TMCnet Feature
August 09, 2022

Kubernetes Services: All You Need To Know

When creating and running a Kubernetes environment, users have to create a series of pods to run particular functions in their platform. For example, one pod could be assigned to image processing, while another focuses on collecting web services. These pods are interchangeable and are often destroyed and created over and over again, with this being an attempt to obtain a desired cluster state.

In order to more effectively manage pods, users will turn to creating Kubernetes services, which are a way of collecting a group of pods into one single location. Users are then able to give this service a name and ClusterIP, both of which can be used to find all the pods within the service.

A Kubernetes service is frequently confused with a Kubernetes deployment, which is where users launch a pod at the same time as their containerized application. Kubernetes deployments ensure that there are always enough replica pods running within a cluster to make it run as efficiently as possible.

A Kubernetes service, on the other hand, is made for managing these pods. Instead of having several disjointed pods that have to work together to enable access, this system ensures that developers have a singular interface that they will then use to access all the services that those pods provide.

What Components Make Up a Kubernetes Service?

As stated, a Kubernetes service acts as a way of connecting many pods into one singular service, with this users then have a much easier time when trying to discover individual pods. Services provide a quick connection between different pods and their services, helping developers to navigate through their own environment.

When creating a Kubernetes service, you’ll have to create the following attributes:

  • A locator - This locator is often in the form of a label selector. This will locate the pods that are going to be placed within the service by the developer.
  • ClusterIP - The IP address and the assigned port number, both of which help with identifying the service and which pods are within.
  • Port Definitions - Ports expose the specific Kubernetes service that has been created, helping to find the specific port within the cluster itself. This also helps pods communicate with the service through the selected port.

These three components are the baseline minimum that every user must employ in order to create a Kubernetes service. Additionally, some developers will also use mapping of any ports that they include within the service, providing each one with a targetPort.

One final note is that developers can create services without pod selectors if they’d like. Instead of selecting individual ports, they could use a service to connect to another service, giving it a different name within their cluster.

What Are The Different Kubernetes Services?

Within the Kubernetes environment, there are four main services that are typically used. Each of these has a different purpose, and will be the preferred method of collecting pods for distinct conditions.

Let’s quickly move through each one of these service types:

  • NodePort - A Kubernetes NodePort service is done through exposing the service through a static port within each node’s IP. Typically, within every open cluster, there are a range of NodePorts. Whenever you use this form of service, you’re able to access the service from outside the cluster by executing <NodeIP.:<NodePort>.
  • ExternalName - With ExternalName, you can access the service through the predefined ExternalName. This is where you can map a specific name to the service and then return the CNAME record value.
  • LoadBalancer - With LoadBalancer, you’re able to expose the specific service through the load balance on your cloud provider. Often, this is the favored approach if you’re using a cloud provider to run your Kubernetes environment, like Azure. Kubernetes automatically creates the load balancer for your cloud provider, with developers only needing to tinker with the firewall rules.
  • ClusterIP - By far the most common method of exposing a service, this is only accessible from the cluster itself. With this, you’re able to type in the IP address internal to the cluster to make use of this service. If you’re running a common environment without much further configuration, this is most likely how you’ll be managing and exposing your Kubernetes service.

Typically, you’ll always be using ClusterIP or NodePort, depending on where you’re accessing your Kubernetes service from. Alternatively, if you’re using a third-party hosting environment like AWS, then LoadBalancer will be your go-to choice.

How Do You Discover a Kubernetes Service Within Your Environment?

There are currently only two different methods that you can use to discover a service within a Kubernetes cluster. The first of these, DNS, is much more common than the second, and will be the main method that you fall back upon.

The two options for discovering a Kubernetes service are:

  • DNS - Whenever you enable DNS inside your Kubernetes environment, it will automatically be added to all of your clusters in Kubernetes, unless you invoke additional configurations. Once this is one, your servers will look out for API requests, with each of these then creating a DNS record. From these records, you’ll easily be able to locate your services.
  • Environment-Based Variable - When a pod is running within a node that’s stationed on an active service, then Kubernetes automatically gives it an environment variable. By then searching for the required variables, you’ll be able to spot any pods within a service, helping you locate the service itself.

A small note is that the second of these only works if your service was created before you created the pods within that service. As this is slightly atypical, the first option is almost always used.

Wrap Up

Kubernetes services are useful tools that help organize your Kubernetes environment while also providing a great deal of functionality. As this tool has evolved over the years, there are now several possible service types you can deploy, as well as two methods of finding the location of your services.

If you’re looking for a way of organizing pods and ensuring they remain active, then Kubernetes services are a must-use for your environment.

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