Services

  • K8s service allows you to attach a static Ip address and DNS name for a set of pods

  • Services allows you to persist an address for a pod even if it dies.

  • Pod without service will have dynamic ip

Service types:

  1. ClusterIP: (Randomly forwar traffic to any pod)

  2. Headless: (Traffic to specifi pod eg: database)

  3. NodePort: (Uses worker node ip address)

  4. LoadBalancer: (Balances the traffic)

  5. ExternalName: Service that does not have selectors and uses DNS names instead.

Services traffic policies

Services allows you to set traffic policies to determine how ingress traffic is routed.

Traffic policies:

  • External Traffic policy:

    • Cluster: Route external traffic to all ready endpoints

    • Local: Only route to ready node-local endpoings

  • Internal traffic policy: How traffic from internal sources is routed

If traffic policy is local and there are no node-local endpoints, then kubeproxy does not forward any traffic for the relevant service

ClusterIP:

  • Default service type

  • Used for internal traffic

NodePort:

Nodeport allows you to expose a port for virtual machines running pods that service is managing.

port: 80
targetPort: 8080

Loadbalancer:

  • A loadbalancer service type allows you to use an external load balancer

  • Usually managed by third party

  • It is well suited for production workloads. Generally to use K8s ingress

Headless:

  • It is a service with no ClusterIP address

  • Does not provide load balancing or proxying

ExternalName:

ExternalName services as the same as ClusterIP service with exception instead of returning staticIP it returns a CNAME records

Kubectl expose command:

kubectl expose deployment my-app 
--type=NodePort\
--name=my-svc\
--port=80\
--targetport=8080\ 
--nodeport=3000

Busybox:

  • BusyBox combines tiny versions of many common UNIX utilities into single small executable

  • Can be used to interactively debug services.

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