What are Kubernetes deployments? What's a Kubernetes service? What key differences would a "Kubernetes deployment vs service" analysis reveal?
Aren't they both abstractions in Kubernetes?
If so... what's the difference? What does what?
Let's get you some answers now:
1. But First: What Is Kubernetes Deployment?
A question that must have preceded your:
"What's the difference between deployment and service in Kubernetes?"
Now, here's a concise and accurate definition for you:
Kubernetes deployment is an abstraction describing how your application will be deployed.
It describes your Kubernetes cluster and defines:
- the no. of instances that should be running once your app gets deployed in Kubernetes
- other parameters and settings needed for running your application
2. What Exactly Are Kubernetes Services?
Your "What are Kubernetes deployment?" question must surely have been followed by this one here.
So, let's shed some light on the notion of "Kubernetes as a service", as well:
It's an abstraction that describes your Kubernetes cluster.
Its role is to make your application available to the networks that your cluster's connected to. In short, it exposes it to the outside world...
Now, here's how it works precisely:
Your application service gets a network request. Then, it makes an inventory of all those Pods in your Kubernetes cluster that match the service's selector, picks one and forwards it to the network requesting it.
In a nutshell, a service in Kubernetes is no more than a load balancer in Kubernetes. It will just send traffic to your app in a round-robin way: network requests get spread across the ecosystem of the running pods.
3. Kubernetes Deployment vs Service: How Are They Different?
But first, let's outline that one thing that Kubernetes service and deployment have in common:
They're both Kubernetes abstractions.
But while Kubernetes deployment is "in charge" with keeping the pods running in the cluster, a service is in charge of granting network access to those pods.
For instance, you can use either a service or a deployment on its own:
- if you opt for using a Kubernetes service without a deployment, you'll just need to create your pods one by one. The service will forward network requests to your set of pods based on their labels
- if you opt for using Kubernetes deployment without a service, you can replicate your pods and access them one by one through direct network requests. You get to scale the deployment of your app up and down
4. What Is the Difference Between POD and Deployment in Kubernetes?
But first: "What's a POD?"
It's an abstraction in Kubernetes made of a set of application containers (or just one) and their shared resources (shared storage, information about how each container should be run, networking, etc.).
And here's POD in relation to a Kubernetes deployment:
Once you set up a deployment, it will automatically create pods, incorporating multiple containers. Each pod is connected to the Node. Once that Node fails, your identical PODs will get scheduled on other variable Nodes included in your Kubernetes cluster.
And going back to our Kubernetes deployment vs service analysis, here's another difference for you to consider:
Pods in Kubernetes Services depend on Nodes. Once a node is no longer available, those pods' lifecycle ends, as well. On the other hand, you won't find this type of dependency relation between Pods and nodes in a Kubernetes deployment.
5. In Conclusion...
All Kubernetes deployment vs service analysis will reveal to you 3 key aspects:
- deployments and services in Kubernetes might look similar, judging by their functionality, yet there are obvious differences between them
- the efficiency of each approach depends greatly on the type of Kubernetes project and its level of complexity
- Kubernetes service and deployment can work together in harmony
Is your "service vs deployment in Kubernetes" dilemma any less... "severe" now?
Is it any clearer for you how these 2 abstractions are different? Have you already used any of these approaches?