“Continuous Integration doesn’t get rid of bugs, but it does make them dramatically easier to find and remove” M. Fowler Jenkins and Docker are cool technologies. Here's how they serve in a continuous integration based process and how they could be exploited to deliver new version of the same software. The slides present the whole process along with real code snippets.

1. CI with Docker and
Jenkins
Francesco Bruni
Club degli sviluppatori - Bari, May ‘19
@brunifrancesco

2. Who am I
•MSc Telecommunication Engineer @ Poliba
•Despite a Java background, I prefer Python whenever
possible
•I'm not a computer scientist

3. Continuous Integration
•Keep integrating multiple times a day the central code
repository;
•Run as more tests as you can to ensure nothing broke
down;
•Be ready to replicate environment.

4. Why CI matters
•Continuous testing/building for all teammates;
•Let someone do trivial jobs.

5. CI advantage
“Continuous Integration doesn’t get rid
of bugs, but it does make them
dramatically easier to find and remove”
M. Fowler

6. CI requirements
•Single source repo;
•Automated building;
•Self testing build;
•Build fast;
•Run tests in a production env clone;
•Automate deployment.

7. CI cycle
Develop Feature
Integrate in the
main code base
Test/build/label
Checkout code
Correct detected
iussues

8. CI and TDD
TDD
CI

9. CI cycle
•Integrating code should be automated;
•Multiple levels testing;
•Devs must not checkout bugged code;
•Devs must not deploy untested code;

10. CI drawbacks
•Setting files;
•Setting all the stuff up requires time and patience.

11. CI natural evolution:
Continuous Delivery
•If a commit builds (all tests succeed), deliver it;
•Keep delivery time at minimum;
•Multiple deliveries for multiple versions.

12. Know your tools
•Test everything;
•Keep your sources/setting files versioned;
•Containerize everything;
•Automate as much as you can.

13. Test everything
•Test your sources, checking coverage;
•Test for writing new features;
•Test your application settings;
•If you want to deliver software, check external
requirements.

14. Smarter use of VCs
•Keep code versioned: application settings/sources/dep
indexes;
•Keep env settings versioned: scripts and configuration
files;
•Enjoy version control well defined ‘flows’ :)

15. Be containerized
•Develop solutions in well separated envs;
•Ship software as main part of env;
•Don’t play with global deps.
•‘Restore’ basic envs to speed up env creation process.

16. What’s Docker
•Wrap many services in many
containers;
•Create, play with and destroy
containers;
•Save and easily replicate
isolated containers.

17. Dockerfiles
# pull base image.
FROM java:8
# maintainer details
MAINTAINER Francesco Bruni "francesco.bruni@stasbranger.com"
# update packages and install maven
RUN
export DEBIAN_FRONTEND=noninteractive &&
sed -i 's/# (.*multiverse$)/1/g' /etc/apt/sources.list &&
apt-get update &&
apt-get -y upgrade &&
apt-get install -y vim wget curl git maven ssh nano python-pip
# attach volumes
VOLUME /volume/git
# create working directory and set some stuff up
RUN mkdir -p /local/git
WORKDIR /local/git
RUN mkdir -p /root/.ssh
ADD id_rsa /root/.ssh/id_rsa
RUN chmod 700 /root/.ssh/id_rsa
RUN echo "Host <ip>ntStrictHostKeyChecking non" >> /root/.ssh/config
COPY .m2 /root/.m2
COPY run.sh run.sh
RUN chmod a+x run.sh
# run this when container starts
CMD ["./run.sh"]

18. Automate procedures
•Repetitive tasks should be performed by automated
agents;
•Once you teach the agent what to do, it’s up to him to
fulfill the job.

19. What’s Jenkins
•Automated procedures worker;
•Run tasks, report final status,
log activities;
•Multiple plugin for multiple
features;
•Use it just for playing too :)

20. Deploy w/ Docker w/o
Jenkins
•Test code (or at least run a set of tests);
•Push code to repo;
•SSH in the server, enter in container;
•Pull changes and restart required services.
•Check if it works! :)

21. Practical session
•Integrate new code into the
main branch;
•Test all the stuff;
•Deploy it :)

22. What we’ll need
•A GIT web hook;
•Set private “credentials”;
•A tool to test configuration settings;
•A container to run the test suite;
•A container to run the new application;
•A pipeline.

23. GIT web hook
• Bind an action (tipically run a script) to GIT events;
• Notify Jenkins new code has been pushed over the
‘develop’ branch.
#! /bin/bash
read oldrev newrev _branch
tail=$(git log -1 --pretty=format:'%h %cn: %s%b' $newrev)
curl http://<ip>:8080/job/QW/build?
token=vH3YKmrRR5KOT4aeAOAV&commitMessage=
$tail&cause=JenkinsDeploy

24. Merge/Test
configurations
import os
main_path = os.path.join("src",
"main","resources","application.properties")
test_path = os.path.join("src",
"test","resources","application.properties")
for element in (main_path, test_path,):
with open(element) as old_main:
data = map(lambda line: line.strip(), old_main.readlines())
data[6] = data[6].replace("192.168.1.75", "mysql")
data[6] = data[6].replace("<myIp>", "mysql")
with open(element, "wb") as new_main:
new_main.write(“n".join(data))
Connection().quick_connect("user", "password", “db_test", "<myIp>")
Connection().quick_connect("user", "password", "db", "mysql")

25. Create the container
to run test suite
Run tests and see if they fails :)

26. Deploy the new
version
• Create the new container and run the new version;
• The new container should replace an existing one.

27. Going on production
No way, do some manual testing and start a new CD
build

28. All togheter
node {
stage 'Stage 1'
sh 'docker run --rm --link mysqlC:mysql --name sms-checklink-container
sms-checklink'
stage 'Stage 2'
sh 'docker rm -f sms-test-container || echo 'no container to delete''
sh 'docker run --rm --name sms-test-container --link mysqlC:mysql sms-
test'
stage 'Stage 3'
sh 'docker run --rm --name sms-merge-container sms-merge'
stage 'Stage 4'
sh 'docker rm -f sms-staging-container || echo 'no container to delete''
sh 'docker run -d -p 8433:8080 --name sms-staging-container --link
mysqlC:mysql sms-staging'
}

29. Conclusions
• Improve configuration settings handling;
• Reduce testing time;
• Bind Jenkins job to commit messages;
• Improve git-flow integration;
• Docker Compose :(
• Deploy project on production via manual tests.

30. References
Continuous Delivery
Reliable Software Releases through Build, Test,
and Deployment Automation
by Jez Humble and David Farley
Continuous Integration
by Martin Fowler
http://martinfowler.com/articles/continuousIntegration.html

31. References
Docker for beginners
https://scotch.io/tutorials/getting-started-with-docker
Meet Jenkins
https://wiki.jenkins-ci.org/display/JENKINS/Meet+Jenkins
Docker Explained: Using Dockerfiles to Automate
Building of Images
https://www.digitalocean.com/community/tutorials/
docker-explained-using-dockerfiles-to-automate-
building-of-images

32. Let’s see it @ work

33. Questions?
@brunifrancesco