As your organization grows and application and infrastructure complexity increase good DevOps processes become very important to be able to reliably deliver software. In this post we're going to go over continuous integration and continuous delivery and show how they should be a vital part of your DevOps processes, and how CI/CD can enable your team to deliver software reliably and with confidence.
What is continuous integration?
Continuous integration (CI) is the practice of integrating code from multiple developers into a central repository (or branch), multiple times per day. A CI build consists of an automated process that runs tests (unit and integration), code style checks and so on. This automated process helps the developers on your team to be reasonably confident that the changes they pushed have not “broken the build” and enables them to catch problems early on, before they hit staging and well before they hit production.
Some organizations run CI on each git push (to any branch) and some run CI only on open Pull Requests. This decision is left to the reader to decide what strategy would best serve their organization.
Continuous integration enables your team to iterate freely on new features by providing them with an easy mechanism to integrate their changes back into the main branch. This prevents large features from being developed in silos and integrated
only at the very end. Your team should be able to integrate their features, even if incomplete, into the main branch, and test that the changes have not broken anything. One common strategy for integrating unfinished features is using feature flags, where the given feature is not enabled to the end user but can still go through the entire CI process to verify it doesn't impact any existing functionality under the hood.
This allows other team members to be up to date with the coming new features and are able to plan their work accordingly if it somehow impacts them.
What is continuous delivery?
The job of continuous delivery is to make deploying your application an ordinary and unremarkable event that anyone on the team can do. We do this by automating the release and deployment process that keeps the codebase in an always deployable state.
Continuous delivery is a natural extension of continuous integration as it picks up right where the previous step left off. This can mean automating the artifact creation (docker images for instance) and automating the steps required to deploy the application. We call this a pipeline. A pipeline consists of multiple steps; each step has a series of tests to verify if everything is okay and advances to the next or notifies the team about an error.
It's important to note that this impacts each PR (or commit) so that it becomes each developers responsibility to worry about their code being deployable. A shared responsibility like this allows each team member to fully own their feature, from development to CI to production and enables them to iterate quickly without being blocked by a dedicated team (or person) that does deployments.
It's worth noting that continuous deployment takes things a step further by automatically deploying the artifact produced from previous steps directly to production. This is a giant leap that doesn't require a human gatekeeper to decide when is a good time to trigger a deploy manually, rather each change is directly, and automatically, deployed to production.
This requires very rigorous testing to have enough confidence that new changes don't break anything, as well as encouraging developing features in smaller increments. For more information about the right level of quality assurance see here.
Benefits of CI/CD
CI/CD enables your organization to grow your team, codebase, and infrastructure. It removes the fear and anxiety associated with deploying changes to production. By automating the building, testing and deployment phases of your pipeline you remove any form of gate-keeping and make deploying to production a non-event.
It encourages each team member to own their code throughout its entire life-cycle (not just until it's merged into master), as well as small iterative changes rather than huge features that have been brewing a very long time.
Challenges when implementing CI/CD
Implementing CI/CD is not without its challenges. It requires organizational changes and a mindset shift as well as deep technical knowledge to automate the entire process. Depending on your stack you might be using various technologies like Docker, Ansible, Terraform and many others that require a large initial investment to get going.
Infrastructure cost is a potential issue as well since your team is either required to host their own CI server (or fleet) or use a hosted version that suits your needs. Apart from that, you require at least two identical environments (staging and production) that allow you to test out your code, as well as the entire process without disrupting production.
- Commit early. Commit often.
As we've mentioned quite a few times already, this is a fundamental principle to be able to implement CI/CD in your organization. We cannot overstate this.
- Make your pipelines fast.
Making your pipeline fast is a very important requirement for the team to be productive and to enable fast turn around. If a team has to wait an hour long for the pipeline to finish just to be able to deploy a one line change they will get frustrated very quickly.
- Write an extensive test suite (unit and integration tests).
Apart from organizational changes, this is one of the hardest parts to get right. To be successful with CI/CD your team needs to develop a culture of writing tests for each code change they integrate into the master branch. This includes writing unit, integration, regression and smoke tests (to name a few). Without this, your team cannot have the confidence that the changes being deployed are correct and CI/CD will cause more trouble than it's worth.
- Always run smoke tests after a deploy.
We've mentioned smoke tests in the bullet above, but we feel they deserve a special note still. It's very useful to be able to verify that the deployment that went through successfully is, in fact, functioning as expected and has not broken any common user flows.
- Provide an easy way to rollback.
Last but not least, we feel the most important part of a successful CI/CD pipeline is an easy, “one button”, way to rollback your changes in case something goes wrong. Usually, this entails having idempotent deploys where doing a rollback just means re-deploying a previous release.
In the age of distributed systems and cloud computing, as well as ever-increasing complexity, CI/CD can provide your team, and your entire organization, the confidence it needs to deliver software to your customers reliably.
We showcased some key benefits that CI/CD brings as well as some of the best practices to implement it successfully.
If you would like to share your experience with CI/CD, ask a question, mention something that we have not covered, or just say thanks, feel free to comment down below.