The load balancer in Kubernetes

To work as efficiently as possible with Kubernetes, the workload must be distributed in a manageable way between different pods. This is where the load balancer takes center stage.

What is a load balancer in Kubernetes?

A load balancer is used to distribute the load to be handled by servers or virtual machines to improve overall performance Usually, a load balancer is placed in front of servers to prevent overloading of individual servers. However, we must distinguish between two types of load balancers in Kubernetes:

  • Internal Kubernetes load balancers
  • External Kubernetes load balancers

Internal Kubernetes load balancers

Although the internal Kubernetes load balancers are briefly presented, the article will focus on the external ones. Compared to classic load balancers, an internal load balancer takes a different approach and ensures that only applications running in the same virtual network as your Kubernetes cluster can access it.

External Kubernetes load balancers

External load balancers assign a Kubernetes cluster service node its IP address or DNS name so that it can receive external HTTP requests. This load balancer is a special type of Kubernetes software development service and routes external traffic to individual pods in your cluster. In this way, the best distribution of incoming requests is ensured.

There are several algorithms for configuring load balancers in Kubernetes. The choice depends entirely on how you want to use it. 

What is the Kubernetes load balancer for?

A Kubernetes load balancer defines a service that runs on the cluster, accessed over the public Internet. For a better understanding, you have to take a look at the Kubernetes architecture. A cluster contains multiple nodes, which in turn is made up of multiple pods. Each of these pods is assigned an internal IP that is inaccessible from outside the cluster. This also makes sense, since pods are created and deleted automatically, with IPs reassigned.

A Kubernetes service is often required for software running on pods to be used with a fixed address. In addition to the load balancer, there are other services that are suitable for various application scenarios. But all custom software development services have in common that they attach several pods into a logical unit and describe how to access them:

The Kubernetes load balancer serves to optimally distribute external traffic to the pods of your Kubernetes cluster. Therefore, it can be used in numerous situations, for almost any purpose. The fact that Kubernetes load balancers can direct traffic to each of the pods ensures that the cluster has high availability. If a pod stops working or has errors, the load balancer distributes the tasks among the other pods.

With load balancers, scalability is also improved. If incoming traffic is determined to require less or more resources than are currently available, Kubernetes can respond by automatically creating or deleting pods.

We explain how to create a load balancer for Kubernetes

To create a Kubernetes load balancer, you need your cluster to run in a cloud or an environment that supports setting up external load balancers.

When creating a Kubernetes load balancer with IONOS, the cluster node receives a static IP that allows the service to be addressed from outside the cluster. 

The configuration of a Kubernetes load balancer could, for example, look like this: The service groups pods with the web app selector. Incoming traffic that has used port 8080 along with the load balancer IP is distributed to the individual pods.

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