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Services & Networking

Services

An abstract way to expose an application running on a set of Pods as a network service.

Kubernetes Pods are mortal. They are born and when they die, they are not resurrected. If you use a Deployment to run your app, it can create and destroy Pods dynamically.

Each Pod gets its own IP address, however in a Deployment, the set of Pods running in one moment in time could be different from the set of Pods running that application a moment later.

In Kubernetes, a Service is an abstraction which defines a logical set of Pods and a policy by which to access them (sometimes this pattern is called a micro-service). The set of Pods targeted by a Service is usually determined by a selector (see below for why you might want a Service without a selector).

If you’re able to use Kubernetes APIs for service discovery in your application, you can query the API server for Endpoints, that get updated whenever the set of Pods in a Service changes.

For non-native applications, Kubernetes offers ways to place a network port or load balancer in between your application and the backend Pods.

Resources

IKS & OpenShift

References

apiVersion: apps/v1
kind: Deployment
metadata:
name: my-deployment
labels:
app: nginx
version: v1
spec:
replicas: 3

Get Service

oc get svc

Get Service Description

oc describe svc my-service

Expose a service

oc expose service <service_name>

Get Route for the Service

oc get route

Routes

(OpenShift Only)

Routes are Openshift objects that expose services for external clients to reach them by name.

Routes can insecured or secured on creation using certificates.

The new route inherits the name from the service unless you specify one using the —name option.

Resources

OpenShift

References

Route Creation

apiVersion: v1
kind: Route
metadata:
name: frontend
spec:
to:
kind: Service
name: frontend

Secured Route Creation

apiVersion: v1
kind: Route
metadata:
name: frontend
spec:
to:
kind: Service
name: frontend
tls:

Commands

Create Route from YAML

oc apply -f route.yaml

Get Route

oc get route

Describe Route

oc get route <route-name>

Get Route YAML

oc get route <route-name> -o yaml

Ingress

An API object that manages external access to the services in a cluster, typically HTTP.

Ingress can provide load balancing, SSL termination and name-based virtual hosting.

Ingress exposes HTTP and HTTPS routes from outside the cluster to services within the cluster. Traffic routing is controlled by rules defined on the Ingress resource.

Resources

OpenShift

IKS

References

apiVersion: networking.k8s.io/v1beta1 # for versions before 1.14 use extensions/v1beta1
kind: Ingress
metadata:
name: example-ingress
spec:
rules:
- host: hello-world.info
http:
paths:

View Ingress Status

oc describe clusteroperators/ingress

Describe default Ingress Controller

oc describe --namespace=openshift-ingress-operator ingresscontroller/default

Activities

TaskDescriptionLink
Try It Yourself
Creating ServicesCreate two services with certain requirements.Setting up Services
IKS Ingress ControllerConfigure Ingress on Free IKS ClusterSetting IKS Ingress