A service is an stable/ consistent endpoint that can be used by other pods/services inside or outside the cluster to access a Pod
Service has two Functions : Permanent IP Address & Load Balancer
Service spans across the entire cluster (As Pods can be on different Nodes)
CoreDNS allows to resolve services using their names
We can access the service using there hostname (Default namespace)
FQDN available for all services : <hostname>.<namespace>.svc.cluster.local
# View all services
kubectl get service
# View service related metadata
kubectl describe serviceService Endpoint
When a Service is created K8s will also create a Service Endpoint
It has the same name as the Service
It is used to keep track of the Pods that are members/endpoints of the Service
# View Endpoints
kubectl get endpointsCluster IP
Default service type (Also called as Internal Service)
Single, internal virtual IP
Only reachable from inside the cluster (Nodes and Pods)
Allows Pods on the cluster to access the service using the Port Number
Multiple ports can also be opened on the service
# Create a ClusterIP Service
kubectl expose deployment httpenv --port 8888
kubectl expose deployment/httpenv --port 8888Headless Service
An Cluster IP Service where .spec.clusterIP is set to None
When Load Balancing and Single Service IP is not required Headless Service can be used
Useful for direct communication between Pods (Sync data between Pods in StatefulSet)
Node Port
Exposes a fixed high port on the Node. Port is open on every Node’s IP
Allows connection to Pods from outside the cluster
Not secure as a port on the Node is directly exposed
Allowed High Port Range : 30,000 - 32,767
Creating a NodePort will automatically create a ClusterIP
kubectl expose deployment httpenv --port 8888 --name httpenv-np --type NodePortLoad Balancer
Also called as External Service (Pod accessible using ipaddress:port)
Control an Load Balancer endpoint outside the Kubernetes Cluster
Only available when infrastructure provider gives an Load Balancer
Creating a LoadBalancer will automatically create NodePort and a ClusterIP
Docker Desktop Kubernetes allows us to use this service
For each app a new service will have to be created (which creates a Load Balancer) due to which this approach can get costly very quickly
kubectl expose deployment httpenv --port 8888 --name httpenv-lb --type LoadBalancerExternal Name
Adds CNAME DNS record to CoreDNS only
Used to give an DNS name to external service outside of the cluster that needs to be accessed by the Pods
Kubernetes NodePort vs LoadBalancer vs Ingress? When should I use what? | Medium