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, 19:14, 14 November 2023
https://kubernetes.io/docs/concepts/services-networking/ gives a deep dive into the various capabilities around exposing services and the networking models in Kubernetes.
Service is a top-level resource in the Kubernetes REST API. You can find more details about the [https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.28/#service-v1-core Service API object]
== Example ==
Service Config to load balance traffic across all Pods with the app=nginx label. Receives on and sends to port 80. Exposes an externally accessible endpoint.
<syntaxhighlight lang="yaml">
kind: Service
apiVersion: v1
metadata:
# Unique key of the Service instance
name: service-example
spec:
ports:
# Accept traffic sent to port 80
- name: http
port: 80
targetPort: 80
selector:
# Loadbalance traffic across Pods matching
# this label selector
app: nginx
# Create an HA proxy in the cloud provider
# with an External IP address - *Only supported
# by some cloud providers*
type: LoadBalancer
</syntaxhighlight>
== Service Type ==
(''quoted from the documentation <ref>https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.28/#service-v1-core</ref>'')
type determines how the Service is exposed. Defaults to '''ClusterIP'''. Valid options are '''ExternalName''', '''ClusterIP''', '''NodePort''', and '''LoadBalancer'''. "ClusterIP" allocates a cluster-internal IP address for load-balancing to endpoints. Endpoints are determined by the selector or if that is not specified, by manual construction of an Endpoints object or EndpointSlice objects. If clusterIP is "None", no virtual IP is allocated and the endpoints are published as a set of endpoints rather than a virtual IP. "NodePort" builds on ClusterIP and allocates a port on every node which routes to the same endpoints as the clusterIP. "LoadBalancer" builds on NodePort and creates an external load-balancer (if supported in the current cloud) which routes to the same endpoints as the clusterIP. "ExternalName" aliases this service to the specified externalName. Several other fields do not apply to ExternalName services. More info: https://kubernetes.io/docs/concepts/services-networking/service/#publishing-services-service-types
There is a good [https://medium.com/@badawekoo/different-ways-to-expose-services-in-kubernetes-70177e63e27b Medium article about the different types of services in Kubernetes], with the official documentation at https://kubernetes.io/docs/concepts/services-networking/service/#publishing-services-service-types
; <tt>type: ClusterIP</tt>
: expose pods only inside your kubernetes cluster. You can make them public using an [https://kubernetes.io/docs/concepts/services-networking/ingress/ Ingress] or a [https://gateway-api.sigs.k8s.io/ Gateway]
; <tt>type: NodePort</tt>
: expose services on a static port
; <tt>type: LoadBalancer</tt>
: something
; <tt>type: ExternalName</tt>
{{References}}
[[Category:Kubernetes]]
