Flux v2 is a tool for converging the actual state (Kubernetes clusters) into the desired state defined in Git. It is a GitOps-based deployment mechanism often used in continuous delivery (CD) processes.
Argo CD is a declarative GitOps deployment tool for Kubernetes.
It is one of the best, if not the best tool we have today to deploy applications inside Kubernetes clusters. It is based on GitOps principles, and it is a perfect fit to be a part of continuous delivery pipelines. It provides all the building blocks we might need if we would like to adopt GitOps principles for deployments and inject them inside the process of application lifecycle management.
Argo CD is a tool that helps us forget the existence of
helm install, and similar commands. It is a mechanism that allows us to focus on defining the desired state of our environments and pushing definitions to Git. It is up to Argo CD to figure out how to converge our desires into reality.
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.
A while ago, we (Viktor Farcic and Darin Pope) thought it would be a good idea to add an out-of-the-box option to use canary deployments in Jenkins X. We should have finished it by now, and yet we did not even start working on it. Instead of just adding it to Jenkins X, we spent considerable time exploring the subject.
Knowing that HorizontalPodAutoscaler (HPA) manages auto-scaling of our applications, the question might arise regarding
replicas. Should we define them in our Deployments and StatefulSets, or should we rely solely on HPA to manage them? Instead of answering that question directly, we’ll explore different combinations and, based on results, define the strategy.
First, let’s see how many Pods we have in our cluster right now.
You might not be able to use the same commands since they assume that
go-demo-5application is already running, that the cluster has HPA enabled, that you cloned the code, and a few other things. I presented the outputs so that you can follow the logic without running the same commands.
kubectl -n go-demo-5 get pods
The output is as follows.
NAME READY STATUS RESTARTS AGE api-... 1/1 Running 0 27m api-... 1/1 Running 2 31m db-0 2/2 Running 0 20m db-1 2/2 Running 0 20m db-2 2/2 Running 0 21m
We can see that there are two replicas of the
api Deployment, and three replicas of the
This article is part of the series that compares Kubernetes and Docker Swarm features.
- Kubernetes Pods, ReplicaSets, And Services Compared To Docker Swarm Stacks
- Kubernetes Deployments Compared To Docker Swarm Stacks
- Kubernetes Ingress Compared To Docker Swarm Equivalent
- Kubernetes ConfigMaps Compared To Docker Swarm Configs
- Kubernetes Secrets Compared To Docker Swarm Secrets
- Kubernetes Namespaces Compared To Docker Swarm Equivalent (If There Is Any)
- Kubernetes RBAC Compared To Docker Swarm RBAC
- Kubernetes Resource Management Compared To Docker Swarm Equivalent
If you already used Docker Swarm, the logic behind Kubernetes Deployments should be familiar. Both serve the same purpose and can be used to deploy new applications or update those that are already running inside a cluster. In both cases, we can easily deploy new releases without any downtime (when application architecture permits that).
However, unlike the previous comparison between Kubernetes Pods, ReplicaSets, And Services, on the one hand, and Docker Swarm Stacks on the other, Deployments do provide a few potentially important functional differences. But, before we dive into functionals comparison, we’ll take a moment to explore differences in how we define objects.
This article is part of the Continuous Integration, Delivery and Deployment series.
The previous article described several ways to implement Continuous Deployment. Specifically, it described, among other things, how to implement it using Docker to deploy applications as containers and nginx for reverse proxy necessary for successful utilization of blue-green deployment technique. All that was running on top of CoreOS, operating system specifically designed for running Docker containers.
The waterfall model originated in manufacturing and construction where changes are costly and investment in design of the production line is often much less than potential loss if the actual production fails. It is based on idea that planning and design costs are much lower than those used in the actual production.
## Software development life-cycle (SDLC)
The software waterfall model often uses some variation of following phases:
- Requirements specification (Requirements Analysis) resulting in Requirements Document
- Software design resulting in Software Design (SD) document
- Implementation resulting in the actual software
- Testing (or Validation)
- Deployment (or Installation)