How to call services internally in k8s?

In Kubernetes, a Service is an abstraction used to expose a group of Pods to other services or external networks. Services can be accessed through Cluster IP (internal IP) for intercommunication. Here are some methods to achieve Service intercommunication in Kubernetes.

1. Using the service name: You can achieve mutual calls between services by using the service name in the application of the calling party. Kubernetes will automatically resolve the service name to the service’s cluster IP address.
2. Environment variable: One option is to set the Cluster IP address of the service that needs to be called as an environment variable, and then use this environment variable in the application code of the calling party to make mutual calls.
3. DNS resolution: Kubernetes has a built-in DNS service that allows for DNS resolution using the service’s name. This means that the service’s Cluster IP address can be retrieved by directly using the service’s name for DNS resolution in the calling application.
4. Headless Service is a unique type of service that does not assign a Cluster IP, instead returning a list of IP addresses for all pods directly. It can be used to enable direct communication between pods without passing through the service layer.

It’s important to note that when services call each other, it’s typically done based on the service’s name and Cluster IP address, rather than directly using the Pod’s IP address. This helps to improve portability and maintainability, as Pod IP addresses can change whereas service names and Cluster IP addresses remain stable.