Configuring ingress cluster traffic using a load balancer

Configuring ingress cluster traffic using a load balancer

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

Using a load balancer to get traffic into the cluster

If you do not need a specific external IP address, you can configure a load balancer service to allow external access to an OKD cluster.

A load balancer service allocates a unique IP. The load balancer has a single edge router IP, which can be a virtual IP (VIP), but is still a single machine for initial load balancing.

If a pool is configured, it is done at the infrastructure level, not by a cluster administrator.

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 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

Create a new project for your service:

$ oc new-project <project_name>

For example:

$ oc new-project myproject

Use the oc new-app command to create a service. For example:

$ oc new-app \
    -e MYSQL_USER=admin \
    -e MYSQL_PASSWORD=redhat \
    -e MYSQL_DATABASE=mysqldb \
    registry.redhat.io/rhscl/mysql-80-rhel7

Run the following command to see that the new service is created:

$ oc get svc -n myproject

Example output

NAME             TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
mysql-80-rhel7   ClusterIP   172.30.63.31   <none>        3306/TCP   4m55s

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 following command to expose the route:

$ oc expose service <service_name>

For example:

$ oc expose service mysql-80-rhel7

Example output

route "mysql-80-rhel7" exposed

Use a tool, such as cURL, to make sure you can reach the service using the cluster IP address for the service:
```
$ curl <pod_ip>:<port>
```
For example:
```
$ curl 172.30.131.89:3306
```
The examples in this section uses a MySQL service, which requires a client application. If you get a string of characters with the Got packets out of order message, you are connected to the service.

If you have a MySQL client, log in with the standard CLI command:
```
$ mysql -h 172.30.131.89 -u admin -p
```
Example output
```
Enter password:
Welcome to the MariaDB monitor.  Commands end with ; or \g.
MySQL [(none)]>
```

Creating a load balancer service

Use the following procedure to create a load balancer service.

Prerequisites

Make sure that the project and service you want to expose exist.

Procedure

To create a load balancer service:

Log in to OKD.
Load the project where the service you want to expose is located.
```
$ oc project project1
```

Open a text file on the control plane node (also known as the master node) and paste the following text, editing the file as needed:

Sample load balancer configuration file

apiVersion: v1
kind: Service
metadata:
  name: egress-2 (1)
spec:
  ports:
  - name: db
    port: 3306 (2)
  loadBalancerIP:
  loadBalancerSourceRanges: (3)
  - 10.0.0.0/8
  - 192.168.0.0/16
  type: LoadBalancer (4)
  selector:
    name: mysql (5)

1	Enter a descriptive name for the load balancer service.
2	Enter the same port that the service you want to expose is listening on.
3	Enter a list of specific IP addresses to restrict traffic through the load balancer. This field is ignored if the cloud-provider does not support the feature.
4	Enter `Loadbalancer` as the type.
5	Enter the name of the service.

To restrict traffic through the load balancer to specific IP addresses, it is recommended to use the service.beta.kubernetes.io/load-balancer-source-ranges annotation rather than setting the loadBalancerSourceRanges field. With the annotation, you can more easily migrate to the OpenShift API, which will be implemented in a future release.

Save and exit the file.
Run the following command to create the service:
```
$ oc create -f <file-name>
```
For example:
```
$ oc create -f mysql-lb.yaml
```

Execute the following command to view the new service:

$ oc get svc

Example output

NAME       TYPE           CLUSTER-IP      EXTERNAL-IP                             PORT(S)          AGE
egress-2   LoadBalancer   172.30.22.226   ad42f5d8b303045-487804948.example.com   3306:30357/TCP   15m

The service has an external IP address automatically assigned if there is a cloud provider enabled.

On the master, use a tool, such as cURL, to make sure you can reach the service using the public IP address:
```
$ curl <public-ip>:<port>
```
For example:
```
$ curl 172.29.121.74:3306
```
The examples in this section use a MySQL service, which requires a client application. If you get a string of characters with the Got packets out of order message, you are connecting with the service:

If you have a MySQL client, log in with the standard CLI command:
```
$ mysql -h 172.30.131.89 -u admin -p
```
Example output
```
Enter password:
Welcome to the MariaDB monitor.  Commands end with ; or \g.
MySQL [(none)]>
```