Configuring ingress cluster traffic using a NodePort

OKD provides methods for communicating from outside the cluster with services running in the cluster. This method uses a NodePort.

Using a NodePort to get traffic into the cluster

Use a NodePort-type Service resource to expose a service on a specific port on all nodes in the cluster. The port is specified in the Service resource’s .spec.ports[*].nodePort field.

A NodePort exposes the service on a static port on the node’s IP address. NodePorts are in the 30000 to 32767 range by default, which means a NodePort is unlikely to match a service’s intended port. For example, port 8080 may be exposed as port 31020 on the node.

The administrator must ensure the external IP addresses are routed to the nodes.

NodePorts and external IPs are independent and both can be used concurrently.

Prerequisites

Before starting the following procedures, the administrator must:

• Set up the external port to the cluster networking environment so that requests can reach the cluster.

• Make sure there is at least one user with cluster admin role. To add this role to a user, run the following command:

  $ oc adm policy add-cluster-role-to-user cluster-admin <user_name>

• Have an OKD cluster with at least one master and at least one node and a system outside the cluster that has network access to the cluster. This procedure assumes that the external system is on the same subnet as the cluster. The additional networking required for external systems on a different subnet is out-of-scope for this topic.

Creating a project and service

If the project and service that you want to expose do not exist, first create the project, then the service.

If the project and service already exist, skip to the procedure on exposing the service to create a route.

Prerequisites

• Install the oc CLI and log in as a cluster administrator.

Procedure

1. Create a new project for your service by running the oc new-project command:

   $ oc new-project myproject

2. Use the oc new-app command to create your service:

   $ oc new-app nodejs:12~https://github.com/sclorg/nodejs-ex.git

3. To verify that the service was created, run the following command:

   $ oc get svc -n myproject

   Example output

   NAME        TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
   nodejs-ex   ClusterIP   172.30.197.157   <none>        8080/TCP   70s

   By default, the new service does not have an external IP address.

Exposing the service by creating a route

You can expose the service as a route by using the oc expose command.

Procedure

To expose the service:

1. Log in to OKD.

2. Log in to the project where the service you want to expose is located:

   $ oc project myproject

3. To expose a node port for the application, modify the custom resource definition (CRD) of a service by entering the following command:

   $ oc edit svc <service_name>

   Example output

   spec:
     ports:
     - name: 8443-tcp
       nodePort: 30327 (1)
       port: 8443
       protocol: TCP
       targetPort: 8443
     sessionAffinity: None
     type: NodePort (2)

   1	Optional: Specify the node port range for the application. By default, OKD selects an available port in the 30000-32767 range.
   2	Define the service type.

4. Optional: To confirm the service is available with a node port exposed, enter the following command:

   $ oc get svc -n myproject

   Example output

   NAME                TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
   nodejs-ex           ClusterIP   172.30.217.127   <none>        3306/TCP         9m44s
   nodejs-ex-ingress   NodePort    172.30.107.72    <none>        3306:31345/TCP   39s

5. Optional: To remove the service created automatically by the oc new-app command, enter the following command:

   $ oc delete svc nodejs-ex

Verification

• To check that the service node port is updated with a port in the 30000-32767 range, enter the following command:

  $ oc get svc

  In the following example output, the updated port is 30327:

  Example output

  NAME    TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
  httpd   NodePort   172.xx.xx.xx    <none>        8443:30327/TCP   109s

Additional resources

• Configuring the node port service range