K
Q

kubernetes service - can the same port value (ie 10002) be used on 3 different variable values (port, targetport, nodeport)?

5/10/2019

kubernetes service - can the same port value (ie 10002) be used on 3 different variable values (port, targetport, nodeport)?

ie

spec:
  type: NodePort
  ports:
  - port: 10002
    name: webapi
    targetPort: 10002
    nodePort: 10002
-- tooptoop4
docker
kubernetes
kubernetes-ingress

Similar Questions

Use HTTP traffic for internal communication in WSO2 API Management across all components
Error in Transport for helm install package
How to create PV exclusively for a pod
Share one master node across multiple clusters
Access pod application by pod IP outside Cluster

2 Answers

5/10/2019

service ip and port are virtual. they are not attached to network interface. you can use any port for service port. it need not be same as pods target port.

default nodeport range in kubernetes is 30000-32767. you can also define custom range.

so, it is possible to have same port for pod/server/nodeport, if the port is open for connection

-- P Ekambaram
Source: StackOverflow
5/10/2019

In k8s Service Spec

TargetPort: Pod's port

Port: Service's port

NodePort: Nodepool's port

Thus, port and targetport needs to be same, and value of nodeport comes dynamically. (default: 30000-32767)

You can get detail info with the following command kubectl explain service.spec.ports

FIELDS:
   name <string>
     The name of this port within the service. This must be a DNS_LABEL. All
     ports within a ServiceSpec must have unique names. This maps to the 'Name'
     field in EndpointPort objects. Optional if only one ServicePort is defined
     on this service.

   nodePort     <integer>
     The port on each node on which this service is exposed when type=NodePort
     or LoadBalancer. Usually assigned by the system. If specified, it will be
     allocated to the service if unused or else creation of the service will
     fail. Default is to auto-allocate a port if the ServiceType of this Service
     requires one. More info:
     https://kubernetes.io/docs/concepts/services-networking/service/#type-nodeport

   port <integer> -required-
     The port that will be exposed by this service.

   protocol     <string>
     The IP protocol for this port. Supports "TCP" and "UDP". Default is TCP.

   targetPort   <string>
     Number or name of the port to access on the pods targeted by the service.
     Number must be in the range 1 to 65535. Name must be an IANA_SVC_NAME. If
     this is a string, it will be looked up as a named port in the target Pod's
     container ports. If this is not specified, the value of the 'port' field is
     used (an identity map). This field is ignored for services with
     clusterIP=None, and should be omitted or set equal to the 'port' field.
     More info:
     https://kubernetes.io/docs/concepts/services-networking/service/#defining-a-service

If you want a specific port number, you can specify a value in the nodePort field, and the system will allocate you that port or else the API transaction will fail (i.e. you need to take care about possible port collisions yourself). The value you specify must be in the configured range for node ports. nodeport

-- Suresh Vishnoi
Source: StackOverflow