Forwarding Port Traffic with an Ambassador Container

1.5 hours
  • 2 Learning Objectives

About this Hands-on Lab

Multi-container pods provide a variety of ways to enhance containers. When using the ambassador design pattern, a secondary container can intercept and translate network traffic before passing it on to the main container. In this lab, you will have a chance to implement a multi-container pod using the ambassador model. You will use an ambassador container running HAProxy to proxy traffic to a legacy service on a different port. After completing this exercise, you will have a hands-on understanding of how the ambassador model can be implemented.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Create a ConfigMap containing the configuration for the HAProxy ambassador.

Create a YAML definition file called fruit-service-ambassador-config.yml.

apiVersion: v1
kind: ConfigMap
metadata:
  name: fruit-service-ambassador-config
data:
  haproxy.cfg: |-
    global
        daemon
        maxconn 256

    defaults
        mode http
        timeout connect 5000ms
        timeout client 50000ms
        timeout server 50000ms

    listen http-in
        bind *:80
        server server1 127.0.0.1:8775 maxconn 32

Create the ConfigMap in the cluster from the YAML definition file.

kubectl apply -f fruit-service-ambassador-config.yml
Create a multi-container pod which provides access to the legacy service on port 80.

Create a YAML definition file for the pod called fruit-service.yml.

apiVersion: v1
kind: Pod
metadata:
  name: fruit-service
spec:
  containers:
  - name: legacy-fruit-service
    image: linuxacademycontent/legacy-fruit-service:1
  - name: haproxy-ambassador
    image: haproxy:1.7
    ports:
    - containerPort: 80
    volumeMounts:
    - name: config-volume
      mountPath: /usr/local/etc/haproxy
  volumes:
  - name: config-volume
    configMap:
      name: fruit-service-ambassador-config

Create the pod in the cluster.

kubectl apply -f fruit-service.yml

If everything is working correctly, you should be able to access fruit-service from another pod.

You can create a busybox pod to use for testing with a file called busybox.yml.

apiVersion: v1
kind: Pod
metadata:
  name: busybox
spec:
  containers:
  - name: myapp-container
    image: radial/busyboxplus:curl
    command: ['sh', '-c', 'while true; do sleep 3600; done']

Create the busybox testing pod.

kubectl apply -f busybox.yml

Use the busybox pod to test the legacy service on port 80. This command uses a subcommand to get the cluster’s IP address for the pod and executes a curl command in the busybox pod to access the legacy service on port 80.

kubectl exec busybox -- curl $(kubectl get pod fruit-service -o=custom-columns=IP:.status.podIP --no-headers):80

If everything is working, you should see some JSON listing various types of fruit.

Additional Resources

Your supermarket company is in the process of moving their infrastructure to a Kubernetes platform in the cloud. This is sometimes challenging, because some of the older, legacy portions of that infrastructure have non-standard requirements. One of these legacy applications is a web service that provides a list of the various types of fruit the company sells in its stores.

This service has already been packaged into a container image, but there is one special requirement: The legacy app is hard-coded to only serve content on port 8775, but the team wants to be able to access the service using the standard port 80. Your task is to build a Kubernetes pod that runs this legacy container and uses the ambassador design pattern to expose access to the service on port 80.

This setup will need to meet the following specifications:

  • The pod should have the name fruit-service.
  • The fruit-service pod should have a container that runs the legacy fruit service image: linuxacademycontent/legacy-fruit-service:1.
  • The fruit-service pod should have an ambassador container that runs the haproxy:1.7 image and proxies incoming traffic on port 80 to the legacy service on port 8775 (the HAProxy configuration for this is provided below).
  • Port 80 should be exposed as a containerPort. Note that you do not need to expose port 8775.
  • The HAProxy configuration should be stored in a ConfigMap called fruit-service-ambassador-config.
  • The HAProxy config should be provided to the ambassador container using a volume mount that places the data from the ConfigMap in a file at /usr/local/etc/haproxy/haproxy.cfg.
  • haproxy.cfg should contain the following configuration data:
global
    daemon
    maxconn 256

defaults
    mode http
    timeout connect 5000ms
    timeout client 50000ms
    timeout server 50000ms

listen http-in
    bind *:80
    server server1 127.0.0.1:8775 maxconn 32

Once your pod is up and running, it's a good idea to test it to make sure you can access the service from within the cluster using port 80. In order to do this, you can create a busybox pod in the cluster, and then run a command to attempt to access the service from within the busybox pod.

Create a descriptor for the busybox pod called busybox.yml.

apiVersion: v1
kind: Pod
metadata:
  name: busybox
spec:
  containers:
  - name: myapp-container
    image: radial/busyboxplus:curl
    command: ['sh', '-c', 'while true; do sleep 3600; done']

Create the busybox testing pod.

kubectl apply -f busybox.yml

Use this command to access fruit-service using port 80 from within the busybox pod.

kubectl exec busybox -- curl $(kubectl get pod fruit-service -o=custom-columns=IP:.status.podIP --no-headers):80

If the service is working, you should see some JSON listing various types of fruit.

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