Configuring ingress cluster traffic using an ingress Controller - Configuring ingress cluster traffic | Networking

Using ingress Controllers and routes
Prerequisites
Creating a project and service
Exposing the service by creating a route
Configuring ingress Controller sharding by using route labels
Configuring ingress Controller sharding by using namespace labels
Additional resources

OpenShift Container Platform provides methods for communicating from outside the cluster with services running in the cluster. This method uses an ingress Controller.

Using ingress Controllers and routes

The ingress Operator manages ingress Controllers and wildcard DNS.

Using an ingress Controller is the most common way to allow external access to an OpenShift Container Platform cluster.

An ingress Controller is configured to accept external requests and proxy them based on the configured routes. This is limited to HTTP, HTTPS using SNI, and TLS using SNI, which is sufficient for web applications and services that work over TLS with SNI.

Work with your administrator to configure an ingress Controller to accept external requests and proxy them based on the configured routes.

The administrator can create a wildcard DNS entry and then set up an ingress Controller. Then, you can work with the edge ingress Controller without having to contact the administrators.

By default, every ingress controller in the cluster can admit any route created in any project in the cluster.

The ingress Controller:

Has two replicas by default, which means it should be running on two worker nodes.
Can be scaled up to have more replicas on more nodes.

The procedures in this section require prerequisites performed by the cluster administrator.

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 username
```
Have an OpenShift Container Platform 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

Create a new project for your service by running the oc new-project command:
```
$ oc new-project myproject
```

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

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

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:

Run the oc expose service command to expose the route:

$ oc expose service nodejs-ex

Example output

route.route.openshift.io/nodejs-ex exposed

To verify that the service is exposed, you can use a tool, such as cURL, to make sure the service is accessible from outside the cluster.
1. Use the oc get route command to find the route’s host name:
  $ oc get route
  Example output
  NAME HOST/PORT PATH SERVICES PORT TERMINATION WILDCARD nodejs-ex nodejs-ex-myproject.example.com nodejs-ex 8080-tcp None
2. Use cURL to check that the host responds to a GET request:
  $ curl --head nodejs-ex-myproject.example.com
  Example output
  HTTP/1.1 200 OK ...

Configuring ingress Controller sharding by using route labels

ingress Controller sharding by using route labels means that the ingress Controller serves any route in any namespace that is selected by the route selector.

ingress Controller sharding is useful when balancing incoming traffic load among a set of ingress Controllers and when isolating traffic to a specific ingress Controller. For example, company A goes to one ingress Controller and company B to another.

Procedure

Edit the router-internal.yaml file:

# cat router-internal.yaml
apiVersion: v1
items:
- apiVersion: operator.openshift.io/v1
  kind: ingressController
  metadata:
    name: sharded
    namespace: openshift-ingress-operator
  spec:
    domain: <apps-sharded.basedomain.example.net>
    nodePlacement:
      nodeSelector:
        matchLabels:
          node-role.kubernetes.io/worker: ""
    routeSelector:
      matchLabels:
        type: sharded
  status: {}
kind: List
metadata:
  resourceVersion: ""
  selfLink: ""

Apply the ingress Controller router-internal.yaml file:
```
# oc apply -f router-internal.yaml
```
The ingress Controller selects routes in any namespace that have the label type: sharded.

Configuring ingress Controller sharding by using namespace labels

ingress Controller sharding by using namespace labels means that the ingress Controller serves any route in any namespace that is selected by the namespace selector.

If you deploy the Keepalived ingress VIP, do not deploy a non-default ingress Controller with value HostNetwork for the endpointPublishingStrategy parameter. Doing so might cause issues. Use value NodePort instead of HostNetwork for endpointPublishingStrategy.

Procedure

Edit the router-internal.yaml file:

# cat router-internal.yaml

Example output

apiVersion: v1
items:
- apiVersion: operator.openshift.io/v1
  kind: ingressController
  metadata:
    name: sharded
    namespace: openshift-ingress-operator
  spec:
    domain: <apps-sharded.basedomain.example.net>
    nodePlacement:
      nodeSelector:
        matchLabels:
          node-role.kubernetes.io/worker: ""
    namespaceSelector:
      matchLabels:
        type: sharded
  status: {}
kind: List
metadata:
  resourceVersion: ""
  selfLink: ""

Apply the ingress Controller router-internal.yaml file:
```
# oc apply -f router-internal.yaml
```
The ingress Controller selects routes in any namespace that is selected by the namespace selector that have the label type: sharded.

Additional resources

The ingress Operator manages wildcard DNS. For more information, see ingress Operator in OpenShift Container Platform, Installing a cluster on bare metal, and Installing a cluster on vSphere.