Proper CI/CD pipelines have become an absolute necessity in a world where application complexity increases continuously. They allow organizations to meet the demand for faster development. These CI/CD pipelines further allow for managing complex deployment requirements to cater to a global audience.
There is no one-size-fits-all approach to creating CI/CD pipelines. Thus, they need to be created depending on the individual requirements. However, there can be some common design considerations when utilizing a widely adapted tool or platform in your applications. In this article, we will look at some of these considerations when creating CI/CD pipelines for Kubernetes.
Understand the Application and Cluster Architecture
The application and the cluster architecture are the first things to consider when dealing with Kubernetes-based development. Creating a CI/CD Kubernetes pipeline boils down to the application and cluster architecture, regardless of the implementation. Different architectures like microservices vs. single container-based applications will have vastly different development and deployment requirements. Thus, understanding the architecture will enable users to properly plan out the necessary stages of their pipelines. It also helps them provision multiple pipelines for separate applications if required, leading to distributed architectures.
Then comes the cluster architecture, which is primarily focused on continuous deployment. The Kubernetes cluster configuration, number of nodes, networking model, and external resources dictate where and how an application can be deployed. Besides, users need to understand the cluster architecture of each individual cluster to carry out deployments in multi-cluster environments. For example, an event-driven application will be well suited for a serverless implementation like Knative. In such cases, the cluster and CI/CD must be tailored to match these serverless workloads rather than traditional containerized deployments.
How to Manage Infrastructure through CI/CD?
Managing the underlying infrastructure and configurations is essential for the longevity of an application. The Kubernetes cluster itself will need configuration changes. Users are responsible for cluster configurations, even when using a managed service that eliminates infrastructure management. Over time, there will be different configuration requirements, from creating K8s ingress points to setting taints and tolerations on nodes to control which Pods get scheduled on them.
Next comes the actual infrastructure. Most modern applications rely on infrastructure resources outside the Kubernetes cluster for different functions, such as firewalls, storage, and security. Each new deployment may require modifications to both configurations and infrastructure, which can be tracked manually. However, it will undoubtedly lead to bottlenecks as deployments get delayed until these modifications are completed.
The solution to these issues is to implement practices like GitOps and Infrastructure as Code. Then codify both Kubernetes configurations and infrastructure changes and manage them through CI/CD as an integrated part of the development process. While this solution will lead to more complex CI/CD pipelines, it will be invaluable for managing infrastructure at scale in the long term.
Selecting the Proper Tools for Kubernetes CI/CD
There are numerous tools and platforms to create CI/CD pipelines. These tools range from popular standalone tools like Jenkins to integrated tools provided by repository services like GitLab CI and GitHub actions. They can be configured to facilitate a Kubernetes-based CI/CD pipeline. However, these tools may lack the features available in dedicated CI/CD tools aimed at Kubernetes environments.
Tools like FluxCD, JenkinsX, and ArgoCD are designed from scratch to facilitate CI/CD for Kubernetes environments. They provide trailer-made features for K8s. Having said that, users should not limit themselves to K8s-based tools. Instead, they can use a combination of different tools to power their pipelines. For example, they can use Jenkins as the continuous integration tool while using ArgoCD for continuous deployments. While this combination will undoubtedly increase the design complexity of the CI/CD pipeline, it will offer the best balance between flexibility and features.
Implementing a Rollback Strategy
Containers provide one of the simplest ways to roll back in case of an issue, allowing users to spin up a new container from an older image quickly. However, it may not be that simple in a production environment, especially when there are changes to cluster configurations or infrastructure. The reason is that you will also have to roll back those changes to previous versions.
Using a deployment strategy like the blue-green deployment allows users to easily point to a working deployment until the issue is fixed. Yet, they will need to adopt a different rollback process for other types of deployment strategies. Implementing GitOps practices with K8s-specific CD tools provides the ideal solution to this issue. It allows users to integrate the application, configurations, and infrastructure changes into a single pipeline in a version-controlled manner and roll back to a previous configuration state from the pipeline itself. Therefore, users need to facilitate rollbacks through CI/CD pipelines themselves when possible.
Conclusion
Kubernetes brings some additional considerations when designing CI/CD pipelines compared to traditional development. By considering the above points, users can create CI/CD pipelines that are tailored for the Kubernetes-based application delivery process.
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