Continuous integration with Jenkins - Tutorial
Jenkins
This article describes
how to build a continuous integration cycle for Java development with the
Jenkins continuous integration build server.
Table of Contents
1. Using the Jenkins
build server
2. Installation
2.1.
2.2. Installing of the Jenkins server on Ubuntu
2.3. Using the .WAR file of Jenkins
3. Configure Jenkins
3.1. Configuration the JDK location
3.2. Secure Jenkins
3.3. Generate ssh key for Jenkins user
4. Jenkins management
4.1. Plug-in management
4.2. Restart your Jenkins
5. Support for the Git
version control systems
6. Setting up a Jenkins
job
7. Prerequisites for
build Android apps with Jenkins
8. How to build your
Android application with Jenkins
8.1. Overview
8.2. Android Jenkins build job prerequisites
8.3. Installation of the Android SDK
8.4. Jenkins Plug-ins for installation
8.5. Running an Android build with Jenkins
8.6. Other useful plug-ins
9. Jenkins backup and
copying files
9.1. Jenkins backup and copying files
9.2. Managing Jenkins with Git
10. About this website
1. Using the Jenkins build server
Continuous integration is a process in which all development work
is integrated as early as possible and the resulting artifacts are
automatically created and tested. This process should identify errors as very
early in the process.
Jenkins is one open source tool to perform continuous integration
and build automation. The basic functionality of Jenkins is to execute a
predefined list of steps. The trigger for this execution can be time or event
based. For example every 20 minutes or after a new commit in a Git repository.
The list of steps can, for example, include:
·
perform a software build
with Apache Maven or Gradle
·
Run a shell script
·
Archive the build result
·
Afterwards start the
integration tests
Jenkins also monitors the execution of the steps
and allows to stop the process if one of the steps fails. Jenkins can also send
out notifications about the build success or failure.
Jenkins can be extended by additional plug-ins, e.g., for building
and testing Android applications or to support the Git version control system.
Jenkins can be started via the command line or
can run in a web application server. Under Linux you can also install Jenkins
as a system service.
For most platforms you have native packages, see
the Jenkins
Homepage.
Jenkins provides Debian/Ubuntu packages which
install Jenkins and register Jenkins as start service. See the Install Jenkins on Ubuntu description.
Jenkins stores all the settings, logs and build
artifacts in its home directory. The default installation directory is /var/lib/jenkins under
Ubuntu.
This creates a /etc/init.d/jenkins start script which starts Jenkins automatically at boot
time. If you installed Jenkins locally, you find it running under the following
URL:http://localhost:8080/
You can also start Jenkins directly via the
command line with java -jar jenkins*.war. If you start it locally, you find it running
under the following URL: http://localhost:8080/
To run it in your Tomcat server, put the .WAR
file into the webapps directory. If you start Tomcat, your
Jenkins installation will be available under http://localhost:8080/jenkins
Note
If the jenkins.war is deployed in your webapps directory, but
cannot be started and the tomcat manager says “FAIL - Application at
context path /jenkins could not be started ”, you may need to grant the
permissons for JENKINS_HOME.
cd /usr/share/tomcat7
sudo mkdir
.jenkins
sudo
chown
tomcat7:nogroup .jenkins
This makes the .jenkins folder writable and
Jenkins can use it.
3. Configure Jenkins
Before using Jenkins to build Java applications,
you need to configure the location or it where your JDK installation is. Select Manage
Jenkins and afterwards Configure System.
Enter the correct path to your JDK, Apache Ant
and Maven and press the Savebutton below. Jenkins can also install these
for your automatically.
It is recommended to secure Jenkins. Manage
Jenkins and then Configure Global Security. Select the Enable
security flag. The easiest way is to use Jenkins own user database. Create
at least the user "Anonymous" with read access. Also create entries
for the users you want to add in the next step.
On the login page, select Create an account to
create the users you just gave access.
Go to Manage Jenkins, Manage and
Assign Roles and then Assign Roles to grant the newly created
user additional access rights.
Navigate to Manage Roles to define
access restrictions in detail. Pattern is a regex value of the job
name. The following grants unregistered users read-only access to your build
jobs that start with the C-MASTER or M-MASTER prefix and only
those.
If you want to access a private Git repo, for
example at Github, you need to generate an ssh key-pair. Create a SSH key with
the following command: sudo -u
jenkins ssh-keygen.
Jenkins can be extended via additional plug-ins
with more functionality. You can configure your plug-ins via the Manage
Jenkins → Manager Plugins link.
To install plugins in Jenkins select use the Manage
Jenkins → Manager Pluginslink and search for the plugin you want to
install. Select it from the list and select to install it and restart Jenkins.
The following table is a summary of commonly
used plug-ins.
Table 1. Jenkins plug-ins
|
Plug-in name
|
Description
|
URL
|
|
Git Plugin
|
This plugin allows use of Git as a
build SCM.
|
https://wiki.jenkins-ci.org/display/JENKINS/Git+Plugin
|
|
Xvnc plugin
|
This plugin allows projects to run
xvnc during a build.
This allows for example to run tests which requires a
display to run on a virtual display. To use this plug-in you need to connect
once to your vncserver on the command line to provide a password. Use for
example the following commands.
# install vncserver
apt-get install vnc4server
# switch to jenkins user
sudo su jenkins
# connect to vncserver which creates the password
vncserver :10
|
wiki.jenkins-ci.org/display/JENKINS/Xvnc+Plugin
|
|
Gradle Plugin
|
This plugin allows to run Gradle
builds, e.g., as required for Android, via Jenkins.
|
https://wiki.jenkins-ci.org/display/JENKINS/Gradle+Plugin
|
|
Maven Plugin
|
This plugin allows to run Maven
builds.
|
https://wiki.jenkins-ci.org/display/JENKINS/Maven+Project+Plugin
|
|
GitHub plugin
|
This plugin integrates Jenkins
with Github projects.
|
https://wiki.jenkins-ci.org/display/JENKINS/Github+Plugin
|
|
Publish Over SSH Plugin
|
This plugin allows to publish
build artifacts via ssh
|
https://wiki.jenkins-ci.org/display/JENKINS/Publish+Over+SSH+Plugin
|
|
Workspace Cleanup Plugin
|
This plugin allows to delete the
workspace before the build or when a build is finished and artifacts saved.
|
https://wiki.jenkins-ci.org/display/JENKINS/Workspace+Cleanup+Plugin
|
|
Github Pull Request Builder
|
This plugin allows to build Github
Pull Requests
|
https://wiki.jenkins-ci.org/display/JENKINS/GitHub+pull+request+builder+plugin
|
You can manually restart Jenkins by adding restart as URL parameter.
5. Support for the Git version control
systems
Jenkins supports the Git version control system
via a plugin. Select the Manage Jenkins → Manager Plugins link.
Here you have to install the Git Plugin.
To clone a Git repostory via Jenkins you need to
enter the email and user name for your Jenkins system. For this switch into
your job directory and run the git
config command.
# Need to configure the Git email and user for the Jenkins job
# switch to the job directory
cd /var/lib/jenkins/jobs/Android/workspace
# setup name and email
sudo git config user.name "jenkins"
sudo git config user.email "prakash@gmail.com"
The build of a project is handled via jobs in
Jenkins. Select New Item from the menu
Afterwards enter a name for the job and select Freestyle
Job. Press OK to create a new Job in Jenkins.
The next page allows you to configure your job.
If you for example using Git, enter the URL to the Git repository. If the
repository is not public, you may also need to configure the credentials.
Specify when and how your build should be
triggered. The following example polls the Git repository every 15 min and
triggers a build, if something has changed in the repo.
I typically delete the workspace before a build
to avoid any side-effect. In the Build section you can add a build step, e.g.,
a Maven build.
Press Save to finish the job
definition. Press Build Now on the job page to validate the job works
as expected.
After a while the job should go to green or blue
(depending on your configuration), if successful. Click on the job and
afterwards on Console Output to see the log file in case of an error
or to validate that log looks as expected.
The following descriptions for build Android
applications with Jenkins assume that you have already a correct Gradle build
file for your Android application. See Android build tutorial.
Jenkins supports the automatic building and
testing of Android applications.
To create a build job on Jenkins you need to
have a working build setup. The Android tooling generates automatically a valid
Gradle build file.
The Android SDk must be available on the server.
If you build server has no display server you need to install the Android SDK
from the command line. You also need to configure the location for the Android
SKD for Jenkins.
# download the Android SDK via wget
# for the correct URL see http://developer.android.com/sdk/index.html
# and look in the section "SDK
Tools Only"
wget <link from the above website>
# example
# wget http://dl.google.com/android/android-sdk_r24.2-linux.tgz
# unpack it
tar zxvf filename
# Add the new directory to your patch
# assumes you exported it to /opt/
# this must be set for the Jenkins user
export ANDROID_HOME="/opt/android-sdk-linux"
export PATH="$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools:$PATH"
// run this as Jenkins user
android update sdk --no-ui
Use android
list targets to see what ABIs
are installed. If no are listed manual install one.
You need the follwing plug-ins to build Android
application with Jenkins:
·
Gradle Plugin
·
Git Plugin - if Git is
used for the project sources
·
Android Emulator Plugin
- supporting starting and unlocking an Android emulator and blocks the build
until the emulator has started. Required for running tests. A detailed
description of this plugin can be found under the following URL: Android Emulator Plugin Jenkins page.
To create an Android build job on Jenkins,
select New Job, enter a job name and select theBuild a free-style software
project option.
You configure from where the source should be
cloned.
You configure the emulator which should be
started. Ensure that you do not select the Show emulator window option,
as your build server should not depend on the availability of a display server.
Add a Gradle build step to your Jenkins jobs.
The Android Emulator Plugin supports
a new job with the Build multi-configuration projectoption. This option
allows you to test multiple emulator configurations at the same time. You can,
for example, test different languages, densities, screen resolutions, etc.
Typically you have two Jobs, one for a simple build and test run and a
multi-configuration project to test the build on different device
configurations.
You can combine Android Emulator Plugin with
the Amazon-EC2-Plug-in to run the build and theJenk tests on
several machines simultaneously.
Another useful plug-in is the Lint plug-in which
allows to run your Lint checks via Jenkins. See Lint Plug-in for details.
9.1. Jenkins backup and copying files
Jenkins stores all the settings, logs and build
artifacts in its home directory, for example, in/var/lib/jenkins under
the default install location of Ubuntu.
To create a backup of your Jenkins setup, just
copy this directory.
The jobs directory contains the individual jobs
configured in the Jenkins install. You can move a job from one Jenkins
installation to another by copying the corresponding job directory. You can
also copy a job directory to clone a job or rename the directory.
Click reload config button in the
Jenkins web user interface to force Jenkins to reload configuration from the
disk.
See Adminstration of Jenkins for details.
Jenkins supports the https://wiki.jenkins-ci.org/display/JENKINS/SCM+Sync+configuration+plugin
plug-in which allows you to store every change in a Git repo.
It is also possible to manually maintain the
Jenkins configuration in a Git repo.
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