What is CI/CD pipeline?

As previously stated, the CI/CD pipeline incorporates both continuous integration and continuous delivery to create a more-encompassing software development culture and set of operating principles. But what exactly are CI and CD, and how do they relate to continuous deployment?

Continuous Integration (CI) is an approach in which development teams regularly implement and test incremental changes to the code. These changes are then merged to a shared, central repository. The repository is version controlled, allowing developers to view updates and go back to earlier versions when necessary. These iterations, called ‘check ins’ can occur multiple times per day during the development cycle. Every change is verified by an automated build and tests to ensure that issues in the code may be quickly identified and resolved.

While CI automates development and testing, Continuous Delivery (CD) closes the cycle, by automating aspects of software delivery. As feedback is addressed and fixes are implemented, these changes are automatically uploaded until the team makes the decision to push the application to production. CD results in a deployable product but depends on human authorisation to roll out products, allowing teams to decide what should be released and when. This enables developers to continue to refine the application before handing it over to the end user.

Continuous deployment is similar to continuous delivery, so much so that they are sometimes used interchangeably and represented by the same abbreviation (CD). The major difference between continuous deployment is in who actually deploys the software. Instead of requiring human authorisation to release a product, continuous deployment sends every change through an automated pipeline to create a working version, which is then pushed immediately into production. There is no holding for a manual approval cycle, which means that the code itself must be sufficiently tested prior to entering production.

Both CI and CD are essential to modern DevOps, and help support Agile methodologies. As such, an effective CI/CD pipeline brings with it several advantages:

• Clearer processes
  The systematic CI/CD approach clearly lays out each step within the pipeline, providing a detailed overview of exactly what needs to be done to guide a project from conception through to completion.
• Higher-quality code
  Small, incremental changes are easier to review for quality and effectiveness. Likewise, any problems in the code are much more apparent, and can be resolved earlier in the process. This means better code throughout the project.
• Easy access
  With changes automatically stored in a central repository, stakeholders, QA and other authorised teams and individuals have direct access to every version of the product, including the most up-to-date release.
• Reliable version control
  In the event that an issue with the code cannot be easily resolved, rolling back to an earlier version may be necessary. Effective version control practices ensure that this can be done with a minimum of hassle.
• Faster feedback
  A CI/CD pipeline allows users and testers to provide almost immediate feedback, and for development teams to act on that feedback just as quickly.
• Shorter testing cycles
  In traditional development, entire products’ worth of code would have to be tested together again and again, leading to lengthy, complex testing cycles. With smaller volumes of code introduced incrementally in a CI/CD pipeline, this is no longer an issue.
• Improved development agility
  CI/CD pipelines make it possible for development teams to respond instantaneously to the needs of their organisation, and to pivot ongoing projects when necessary. With improved development responsiveness, companies gain the benefits of powerful, specialised software solutions exactly when they need them.