more
– All tools needed by devs are containerized
– Tools are downloaded (and cached)
automatically when needed
– Several languages/stacks/dependencies can be
used in the same CI server without conflicts
– Sysadmins do not need to give access to CI
server to developers (enforcing security)

● Testing different languages with
Docker
– Testing Node apps with mocha
● https://dzone.com/articles/testing-nodejs-application-
using-mocha-and-docker
– Testing C++ apps with Gtest
● https://github.com/yutakakinjyo/gtest-cmake-example
– Testing Angular apps
● https://jaxenter.com/build-and-test-angular-apps-using
-docker-132371.html

● Some issues of using docker in CI
– Issue: By default project dependencies have to
be downloaded in every build
● Solution: Use a host folder as cache
– Issue: Old docker images waste HD space
● Solution: Use docker garbage collector (as you
can download images when needed)
– Issue: Window tools can’t be dockerized in linux
containers
● Solution: Use portable tools as much as
possible ;)

● Docker plugins for Jenkins
– Docker Plugin
● https://wiki.jenkins-ci.org/display/JENKINS/Docker+Plugin
– Docker build step plugin
● https://wiki.jenkins-ci.org/display/JENKINS/Docker+build+step+plugin
– CloudBees Docker Custom Build Environment Plugin
● https://wiki.jenkins-ci.org/display/JENKINS/CloudBees+Docker+Custom+Buil
d+Environment+Plugin
– Docker Slaves Plugin
● https://wiki.jenkins-ci.org/display/JENKINS/Docker+Slaves+Plugin
– Yet Another Docker Plugin:
● https://wiki.jenkins-ci.org/display/JENKINS/Yet+Another+Docker+Plugin

● Testing tools based on docker
– TestContainers
● Define testing dependencies in your JUnit test
● https://www.testcontainers.org/
– Dockunit
● Test your code in several environments
● https://www.npmjs.com/package/dockunit
– Muchas más...

● Conclusions
– Docker containers are changing the way we
develop, build, test and ship software
– Containers allow developers to use the same dev
tools and execute the project in the same
environment
– Containers ease the configuration and share of CI
servers
– If Continuous Integration is easier to use, more
projects will use it and more test will be executed

Thanks!
Do you have any
question?

Using Docker to build and test in your laptop and Jenkins

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