What to automate? Which parts of the delivery process are good candidates? Which applications will benefit from automation? At first, those sound like silly questions. Automate all your repetitive processes. If you think that you’ll do the same thing manually more than once, automate it. Why would you waste your creative potential and knowledge by doing things that are much better done by scripts? If we can create robots that assemble cars, we can surely create a Jenkins job that builds software, runs tests, and deploys containers. Car assembly is undoubtedly harder to accomplish than building software. Yet, an average company does not adhere to that logic. Why is that?
Two main culprits prevent many companies from automating all the repetitive process; silos and legacy code.
Kubernetes HorizontalPodAutoscaler (HPA) and Cluster Autoscaler (CA) provide essential, yet very rudimentary mechanisms to scale our Pods and clusters. While they do scaling decently well, they do not solve our need to be alerted when there’s something wrong, nor do they provide enough information required to find the cause of an issue. We’ll need to expand our setup with additional tools that will allow us to store and query metrics as well as to receive notifications when there is an issue.
If we focus on tools that we can install and manage ourselves, there is very little doubt about what to use. If we look at the list of Cloud Native Computing Foundation (CNCF) projects, only two graduated so far (October 2018). Those are Kubernetes and Prometheus. Given that we are looking for a tool that will allow us to store and query metrics and that Prometheus fulfills that need, the choice is straightforward. That is not to say that there are no other similar tools worth considering. There are, but they are all service based. We might explore them later but, for now, we’re focused on those that we can run inside our cluster. So, we’ll add Prometheus to the mix and try to answer a simple question. What is Prometheus?
Unlike GKE, EKS does not come with Cluster Autoscaler. We’ll have to configure it ourselves. We’ll need to add a few tags to the Autoscaling Group dedicated to worker nodes, to put additional permissions to the Role we’re using, and to install Cluster Autoscaler.
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-5 application 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
Kubernetes is probably the biggest project we know. It is vast, and yet many think that after a few weeks or months of reading and practice they know all there is to know about it. It’s much bigger than that, and it is growing faster than most of us can follow. How far did you get in Kubernetes adoption?
From my experience, there are four main phases in Kubernetes adoption.
In the first phase, we create a cluster and learn intricacies of Kube API and different types of resources (e.g., Pods, Ingress, Deployments, StatefulSets, and so on). Once we are comfortable with the way Kubernetes works, we start deploying and managing our applications. By the end of this phase, we can shout “look at me, I have things running in my production Kubernetes cluster, and nothing blew up!” I explained most of this phase in The DevOps 2.3 Toolkit: Kubernetes.
Let’s paint a high-level picture of the continuous delivery pipeline. To be more precise, we’ll draw a diagram instead of painting anything. But, before we dive into a continuous delivery diagram, we’ll refresh our memory with the one we used before for describing continuous deployment.
The continuous deployment pipeline contains all the steps from pushing a commit to deploying and testing a release in production.
Continuous delivery removes one of the stages from the continuous deployment pipeline. We do NOT want to deploy a new release automatically. Instead, we want humans to decide whether a release should be upgraded in production. If it should, we need to decide when will that happen. Those (human) decisions are, in our case, happening as Git operations. We’ll comment on them soon. For now, the important note is that the deploy stage is now removed from pipelines residing in application repositories.
The difference between continuous integration, delivery, and deployment is not in processes, but in the level of confidence we have in them.
The continuous deployment process is relatively easy to explain, even though implementation might get tricky. We’ll split our requirements into two groups. We’ll start with a discussion about the overall goals that should be applied to the whole process. To be more precise, we’ll talk about what I consider non-negotiable requirements.