Continuous Integration

Creating and running a Docker Jenkins image

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In this blog post, I’m going to quickly summarize how to create a Docker Jenkins image and how to make it working. I’m going to demonstrate how to create two images, the first with OpenJDK 8 and the second with Oracle JDK 8 installed. So let’s get started.

The following Dockerfile creates a Docker Jenkins image based on the OpenJDK image. First, it updates existing packages, installs curl, git and nano as a text editor. Next, Maven and Jenkins are downloaded and installed. The only Jenkins plugin that is installed, is the greenball plugin. All other required plugins are easier to install via the Jenkins GUI console as this will also resolve plugin dependencies. Lastly, port 8080 is exposed and Jenkins is run.


FROM openjdk:8
RUN apt-get update -qq && apt-get install -qq curl git nano && apt-get clean
RUN curl -sf -o /opt/apache-maven-bin.tar.gz http://archive.apache.org/dist/maven/maven-3/3.3.9/binaries/apache-maven-3.3.9-bin.tar.gz; \
tar xzf /opt/apache-maven-bin.tar.gz -C /opt/; \
rm /opt/apache-maven-bin.tar.gz; \
ln -s /opt/apache-maven-3.3.9 /opt/maven
ENV MAVEN_HOME /opt/maven
ENV JENKINS_HOME /opt/jenkins
ENV JENKINS_MIRROR http://mirrors.jenkins-ci.org
RUN mkdir -p $JENKINS_HOME
RUN curl -sf -o /opt/jenkins/jenkins.war -L $JENKINS_MIRROR/war/latest/jenkins.war
RUN mkdir -p $JENKINS_HOME/plugins; for plugin in greenballs; \
do curl -sf -o $JENKINS_HOME/plugins/${plugin}.hpi -L $JENKINS_MIRROR/plugins/${plugin}/latest/${plugin}.hpi; done
VOLUME $JENKINS_HOME/data
WORKDIR $JENKINS_HOME
EXPOSE 8080
CMD [ "java", "-jar", "jenkins.war" ]

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Dockerfile

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Creating a Oracle JDK image is a bit more costly. First of all, an Ubuntu image with Oracle JDK has to be created. Launchpad offers a Oracle Java installer which automatically downloads and installs Java.


FROM ubuntu:latest
RUN apt-get update -qq && apt-get install -qq software-properties-common && apt-get clean
RUN \
echo oracle-java8-installer shared/accepted-oracle-license-v1-1 select true | debconf-set-selections && \
add-apt-repository -y ppa:webupd8team/java && \
apt-get update && \
apt-get install -y oracle-java8-installer && \
rm -rf /var/lib/apt/lists/* && \
rm -rf /var/cache/oracle-jdk8-installer

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Dockerfile

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In order to indicate that this image contains Oracle JDK 8, it can be tagged (on github) with version 8. This image is the base image for the following Jenkins image. which exactly looks the same as the one with OpenJDK configured.


FROM renewinkler/ubuntu-oraclejdk:8
RUN apt-get update -qq && apt-get install -qq curl git nano && apt-get clean
RUN curl -sf -o /opt/apache-maven-bin.tar.gz http://archive.apache.org/dist/maven/maven-3/3.3.9/binaries/apache-maven-3.3.9-bin.tar.gz; \
tar xzf /opt/apache-maven-bin.tar.gz -C /opt/; \
rm /opt/apache-maven-bin.tar.gz; \
ln -s /opt/apache-maven-3.3.9 /opt/maven
ENV MAVEN_HOME /opt/maven
ENV JENKINS_HOME /opt/jenkins
ENV JENKINS_MIRROR http://mirrors.jenkins-ci.org
RUN mkdir -p $JENKINS_HOME
RUN curl -sf -o /opt/jenkins/jenkins.war -L $JENKINS_MIRROR/war/latest/jenkins.war
RUN mkdir -p $JENKINS_HOME/plugins; for plugin in greenballs; \
do curl -sf -o $JENKINS_HOME/plugins/${plugin}.hpi -L $JENKINS_MIRROR/plugins/${plugin}/latest/${plugin}.hpi; done
VOLUME $JENKINS_HOME/data
WORKDIR $JENKINS_HOME
EXPOSE 8080
CMD [ "java", "-jar", "jenkins.war" ]

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Dockerfile

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Of course, it would have been possible to configure this image with only one Dockerfile. However, that would have less corresponded to the modular idea. In this way, one is flexible and the base image can be reused.

The most eleagnt way to create Docker images out of dockerfiles is to configure an automated build on Dockerhub. I’m not going in these details here, but I show you how to build the image manually. The docker image can be build

docker build . -t jenkins-oraclejdk

and then run as follows

docker run -itd -p 8080:8080 --name jenkins jenkins-oraclejdk

Next, open a web browser and type in http://192.168.99.100:8080/ Once Jenkins is started, an input will appear to create a first user:

firstuser

Next, Jenkins has to be unlocked.

unlockJenkins.png

In order to this, one have to connect to the docker container and get the initial admin password. The following docker command, let you connect to the container.

docker exec -it jenkins /bin/bash

Navigate to the corresponding folder and open the intialAdminPassword file with nano.

nano intialAdminPassword

Double click the password and press enter to copy the password and leave the editor via Ctrl+X. Exit the container by typing in ‚exit‘ and paste the password to the corresponding input field to unlock Jenkins. That’s all. At last, you have the opportunity to customize Jenkins, e.g. by installing additional plugins.

 

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Groove your Jenkins

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Jenkins jobs are part of the infrastructure and shall be considered as a code according to the paradigm of „Infrastructure as Code“. Jenkins allows to create build jobs with Groovy Job DSL. Jobs are no longer created manually through the graphical console, but code is written and checked in. The configuration of the jobs with the whole history can be seen in the version management. In this blog post I want to briefly show how this works in order to facilitate the entry .

A so-called seed job has to be created. If this job is built, a build job is generated from the the seed job which can be run to build the project as usual. Unfortunately, the build job is not automatically updated if the seed job is changed and rerun.

First you need the Job DSL Plugin. The plugin allows to describe build jobs in a Groovy script. Next, a freestyle project is created that will be the seed job. In the configuration you can leave everything empty. In the section Build click the Add build step and then select Process Job DSLs.
process_job_dsl

Then select Use the provided DSL script. The code for the job can directly typed in to the console as shown in the picture below. When selecting Look on Filesystem instead, you have the opportunity to load job DSL scripts from the workspace. This is the recommended option because the scripts can be checked in and managed in the version control.

dsl_config

Before the JDK and Mavenversion can be set in the DSL script, they must first be configured in the settings under Global Configuration Tools.

 

Funny Jenkins Plugins

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There are some funny Jenkins plugins that can spice up a little the builds . In addition, they can even increase the motivation to have good builds. high time to mention them briefly here.

The first plugin is probably the best known . It is the Chuck Norris plugin . When enabled, on every build page Build Chuck Norris appears with one of his saying and keeps things more fun.chuck_wisdom

chuck_norris

The second plugin is the Emotional Jenkins plugin . When a build fails, Jenkins gets visibly upset. Depending on the build state, one of the Jenkins below is displayed on the build page. If the build is successful, Jenkins is satisfied . If a test fails, Jenkins looks a bit sadly . And if there is a compilation error , then Jenkins is angry.

emotional_jenkins

The third plugin is the Continuous Integration Game. Points are gained for fixing broken builds, writing new unit tests, fixing static analysis violation errors etc. On the other side points are loosed for braking the build or producing new testing errors. On Jenkins home, a leaderboard with the current ranking is displayed. The plugin is intended to stimulate a kind of competition among developers, and thus lead to a good build quality.leaderboard

build_points
The last plugin that I want to mention here is the Claim plugin . If a build fails, someone can claim it. The bad build is then assigned to the the appropriate person and all are informed that someone takes care of the build. Not just funny, but even useful.

claim_build

claim_report

Once the plugins are installed, they have to be enabled on per-job basis. To enable the plugins for a specific job, go to the job configuration page, click Add post-build action and select the corresponding feature from the list.

activate_plugins