Forwarding Port Traffic in Kubernete

Supposing you've migrated your services to kubernetes and there is a service with a hardcoded port 8755 from your legacy application listing some products in a JSON format a where the requirement declares the standard port is 80. To address this problem, you can use the ambassador design to export access to the service on port 80. First of all, create a ConfigMap definition, pipe the configuration to ``haproxy.cfg`` and save it as ``my-service-ambassador-config.yml`` ``` apiVersion: v1 kind: ConfigMap metadata: name: my-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 ``` ``` kubectl apply -f my-service-ambassador-config.yml ``` Create a pod definition called ``my-service.yml``. As you can see, there is an ambassador container running the ``haproxy:1.7`` image and proxying the incoming traffic on port 80 to the legacy service on port 8775. ``` apiVersion: v1 kind: Pod metadata: name: my-service spec: containers: - name: legacy-service image: legacy-service:1 - name: haproxy-ambassador image: haproxy:1.7 ports: - containerPort: 80 - name: config-volume mountPath: /usr/local/etc/haproxy volumes: - name: config-volume configMap: name: my-service-ambassador-config ``` ``` kubectl apply -f my-service.yml ``` Let's test it by creating a busybox pod ``` 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'] ``` ``` kubectl apply -f busybox.yml ``` The sub-command ``$(kubectl get pod my-service -o=custom-columns=IP:.status.podIP --no-headers)`` is used to get the IP address of ``my-service``. ``` kubectl exec busybox -- curl $(kubectl get pod my-service -o=custom-columns=IP:.status.podIP --no-headers):80 ``` For more about ambassador pattern, please check out [Design patterns for container-based distributed systems](https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/45406.pdf)