CI/CD: What Is It & Why Is It Important for DevOps?

“Merge conflict” is one of the worst messages you can see in Git as a developer. You've spent hours working on a feature and finally have your code perfect. But someone else has changed the same part of the file, so now you need to compare the differences, choose which edits to keep, and run all your tests again before trying to merge a second time.

If a merge conflict occurs once in a while, it's a minor nuisance. But imagine you're working on a highly integrated team that's trying to push out new features at rapid speed. The timeline means that multiple developers need to work in the same file. If everyone waits until their individual contributions are finished to push to the repository, merge conflicts abound. This type of error is not only frustrating, but inefficient.

The CI/CD approach was created to solve this problem and streamline development. Let’s take a look at what this approach is, why it’s important, and what tools you can use to implement it.

What is CI/CD?

CI/CD is a strategy to automate the development process to speed up turnaround time. CI, or continuous integration, is the practice of frequently merging code changes into a shared branch. CD can refer to continuous delivery or deployment, which both automate the release and rollout of the application after merging.

CI/CD's purpose is to build a pipeline that integrates code edits from individual developers into a shared branch, tests the updates against requirements in a demo environment, packages the validated code into a shared repository, and automatically deploys the new software version.

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CI/CD is typically practiced by agile development and operations teams following either a DevOps or site reliability engineering (SRE) approach. CI streamlines the coding and build processes for the development team, whereas CD streamlines the release and deployment processes for the operations team.

Let's examine each component of the CI/CD method.

Continuous Integration

Continuous integration (CI) is an automation strategy meant to solve the challenges of merge conflicts between individual developers' code and separate code branches. CI introduces workflows to frequently compile code changes, build the application, and test the new version for bugs and errors. If it passes the testing suite, the updates are cleared for the next phase of the development process.

In agile methodology, developers are working together to divide the workload and create features faster. However, the more changes made, the higher the chances one edit will conflict with another.

CI works to address this issue by frequently merging changes in a shared branch, sometimes referred to as a trunk branch. This strategy lowers the chance of merge conflicts versus waiting until the end of the coding phase to attempt to integrate separate branches, and any issues that do occur will be less complex and easier to resolve.

Once code changes are merged, the application is built in a demo environment, and automated tests are run against it. This ensures that edits are constantly being validated and lessens the risk of bugs making it to the delivery and deployment phase. Evaluations will range from unit tests of individual files to integration tests of the larger app infrastructure. If bugs are discovered, developers can address them quickly before more code is written on top of a defective code base.

Organizations typically start building their CI/CD pipelines by focusing on the CI component. Once they have automated the merge process, they move on to continuous delivery.

Continuous Delivery

Continuous delivery is the next evolution in the automation of the software lifecycle. Once code has been bug tested, it is immediately released to a shared repository like GitHub. Continuous delivery is intended to improve visibility and communication between the development and operations teams by speeding the rate at which production-ready code is delivered. The operations team can then deploy the application with ease.

Continuous delivery is only effective when CI is also implemented. Testing in the CI phase is critical to validate that code is ready for release to the repository. Otherwise, defective code is automatically delivered, leaving bugs that are then pushed to production.

Organizations that have implemented CI and continuous delivery are now ready for the final evolution of the CI/CD pipeline: continuous deployment.

Continuous Deployment

Continuous deployment takes the benefits of continuous delivery a step further: now, the code is automatically pushed to a repository and then deployed to production in the same process. This relieves a potential burden on the operations team to manually deploy new releases, which may be numerous depending on the pace of the development team.

However, automating manual deployment processes places an even greater emphasis on effective test automation during the CI phase because this is now the main failsafe before bugs are pushed to production.

With effective test design, continuous deployment streamlines the software development lifecycle. Now, a developer can make changes to a feature, and — assuming they clear the testing phase — those changes can go live in minutes. This creates an effective feedback loop where customers can raise issues and the development team can quickly address them.

Continuous deployment also enables simpler updates where small changes are released incrementally versus in one large batch, aligning with the agile methodology. The lower complexity of these updates means a lower risk of defects and issues.

This video by Stephane Maarek reviews the components of CI/CD and their differences:

Now that you understand the individual pieces of CI/CD, let's review why it matters in the world of software development.

Why is CI/CD important?

CI/CD automates the process of integrating, releasing, and deploying software while removing traditional roadblocks. It supports the larger goal of agile methodology to accelerate the software development lifecycle, and it supports the DevOps approach of aligning development and operations teams.

In addition to supporting these larger goals, CI/CD enables you to:

• Ship software quickly and efficiently: CI/CD pipelines move applications from the coding to deployment phases at scale, ensuring that the pace of development matches the needs of the business.
• Increase productivity: By implementing automated processes, development and operations teams are no longer spending time merging, building, testing, releasing, and deploying software manually. Instead, they can focus on writing better code and monitoring deployments for issues.
• Reduce risk on delivery: Testing every change before it's deployed ensures that the result will be a higher quality product and lower the rate of bugs in production. Customers will receive a better product, and the development team will spend less time fixing urgent defects discovered after release.
• Incorporate user feedback faster: CI/CD removes traditional roadblocks for development and operations teams, enabling the faster release of new features to meet users' needs. This will increase customer satisfaction and provide valuable insights into the capabilities that users value for future projects.
• Standardize processes: Automating the merge, test, delivery, and deployment processes means that they will always follow the same structure. This standardizes the pipeline, whereas manual execution of these tasks always comes with the risk of human error, such as executing tests in a different order.

Now that you understand the importance of CI/CD for speeding development and improving the end product, let's examine the CI/CD pipeline.

What is a CI/CD pipeline?

The CI/CD pipeline is the CI/CD philosophy in practice. The pipeline represents the combination of strategies, people, and tools that achieve a CI/CD approach to software development. They usually form part of a larger DevOps pipeline and are considered a best practice for DevOps teams.

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This video by Edureka reviews the definition of CI/CD and then walks through how to create a CI/CD pipeline using Jenkins:

To build an effective CI/CD pipeline, you need the right tools.

CI/CD Tools

As with most automation strategies, CI/CD relies on tools to achieve optimal workflows. Below is a selection of tools purpose-built to orchestrate CI/CD pipelines.

Let's review each one.

1. Jenkins

Price: Free

Jenkins is an automation server built to create a CI/CD environment for almost any combination of languages and repositories. It offers robust functionalities to incorporate individual build, test, release, and deployment tools and connect these into one pipeline using scripts to orchestrate the individual steps. Jenkins is open source and has more than 1,600 plugins, allowing users to automate development tasks beyond the CI/CD pipeline.

2. CircleCI

Price: Free with paid plans available

CircleCI is a CI/CD automation platform built with an emphasis on speed. It offers change validation to ensure every edit is tested before it's committed and has universal support for every coding language as well as multiple execution environments. In addition, CircleCI comes in cloud and on-premise configurations and provides installation services plus ongoing support from dedicated engineers to ensure user success.

3. Spinnaker

Price: Free

Spinnaker is an open-source continuous delivery platform that integrates with major cloud providers, including AWS, Google Cloud, Microsoft Azure, and Oracle Cloud. Its powerful and flexible pipeline management system provides integration and system testing as well as oversight for deployments through integration with monitoring tools such as Datadog, Stackdriver, and New Relic.

4. Bamboo Data Center

Price: Free trial with paid plans available

Atlassian's Bamboo Bamboo Data Center is a CI server that focuses on resilience, reliability, and scalability, ensuring that the CI/CD pipeline will always be available with built-in disaster recovery. The platform integrates with the rest of the Atlassian suite of products, including Bitbucket and Jira to support development workflows and Opsgenie to provide incident investigation capabilities for the operations team.

5. Travis CI

Price: Free trial with paid plans available

Travis CI is an automated testing and deployment server that connects with Assembla, Bitbucket, GitHub, or GitLab repositories to test pull requests before they're merged. Builds that pass are automatically deployed. Travis CI offers cost-free testing for open-source projects and supports more than 30 languages, including Java, Node.js, PHP, Ruby, and Python.

In addition to the purpose-built CI/CD tools listed here, any tool that powers a DevOps pipeline will likely make up part of the CI/CD workflow. For example, a version control system like Git will be needed to track developers' changes and maintain branches for merging edits during the CI phase. Find more solutions in this list of DevOps tools.

Supercharge your DevOps team with CI/CD.

CI/CD supports modern development by shortening the time between coding and deployment. It maximizes development and operations teams' time by automating manual steps of the integration, delivery, and deployment processes while reducing bugs through a well-designed testing suite. CI/CD forms the backbone of DevOps and SRE methodologies by enabling the team to match the speed of the business.