Red Hat OpenShift Development I: Introduction to Containers with Podman

Instructions

1. Log in to the cluster as the developer user, and ensure that you use the ocp-applications project.

   1. Log in to the cluster as the developer user.

      [student@workstation ~]$ oc login -u developer -p developer \
      https://api.ocp4.example.com:6443
      Login successful.
      
      ...output omitted...

   2. Ensure that you use the ocp-applications project.

      [student@workstation ~]$ oc project ocp-applications
      Already on project "ocp-applications" on server "https://api.ocp4.example.com:6443".

2. Explore the podman-hello-client application.

   1. Open the ~/DO188/labs/openshift-applications/podman-hello-client/Containerfile file in a text editor, such as gedit.

      Note the default environment variable values and the CMD instruction:

      FROM registry.access.redhat.com/ubi8/ubi-minimal:8.6
      
      ARG PROTO="http" \
          URL="hello-server-svc" \
          PORT="3000" \
          ENDPOINT="greet"
      
      ENV PROTO=${PROTO} \
          URL=${URL} \
          PORT=${PORT} \
          ENDPOINT=${ENDPOINT}
      
      ...Containerfile omitted...
      
      CMD ["./client.sh"]

   2. Open the ~/DO188/labs/openshift-applications/podman-hello-client/client.sh file in a text editor, such as gedit.

      Note that the client uses the environment variables in the following format:

      ...script omitted...
      curl ${OPTS} "${PROTO}://${URL}:${PORT}/${ENDPOINT}"
      ...script omitted...

      This means that the client sends requests to the http://hello-server-svc:3000/greet URL by default.

3. Explore the deployed application in the ocp-applications project by using the RHOCP Web Console.

   1. In a web browser, navigate to https://console-openshift-console.apps.ocp4.example.com. Select the htpasswd_provider user provider, and log in with the following credentials:

      • Username: developer

      • Password: developer

      Click Skip tour if prompted.

   2. Click ocp-applications, then click the overflow menu and select Topology. Note the hello-server and hello-client application pods.

   3. Click the hello-server pod. Notice the hello-server-svc service.

      The service serves on port 3000 and routes requests to the port 3000 inside the hello-server pod.

   4. Click the hello-client pod. Then, view the application logs by clicking View logs.

      The hello-client application sends requests to the http://hello-server-svc:3000/greet URL and prints the {"hello": "world"} response to the console.

   5. Return to the Topology view by clicking the Red Hat OpenShift logo.

4. Modify the hello-server-svc service to serve on the 8080 port.

   1. Click the hello-server pod. Then, click the hello-server-svc service.

   2. Click the YAML tab. In the text editor, scroll to the spec.ports object and change the port property to the 8080 value:

      ...YAML omitted...
      spec:
        ports:
          - protocol: TCP
            port: 8080
            targetPort: 3000
      ...YAML omitted...

      Click Save.

   3. Verify the service port mapping.

      Click the Details tab and verify that the Port Mapping section contains the 8080 Port and the 3000 Pod port or name values.

5. Modify the hello-client pod to use the 8080 port.

   1. Return to the terminal window and verify that the oc command is logged in with the RHOCP API.

      [student@workstation ~]$ oc whoami --show-context
      ocp-applications/api-ocp4-example-com:6443/developer

   2. Display the last line of the hello-client pod logs.

      [student@workstation ~]$ oc logs hello-client | tail -n 1
      empty line expected

      In the preceding instruction, the output of the oc logs hello-client command is used as the input for the tail command. The tail -n 1 command displays the last line of the output.

      The result is empty because hello-client cannot reach the hello-server pod on port 3000.

   3. Delete the hello-client pod.

      [student@workstation ~]$ oc delete pod hello-client
      pod "hello-client" deleted

   4. Recreate the hello-client pod. Set the PORT environment variable to the 8080 value and use the registry.ocp4.example.com:8443/redhattraining/podman-hello-client:latest image.

      [student@workstation ~]$ oc run hello-client --env PORT=8080 \
        --image registry.ocp4.example.com:8443/redhattraining/podman-hello-client:latest
      pod "hello-client" created

   5. Verify that the hello-client pod is in the Running status.

      [student@workstation ~]$ oc get pod
      NAME           READY   STATUS    RESTARTS   AGE
      hello-client   1/1     Running   0          32s
      hello-server   1/1     Running   0          83m

   6. Display the last line of the hello-client pod logs.

      [student@workstation ~]$ oc logs hello-client | tail -n 1
      {"hello":"world"}

      This means that the hello-client pod can reach the hello-server pod.