Deployment strategies affect everyone, no matter whether we are focused only on a single aspect of the application lifecycle or we are in full control. The way we deploy affects the architecture, testing, monitoring, and many other aspects. And not only that, but we can say that architecture, testing, and monitoring affect the way we deploy. All those things are closely related and affect each other.
We'll discuss different deployment strategies and answer a couple of questions. Is your application stateful or stateless? Does its architecture permit scaling? How do you roll back? How do you scale up and down? Do you need your application to run always? Should you use Kubernetes Deployments instead of, let's say, StatefulSets? Answers to those questions will not serve much unless we are familiar with some of the most commonly used deployment strategies. Not only that knowledge will help us choose which one to pick, but they might even influence the architecture of our applications.
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What's wrong with jx create cluster and jx install commands? Why do we need a different way to install, manage, and upgrade Jenkins X? Those are ad-hoc commands that do not follow GitOpts principles. They are not idempotent (you cannot run them multiple times and expect the same result). They are not stored in Git, at least not in a form that the system can interpret and consume in an attempt to converge the desired into the actual state. They are not declarative.
Serverless deployments are gaining traction. Today, we have quite a few choices for converting our applications into serverless inside Kubernetes cluster. One of those, my favorite, is Knative. We'll explore how we can combine it with Jenkins X to create a fully automated continuous deployment pipeline that deploys serverless applications.
Jenkins X itself is serverless. That helps with many things, with better resource utilization and scalability being only a few of the benefits. Can we do something similar with our applications? Can we scale them to zero when no one is using them? Can we scale them up when the number of concurrent requests increases? Can we make our applications serverless?
Hopefully, this is not the first time you created a quick start project, and you are already familiar with the out-of-the-box pipeline our new application inherited from a build pack. Also, I will assume that you do understand that buildPack: go instruction in jenkins-x.yml means that the pipeline inherits all the steps defined in the corresponding build pack.
Our pipeline is currently building a Linux binary of our application before adding it to a container image. But what if we'd like to distribute the application also as executables for different operating systems? We could provide that same binary, but that would work only for Linux users since that is the architecture it is currently built for. We might want to extend the reach to Windows and MacOS users as well, and that would mean that we'd need to build two additional binaries. How could we do that?
Without TLS certificates the applications we install are accessible through a plain HTTP protocol. As I'm sure you're aware, that is not acceptable. All public-facing applications should be available through HTTPS only, and that means that we need TLS certificates. We could generate them ourselves for each of the applications, but that would be too much work. Instead, we'll try to figure out how to create and manage the certificates automatically. Fortunately, Jenkins X already solved that and quite a few other Ingress-related challenges. We just need to learn how to tell jx what exactly we need.
Jenkins X main logic is based on applying GitOps principles. Every change must be recorded in Git, and only Git is allowed to initiate events that result in changes in our clusters. That logic is the cornerstone of Jenkins X, and it served us well so far. However, there are actions we might need to perform that do not result in changes to the source code or configurations. Hence the emergence of ChatOps.
The serverless flavor of Jenkins X or, as some call it, Jenkins X Next Generation, is an attempt to redefine how we do continuous delivery and GitOps inside Kubernetes clusters. It does that by combining quite a few tools into a single easy-to-use bundle. As a result, most people will not have a need to understand intricacies of how the pieces work independently, nor how they are all integrated. Instead, many will merely push a change to Git and let the system do the rest. But, there are always those who would like to know what's happening behind the hood. To satisfy those craving for insight, we'll explore the processes and the components involved in the serverless Jenkins X platform. Understanding the flow of an event initiated by a Git webhook will give us insight into how the solution works and help us later on when we go deeper into each of the new components.