Our world is driven by technology, but we seldom think about just how much our individual lives depend on it. Right from waking up with a digital alarm clock to listening to music, from hiring a cab to accessing emails, everything is made possible by the various software applications.
But what is it that gives software this capability to perform so many tasks?
Well, it’s the thousands of lines of code that go into building it!
Now when software developers write code for applications, despite their years of experience, it’s natural for them to make mistakes sometimes (they are, after all, humans). Due to these mistakes, the application might contain bugs or faults which can make it behave unexpectedly, thus preventing the end-users from achieving their desired purpose. They can also eventually make end-users abandon the application altogether. To ensure that doesn’t happen, every application is tested rigorously in dummy environments before it is released to end-users. Software testing can often take days and even weeks, during which the application is subjected to several test scenarios to see how it performs under unpredictable situations.
Quite understandably, manually doing all of this isn’t very productive (even though that was the norm up until a decade ago). Today, automated testing tools and environments make it easy for software developers to test the applications they write, and Jenkins is one such tool that makes the life of developers and testers very easy.
In this post, let’s learn more about Jenkins and its core concepts.
What is Jenkins?
Jenkins is an open-source automation server that lets software developers easily and freely automate different aspects of the software development lifecycle, like building, testing, and deploying. It helps developers continuously integrate (CI) and introduce changes in software after it becomes live, and it can also help in the continuous delivery (CD) of new features. It is used in DevOps along with other cloud-native tools.
Automation in CI/CD is a key aspect that allows DevOps teams to deliver projects faster, cheaper, and better. Due to its automation feature, Jenkins has become an indispensable tool for DevOps teams, and it is widely used by various organizations across the world.
Why taking it up as a career can be beneficial?
As already highlighted, Jenkins has gained widespread popularity among IT organizations and software developers. Quite evidently, this has led to a huge demand for professionals having Jenkins expertise.
According to enlyft research data, over 57,000 companies use Jenkins in the software industry. The actual figure could be much larger due to the high dispensability of the tool. It has a 9.78% market share among all software development tools, and it’s used in diverse industries like computer software, information and technology services, hospital and health care, financial services, Internet, retail, telecommunications, hardware, insurance, marketing, and advertising. The CI/CD tool is popular in countries like the US, UK, India, Canada, Germany, France, Australia, Brazil, Spain, and the Netherlands.
Given its extensive usage across industries and geographies, it’s a no-brainer that when it comes to bagging lucrative jobs, Jenkins could prove to be your golden ticket. Most of the companies that use this tool range in the 1 million to 10 million dollar revenue bracket. Answering “why become a Jenkins developer” question after this should be pretty straightforward.
What are the skills needed to be a Jenkins expert?
First, allow us to set the record straight – there are no such prerequisite skills to learn Jenkins and become an expert. It all depends on your determination and hard work.
Now, if you’re already a part of the DevOps domain, getting hands-on with Jenkins might be a bit easier for you as you’d know the different stages of application development. If you’re not from the software development field and are starting fresh, it would be good to gather knowledge about DevOps first because Jenkins is considered to be a DevOps tool. It’s written in Java and integrates with Java build tools like Apache Ant and Apache Maven.
Now that we’ve covered the basic aspect related to being a Jenkins developer, let’s move on to the part you’re most eager to learn about – the key Jenkins interview questions that can provide you an entry into this domain. Before we start, you should know there can be many more questions that you might be asked in a Jenkins interview, and we recommend conducting further research to learn about as many of them as possible.
Most common Jenkins interview questions with answers
The interview questions are split into two categories – Fresher and Intermediate. Let’s begin with fresher-level questions first. These are aimed at candidates who are just starting in this field.
Fresher level Jenkins interview questions
What are continuous integration, continuous delivery, and continuous deployment in software development?
Continuous integration refers to constantly merging code changes with the master copy of the application code. Thereafter, when a patch is ready, developers move on to the next phases of the software development process.
Continuous delivery refers to the stage where code changes are automatically deployed onto a testing or production environment. A continuous delivery cycle can be established to release builds every day, every week, or any other schedule that fits the requirement. It allows isolating problems to specific builds and makes for better troubleshooting.
Continuous deployment is the super-speed version of continuous delivery. In this process, every code change that clears all quality checks and other parameters is directly released to customers. This is a great way to accelerate the delivery rate to customers, without having to rely on specific “release days”.
What are the most common use cases for Jenkins?
Since Jenkins is an open-source automation tool, it can be applied to any kind of software-based automation. But to name the most common use-cases, it can be used for:
- General-purpose automation
- Software build jobs
- Code coverage measurement jobs
- Sanity/Smoke/CI/Regression test jobs
- Reverse Engineering jobs
- Web/Data Scraping related jobs
- Key Decoding jobs
What are the different ways to install Jenkins?
It can be installed in the following ways:
- Standalone (on any system that has Java Runtime Environment installed)
- Kubernetes. It is available as helm (which is a package manager for Kubernetes) and can be installed on Kubernetes charts
- Docker. It is available in varied Docker images and can be installed on UNIX, Mac, and Windows.
- Native System Package managers like brew (Mac) and apt (Linux)
What are the different types of pipelines in Jenkins?
Jenkins Pipelines are of two types – Declarative and Scripted. In the Declarative pipeline, the developer uses generic, pre-defined code snippets to build jobs according to build or automation needs. On the other hand, a scripted pipeline has custom-defined stages/steps and uses Groovy syntax that offers better control and precise execution levels.
Now, let’s discuss the intermediate-level Jenkins interview questions.
Intermediate level Jenkins interview questions
What are the different ways to trigger a Jenkins pipeline/job?
There are several ways to trigger Jenkins job, like:
- Manually from Jenkins web application
- Through Jenkins CLI from the master/slave nodes
- By using POST API request to the target job URL with data
- Through time-based scheduled triggers like a cron job
- With downstream/upstream triggers from other Jenkins pipelines
- With event-based triggers like WebHooks and SCM Actions like Pull Request and Git Commit
How does the automation tool know when to execute a scheduled job/pipeline and how it is triggered?
Jenkins has master/slave architecture. The Master is a central coordinating process that schedules the jobs, assigns slaves, and sends them to build jobs. The Master will have cron entries for all scheduled jobs. When the time comes for executing the job, it commands slaves to execute it with the required configuration. The command slaves could be containers or machines that connect to Jenkins Master.
What credential types are supported in Jenkins?
Jenkins credentials are managed by a built-in plug-in known as Credentials Binding, which can handle the following credentials:
- Username and password – It can store basic authentication along with information
- Secret file – A secret file to authenticate security handshakes and secure data services
- Secret text – Tokens like JSON token and API token
- SSH username with a private key – can store a pair of SSH users with a private key for the machine-to-machine authentication.
- Certificate – PKCS#12 certificate file and password
- Docker Host Certificate Authentication credentials
It can also handle extended credentials like Azure secrets, AWS credentials by using plugins.
Conclusion
Jenkins is a popular automation tool that has revolutionized the software development industry. It enables DevOps engineers to build, test, and deploy applications faster while improving their function and performance even after they’re live. If you’re interested in making a career in the software development industry, you can learn Jenkins and explore different job opportunities in varied industry verticals. Just make sure you have basic to advanced knowledge of Jenkins concepts and methods to crack the interview.
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