Skip to content

Lab 4 - Multi-Container Pods

30 min Intermediate

Problem

The millennium-falcon service has already been packaged into a container image, but it comes with a special requirement:

  • The legacy app is hard-coded to serve only on port 8989, but the team wants to reach it on the standard web port 8080.

Your task is to build a Pod that runs the legacy container and uses the ambassador pattern to expose it on port 8080. The ambassador is a second container in the same Pod that proxies traffic to the legacy app. Containers in a Pod share a network namespace, so the ambassador can reach the app on 127.0.0.1.

The Pod must meet these requirements:

  • The Pod is named vader-service.
  • It has a container named millennium-falcon that runs the legacy image registry.k8s.io/e2e-test-images/agnhost:2.56 with the arguments netexec and --http-port=8989.
  • It has an ambassador container named nginx-ambassador that runs the quay.io/nginx/nginx-unprivileged:1.29 image and proxies incoming traffic on port 8080 to the legacy service on port 8989.
  • Port 8080 is exposed as a containerPort on the ambassador. You don't need to expose port 8989.

  • The nginx configuration is stored in a ConfigMap named vader-service-ambassador-config, under the key default.conf, with this content:

    server {
    listen 8080;
    location / {
        proxy_pass http://127.0.0.1:8989;
    }
}

  • The ConfigMap is mounted into the ambassador container as a volume at /etc/nginx/conf.d, so the file ends up at /etc/nginx/conf.d/default.conf.

Setup

oc new-project lab4

Verification

Test the service from inside the cluster through port 8080. Create a client Pod to send requests from:

client.yaml
apiVersion: v1
kind: Pod
metadata:
  name: client
spec:
  containers:
    - name: client
      image: registry.access.redhat.com/ubi9/ubi-minimal
      command: ["sleep", "infinity"]

oc apply -f client.yaml
oc wait --for=condition=Ready pod/client pod/vader-service

Call vader-service on port 8080 from the client Pod:

oc exec client -- curl -s "$(oc get pod vader-service -o jsonpath='{.status.podIP}'):8080/echo?msg=The+hyperdrive+needs+repair"

If the ambassador is working, the legacy app echoes back The hyperdrive needs repair.

Cleanup

oc delete project lab4

Relevant documentation: