Updated April 12, 2023
Introduction to Kubernetes Service
In Kubernetes, services are generally a group of pods on the cluster, it is a logical, abstract layer, and here all of the pods perform the same function. This Kubernetes service helps us to enable pods that provide a specific set of functions such as image processing, web service, and many more; this function is assigned a unique IP name and address. So that means if the service is running, that means the IP address will not change till then; also, in order to access the service, we have to follow its policies. In the coming section of the tutorial, we will discuss more about the internal working their implementation in detail for better understanding and clarity for the beginners.
What is Kubernetes service?
As we have already seen about the service, it is a logical, abstract layer, which helps us to connect the sets of pods to the specified abstract service name and the IP address; let take a few points to understand the service in detail;
1) Kubernetes service provides us with the route between the pods and also the discovery.
2) Helps us to connect a set of pods.
3) Kubernetes service helps us to connect our application frontend to its backend.
4) Services use selectors and labels, which helps us match the pods with the other application.
5) It consists of various types of an attribute; some of them are mentioned below;
a) Port definition
b) Label which helps us to connect to the pods
c) Port number and assigned cluster IP address.
d) Mapping of incoming ports to the out coming ports.
Also, in Kubernetes, we have different types of service, which can be discussed in detail in the coming section of the tutorial for better clarity for beginners to understand and implement it in a better way.
How do Kubernetes Services work?
In this section, we will see about the internal working on the Kubernetes service step by step so let’s get started,
1) First, it starts pointing to pods with the help of labels.
2) Also, the Kubernetes service is node-specific; it can still point to the pods, irrespective of where it is currently running in the cluster.
3) We can reach to the application with the help of the Services IP address or the DNS name if the service existed.
This will be clearer once we see the definition and creation of service in the next section of the tutorial.
Kubernetes Service Types
In this section, we will discuss about the different types of service we have in Kubernetes; first, let’s have an overview about each of them; later, we will discuss each of them in detail for better understanding in detailed explanation about each of them, so let’s get started to see below;
1) ExternalName: This service type helps us map the service to a predefined externalName filed.
2) ClusterIp: This type of service helps us to expose a service that can only be accessible with in the cluster.
3) LoadBalacer: this type of service helps us to expose the service with the help of a cloud provider.
4) NodePort: This type of service helps us to expose the service with the help of a static port present on each node IP.
1) Kubernetes ClusterIP service: This is the default service provided by Kubernetes; it mainly uses the IP address to expose the service. But it has one restriction here: it helps us expose the service with the help of an IP address, but it will be internal to the cluster. That means we can access the exposed service within the same cluster itself, not from outside that cluster. This can be sued when we do not want other external services to use our expose service, hence increasing the accessibility part here. In sort, we can say that it helps to expose the service on internal cluster IP if we choose this service, then we will only access the service with the cluster.
2) Kubernetes NodePort service: As this name suggests, this service type helps expose the service on every node port. That means it allows us to open ports on every cluster node. So it will navigate the traffic to every node of the service, even if the service is not running on running on that particular node, thus helping us to handle the traffic as well by navigating it to a different node. It is one of the high-level methods which can be used in development. If we want to connect to the NodePort from outside of any cluster, then we can use this format to connect to them;
3) Kubernetes ExternalName service: As the name suggests here, this type of service can be accessed by the external name assigned to them. Rather than access them via cluster IP etc. In short, if we want to access this service, then we have to use the externalName field, which we define when creating the service. It returns a CNAME record that contains the value of the externalName parameter. In this type of service, no proxy is set up.
4) Kubernetes Load Balancer service: This type of service helps us to expose the service to the cloud provider. Suppose we have a cluster that is running on any of the public clouds, for example, AZURE, AWS, so by creating a load balancer service, it will help us equivalent access like a cluster IP, by expanding this to an external load balancer that will turn specifically to the cloud provider. So Kubernetes will automatically create the environment with all required things like firewall; it will also help us populate the service with an external IP address provided by the cloud provider, create the load balancer, etc.
Create a new instance Kubernetes service
As we already discussed, it is an abstraction layer that is used to define the set of pods; in this section, we will see how to create the Kubernetes service within a reference file; we can define service as a simple REST object, we can create all them, and POST a service definition to the server in order to create the new instance from it. Below is the definition by which we can define a service in the Kubernetes see below;
apiVersion: v1 kind: Service metadata: name: your_name spec: selector: app: name ports: - protocol: TCP port: 80 targetPort: 9376
As you can see, we are trying to define a service here, where we are defining name, version, posts, etc., defining it. Also, we need to mention what kind of REST object it is of use ‘kind’ keyword to define it line above syntax.
1) First, it assigns them in Service IP; the service proxy further uses this IP.
2) We also have a controller for service responsible for scanning the Pods that match the selector of the service. After matching, it sends any updates to that endpoint.
3) Default protocol used by the service is TCP.
4) With the help of service, we can expose as many ports on the service object it is supported by Kubernetes.
In this tutorial, we have seen all the steps needed to take regards to service in Kubernetes, with a detailed explanation about the attribute, components, and different types of service in Kubernetes; go through the whole tutorial it will give you detailed knowledge about the Kubernetes service which will be helpful.
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