Introduction

Welcome to the DevOps Library! This is Samantha, and in this lesson, we're going to cover one of our all-time favorite Jenkins add-ons, Jenkins Job Builder. Up until now, you've probably been setting up each of your jobs by hand through the Jenkins Web UI. While that does work for a while, after a dozen jobs or so it starts to become pretty tedious and error prone.

Additionally, there’s also a good chance that none of your Jenkins configuration is version controlled, but all of that's about to change!

Jenkins Job Builder, or JJB for short, uses simple human readable YAML or JSON files to generate Jenkins jobs. This has several advantages; Jenkins configuration stored as code, auditable version controlled jobs, and reusable job templates and macros. It's also very easy to use!

Getting Started

Alright, let’s go ahead and get started with Jenkins Job builder! First, pull up the JJB documentation at the URL below.

http://docs.openstack.org/infra/jenkins-job-builder/

You might be wondering why we're going to Openstack.org for Jenkins docs.
The reason is because Jenkins Job builder was actually created as part of Openstack. Don't worry, you don't need to actually know anything about Openstack, we just wanted to give you a little background information! :)

Installation

Alright, in this lesson we're going to install JJB directly on our Jenkins master, but you can easily run it remotely if you'd prefer. Let's go ahead and SSH into our master. If you're using Ubuntu, you may be tempted to just install JJB using apt-get. Don't do it! If you do, you'll be stuck on an ancient version that doesn't work very well. Instead, let's install it using Pip!

First, run:

apt-get install python-pip

Once pip finishes installing, type:

pip install jenkins-job-builder

Configuration

There we go, that's it for the installation! We're now ready to set up our jenkins_jobs.ini file. We do have a template that you can use, just copy everything we have here to /etc/jenkins_jobs/jenkins_jobs.ini.

[jenkins]
user=admin
password=f73692e127531ecf26df9f1432701415
url=http://127.0.0.1:8080
query_plugins_info=False

Note, you WILL need to change the password to the API token for your Jenkins admin account. To find it, visit the URL to your Jenkins web interface:

http://jenkinsMasterURL/me/configure

You don’t have to have the query plugins info = false line, but it does speed JJB up a bit.

Creating a Job

Alright, we're finally ready to create our first job! Make a "jobs" directory, then create a new yaml file within that folder. We'll name ours test.yaml.

We've prepared a little sample for you to use, you can download it below or just type it exactly as it appears here. If you're not familiar with YAML, it's very picky, so make sure you don't miss anything!

- job:
    name: test_job
    description: 'Automatically generated test'
    project-type: freestyle
    builders:
      - shell: 'ls'

Let’s go through the file a bit so that it makes sense. First, you’ll notice we start out with - job. If you’re familiar with YAML, you’ll know this means we’re creating a job as part of an array. That’s because Jenkins Job builder actually merges all of your YAML files together, so even though we’ll end up with a bunch of individual jobs, they’re all actually part of one big array fed into JJB.

That also means you can have one giant YAML file with every job, template, and configuration, or you can break it apart into individual YAML files to stay organized.

Alright, back to this job. We’re setting a name, description, the project type to freestyle, and we’re even configuring a build step to run a shell command. Let’s go ahead and save the file. Now make sure you're in the parent directory of the jobs folder, then run:

jenkins-jobs update jobs

It should finish almost immediately, once it does, switch to the Jenkins Web UI and refresh the page. Perfect! There we go! Let's take a look at the job configuration. See? We just created a brand new job without ever even needing to use the web interface.

On top of that, we can easily store our job YAML configuration files in a git repository or some other form of source control. We can even do some inception level stuff and have a Jenkins job that runs Jenkins Job builder anytime someone commits to the repository, thus having Jenkins manage Jenkins.

JJB Defaults

Well, we're probably getting a little ahead of ourselves, we haven't even learned how to set defaults for our jobs yet! If you're like most Jenkins users, you've probably noticed that many of your jobs have things in common with each other. That's what defaults are for.

If you set up a "default" configuration named global, it will automatically be applied to any of our Jenkins jobs unless we specifically say not to use it.

Let's go ahead and create another yaml file in our jobs folder. We’ll name it defaults.yaml. For now, feel free to copy everything we have here, unless you know what settings you'd like to use.

- defaults:
    name: global
    logrotate:
      daysToKeep: 30
      numToKeep: 5
      artifactDaysToKeep: -1
      artifactNumToKeep: -1

This configuration tells Jenkins that by default, we only want our jobs to keep our last five builds, for a maximum of 30 days, and that we’d like to save all artifacts indefinitely.

Go ahead and save the file, then rerun Jenkins-jobs update jobs.
Now refresh the Web UI. See? Pretty cool huh!

Templating

Alright, it's finally time to learn about templates! Templates are sort of like the defaults file we just created, in that they allow us to reuse parts of our configuration. But they're a lot more flexible, especially once you understand how to use template variables.

Let's try it out. Reopen our test.yaml file, we’ll convert it into a template. Change "job" to "job-template". We’ll also change the name from test_job to {name}_job. Lastly, let’s replace the shell command from ls to {command}.

- job-template:
    name: '{name}_job'
    description: 'Automatically generated test'
    project-type: freestyle
    builders:
      - shell: '{command}'

Save and close the file.

Now run:

jenkins-jobs update --delete-old jobs

The delete old switch tells JJB to remove any jobs that were previously managed by Jenkins Job builder that shouldn't exist anymore. Because our job is now a job template, JJB deleted it from our Jenkins master. Don't worry, we wanted to do that!

We're now going to take our template that we just created, and use it to create a bunch of different jobs. To do so, we have to create a "project". A JJB project is used to collect related jobs together, and lets us provide values for template variables.

Projects

Let’s make another yaml file, we'll name this one projects.yaml. For the configuration, just give the project a name, then we'll define an array of jobs.
Let's create two, both of them using the {name}_job template that we just created.

Next, if you remember, we defined two variables within our template, name and command. We now need to define those values. Feel free to use whatever you'd like. For our example, we'll make the first job retrieve free disk space, and the second one will list everything under /etc.

That's it! Save the file, then rerun our JJB update command. Now let's look one final time at Jenkins!

Great job!! We now have two brand new jobs, both created from the same template. There's a ton more you can do with Jenkins Job builder, but you're off to a great start!

Conclusion

As always thanks for watching, and a special thanks goes to Hired for sponsoring this course. If you're into DevOps, there's a pretty good chance you've had to deal with pushy recruiters and countless emails, as well as spent many hours on your own searching for good DevOps opportunities.

The reason we love using Hired is because it completely reverses this situation and puts the power back in your hands, by having companies send you interview requests that you can choose to pursue. (They even come with upfront salary and equity!)

By having you fill out information that is specific to what you’re looking for and what you feel your individual strengths and talents are, it ensures that the only companies you'll hear from will be a great fit for you. Plus, Hired is completely free for you, and they’ll even give you a $2,000 bonus after you land a job, using the DevOps library link!

We highly recommend giving them a shot, they really do a fantastic job, especially for the DevOps community.

Thanks again for watching today! If you like our videos, please subscribe to our YouTube channel! If you love them and want to help support us, visit patreon.com/devopslibrary, we’ll even list you on our high scores at the end of each video. Thanks again, see you again soon!