Continuous Integration Interview Questions

So, are you preparing for continuous integration interviews and looking for frequently asked continuous integration interview questions? Well, you have landed at the right place. It can be overwhelming to find many continuous integration interview questions online but going through all of them can be very time-consuming. In this blog, I will talk about the popular 15 continuous integration interview questions that you must know in order to crack your continuous integration interviews with ease. We will be looking at the interview questions which a typical DevOps engineer faces in an interview. This is both for people who are new to the DevOps world and people who are experienced in other fields like Linux or production support and are willing or wanting to move to DevOps. So, let us get started!

Q1. What is continuous integration?

In software development, there are multiple developers or teams who work on different segments of the same web application. So in such cases, you need to execute integration testing by integrating all the developed modules. And in order to do that, an automated process for each piece of code is performed on a daily basis so that all your code gets tested. This process is known as continuous integration.

Continuous integration is defined based on the commit that you are doing. So, every commit that you do to a repository or every change that you do has to be immediately compiled and built and integrated, so that’s called continuous integration.

Q2. How is continuous integration achieved?

• In the first step, all the developers commit their source code changes to the shared git repository.
• In the next step, the Jenkins server checks the shared git repository at specified intervals, and detected changes are then taken into the build.
• Next, the build results and test results are shared with the respective developers, then the build of the application is displayed on a test server like selenium, and automated tests are executed.
• Finally, the clean and tested build is deployed to the production server.

Q3. What are the benefits of continuous integration?

Below are the benefits of continuous integration:

• Reduce integration problems allowing you to deliver software more rapidly
• Fast feedback loop
• Increase transparency and visibility
• Detect and fix issues early
• Improve quality and testability
• Frequent code check-in pushes developers to create modular, less complex code
• Automate the build
• Enforces discipline of frequent automated testing

Q4. Explain the master/slave architecture of Jenkins.

The way that Jenkins is set up is that the Jenkins master will pull code from your remote git repository such as GitHub, and we will check that repository every time there is a code commit. It will distribute the workload of that code, and the tests that need to be applied are code to all of the Jenkins slaves, and then on request, the Jenkins masters and slave will carry out all the builds and tests to be able to produce test reports

Q5. What is a Jenkinsfile?

A Jenkinsfile is a text file that has a definition of the Jenkins pipeline and is checked into a source code repository. This allows for three distinct things to happen, it allows for a code review and iteration of the pipeline, it permits an audit trail for that pipeline and also provides a single source of truth for the pipeline which can be viewed and edited.

Q6. List the continuous integration tools you know. How is Jenkins better than any of the other CI tools?

There are many other CI tools to use:

• Jenkins
• TeamCity
• Bamboo
• Perforce
• Circle CI
• Go
• ThoughtWorks
• Integrity
• Travis CI

Honestly, we cannot say that Jenkins is better than any other CI tool because each one has its own unique feature. For example, TeamCity offers .NET support pretty well, but it is costly and complex. Travis CI is a free CI tool just like Jenkins and has good documentation. Bamboo also offers faster and efficient builds, but it is not entirely free.

Q7. What do you mean by pipeline as a code?

Pipeline as a code describes a group of features that allow Jenkins users to define pipelined job processes with code stored and versioned in the source code repository. This group of features will enable Jenkins to discover, manage, and run jobs for multiple source repositories and branches, eliminating the need for manual job creation and management. To use the pipeline as a code, projects must contain the file names jenkinsfile in the repository root, which includes a pipeline script. Additionally, one of the enabling jobs needs to be configured in Jenkins. The first one is the multi-branch pipeline, where you build multiple branches of a single repository automatically. And the second is organization folders, here you scan a GitHub organization or bitbucket team to discover an organization’s repositories, automatically creating managed multi-branch pipeline jobs for them.

Q8. What are the differences between continuous delivery, continuous deployment, and continuous integration?

Developers practicing continuous integration merge their code changes back to the main branch as often as possible. By doing so, you avoid the integration blunders that usually happen when people wait for release day to merge their changes into the release branch.

Continuous delivery is an extension of continuous integration, which makes sure that you can release new changes in the production environment which can be made available to your customers quickly in a sustainable way. So, apart from automating the testing of the product, you also have automated the application release process. You can deploy the application at any point in time with a single click of a button.

Continuous deployment goes one step further than continuous delivery. With this practice, every change that passes all the stages of your production pipeline is released to your customers. There is no human intervention in this practice, and only a failed test will prevent a new change from being deployed to production.

Q9. Mention some of the commonly used Jenkins plugins.

• Git Plugin: Git plugin is often used in projects to know whether the codes written are stable or not.
• SSH Plugin: This plugin is used to run shell commands through SSH on a remote machine as they are derived from the SCP plugin.
• Build Pipeline plugin: This plugin provides a build pipeline view of upstream and downstream connected jobs that typically form a build pipeline.
• Email-ext plugin: This plugin allows you to configure every aspect of email notifications. You can customize when an email is sent, who should receive it, and what the email says.
• HTML Publisher plugin: This plugin publishes HTML reports.\
• Multi-slave config plugin: This plugin allows administrators to configure, add and delete several dumb slaves at the same time.
• Parameterized Trigger plugin: This plugin lets you trigger new builds when your build has completed, with various ways of specifying parameters for the new build.

Q10. What are the key concepts and aspects of working with a Jenkins pipeline?

You need to go through four key areas, and that is pipeline, node, step, and stage.

• Pipeline refers to the user-defined model of a continuous delivery pipeline.
• Nodes are the machines that are part of that Jenkins environment within the pipeline.
• Step is a single task that tells Jenkins what to do at that particular point in time.
• Stage defines a conceptually distinct subset of tasks performed through the entire pipeline, and the tasks could be build, test and deploy.

Q11. What are the two components that Jenkins is mainly integrated with?

Jenkins integrates with:

• Build tools/ Build working script like maven script.
• Version control system/Accessible source code repository like Git repository.

Q12. Explain the two types of pipeline used in Jenkins along with the syntax.

There are two types of Jenkins pipeline, scripted and declarative.

A scripted pipeline is based on the groovy script as a domain-specific language for Jenkins. There are one or more node blocks that are used throughout the entire pipeline. For example:

node {
    stage(‘Demo’) {
        if (env.BRANCH_NAME == 'master') {           
echo 'This is a master branch'
        } else {
           
echo 'Other branch'
        }
    }
}

The second type of Jenkins pipeline is a declarative pipeline and a declarative pipeline is simple and has a friendly syntax to define what the pipeline should look like. And then you can actually, at this point, use an example to break out how blocks are used to find the work completed in a declarative pipeline.

pipeline {
    agent { docker { image 'golang' } }
    stages {
        stage('build') {
            steps {
                sh 'go version'
            }
        }
    }
}

Q13. List the security mechanisms in Jenkins to authenticate users.

Security is fundamental to all the work that we do within DevOps, and Jenkins provides the center core to all the work that gets completed within a DevOps environment. There are three ways in which you can apply security to authenticate users effectively:

1. Jenkins has its own internal database to store user data and credentials securely.
2. You can use a LDAP or lightweight directory access protocol server to be able to authenticate Jenkins users.
3. You can actually configure Jenkins using an authentication mechanism such as OAuth, which is a more modern method of authenticating users.

Q14. What are Triggers?

Trigger in Jenkins are used to define the way in which the pipeline should execute frequently. Cron, PollSCM, etc., are few common available Triggers.

Q15. Which SCM tools are supported in Jenkins?

Jenkins supported SCM tools include:

• CVS
• Git
• Subversion
• AccuRev SCM
• Perforce
• Clearcase
• RTC
• Mercurial

Final Thoughts

Continuous integration is an integral part of the DevOps lifecycle, and there is plenty to learn. Do not just mug up these answers, understand the technicalities of these answers also. You can find thousands of continuous integration interview questions online, but these are the top 15 continuous integration interview questions which you must know, and these are the questions that will give you a kickstart to your future continuous integration interviews. So, prepare well and all the best!