15.4. Configuring ingress cluster traffic using a load balancer


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

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

注意

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

注意

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

15.4.2. 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
    Copy to Clipboard Toggle word wrap
  • 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.

15.4.3. 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:

    $ oc new-project <project_name>
    Copy to Clipboard Toggle word wrap

    For example:

    $ oc new-project myproject
    Copy to Clipboard Toggle word wrap
  2. 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
    Copy to Clipboard Toggle word wrap
  3. Run the following command to see that the new service is created:

    $ oc get svc -n myproject
    Copy to Clipboard Toggle word wrap

    Example output

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

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

15.4.4. 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 OpenShift Container Platform.
  2. Log in to the project where the service you want to expose is located:

    $ oc project myproject
    Copy to Clipboard Toggle word wrap
  3. Run the following command to expose the route:

    $ oc expose service <service_name>
    Copy to Clipboard Toggle word wrap

    For example:

    $ oc expose service mysql-80-rhel7
    Copy to Clipboard Toggle word wrap

    Example output

    route "mysql-80-rhel7" exposed
    Copy to Clipboard Toggle word wrap

  4. 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>
    Copy to Clipboard Toggle word wrap

    For example:

    $ curl 172.30.131.89:3306
    Copy to Clipboard Toggle word wrap

    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
    Copy to Clipboard Toggle word wrap

    Example output

    Enter password:
    Welcome to the MariaDB monitor.  Commands end with ; or \g.
    
    MySQL [(none)]>
    Copy to Clipboard Toggle word wrap

15.4.5. 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:

  1. Log in to OpenShift Container Platform.
  2. Load the project where the service you want to expose is located.

    $ oc project project1
    Copy to Clipboard Toggle word wrap
  3. Open a text file on 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:
      type: LoadBalancer 
    3
    
      selector:
        name: mysql 
    4
    Copy to Clipboard Toggle word wrap

    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 loadbalancer as the type.
    4
    Enter the name of the service.
  4. Save and exit the file.
  5. Run the following command to create the service:

    $ oc create -f <file-name>
    Copy to Clipboard Toggle word wrap

    For example:

    $ oc create -f mysql-lb.yaml
    Copy to Clipboard Toggle word wrap
  6. Execute the following command to view the new service:

    $ oc get svc
    Copy to Clipboard Toggle word wrap

    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
    Copy to Clipboard Toggle word wrap

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

  7. 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>
    Copy to Clipboard Toggle word wrap

    For example:

    $ curl 172.29.121.74:3306
    Copy to Clipboard Toggle word wrap

    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
    Copy to Clipboard Toggle word wrap

    Example output

    Enter password:
    Welcome to the MariaDB monitor.  Commands end with ; or \g.
    
    MySQL [(none)]>
    Copy to Clipboard Toggle word wrap

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