Skupper Hello World using Podman

Connect services running as Podman containers

This example is part of a suite of examples showing the different ways you can use Skupper to connect services across cloud providers, data centers, and edge sites.

Contents

• Overview
• Prerequisites
• Step 1: Install the Skupper command-line tool
• Step 2: Set up your Kubernetes namespace
• Step 3: Set up your Podman network
• Step 4: Deploy the frontend and backend
• Step 5: Create your sites
• Step 6: Link your sites
• Step 7: Expose the backend
• Step 8: Access the frontend
• Cleaning up
• Summary
• Next steps
• About this example

Overview

This example is a basic multi-service HTTP application deployed across a Kubernetes cluster and a bare-metal host or VM running Podman containers.

It contains two services:

• A backend service that exposes an /api/hello endpoint. It returns greetings of the form Hi, <your-name>. I am <my-name> (<container>).

• A frontend service that sends greetings to the backend and fetches new greetings in response.

With Skupper, you can run the backend as a container on your local machine and the frontend in Kubernetes and maintain connectivity between the two services without exposing the backend to the public internet.

Prerequisites

• A working installation of Podman (installation guide)

• The kubectl command-line tool, version 1.15 or later (installation guide)

• Access to a Kubernetes cluster, from any provider you choose

Step 1: Install the Skupper command-line tool

This example uses the Skupper command-line tool to deploy Skupper. You need to install the skupper command only once for each development environment.

On Linux or Mac, you can use the install script (inspect it here) to download and extract the command:

curl https://skupper.io/install.sh | sh

The script installs the command under your home directory. It prompts you to add the command to your path if necessary.

For Windows and other installation options, see Installing Skupper.

Step 2: Set up your Kubernetes namespace

Open a new terminal window and log in to your cluster. Then create the namespace you wish to use and set the namespace on your current context.

Note: The login procedure varies by provider. See the documentation for your chosen providers:

• Minikube
• Amazon Elastic Kubernetes Service (EKS)
• Azure Kubernetes Service (AKS)
• Google Kubernetes Engine (GKE)
• IBM Kubernetes Service
• OpenShift

Kubernetes:

# Enter your provider-specific login command
kubectl create namespace hello-world
kubectl config set-context --current --namespace hello-world

Step 3: Set up your Podman network

Open a new terminal window and set the SKUPPER_PLATFORM environment variable to podman. This sets the Skupper platform to Podman for this terminal session.

Use podman network create to create the Podman network that Skupper will use.

Use systemctl to enable the Podman API service.

Podman:

export SKUPPER_PLATFORM=podman
podman network create skupper
systemctl --user enable --now podman.socket

If systemctl is not available, you can also use the following command:

podman system service --time=0 unix://$XDG_RUNTIME_DIR/podman/podman.sock &

Step 4: Deploy the frontend and backend

This example runs the frontend in Kubernetes and the backend as a local Podman container.

In Kubernetes, use kubectl create deployment to deploy the frontend service in namespace hello-world.

In Podman, use podman run to start the backend service on your local machine.

Note: It is important to name your running container using --name to avoid a collision with the container that Skupper creates for accessing the service.

Note: You must use --network skupper with the podman run command.

Kubernetes:

kubectl create deployment frontend --image quay.io/skupper/hello-world-frontend

Podman:

podman run --name backend-target --network skupper --detach --rm -p 8080:8080 quay.io/skupper/hello-world-backend

Step 5: Create your sites

A Skupper site is a location where components of your application are running. Sites are linked together to form a Skupper network for your application.

In Kubernetes, use skupper init to create a site. This deploys the Skupper router and controller. Then use skupper status to see the outcome.

In Podman, use skupper init with the option --ingress none and use skupper status to see the result.

Note: If you are using Minikube, you need to start minikube tunnel before you run skupper init.

Kubernetes:

skupper init

Sample output:

$ skupper init
Waiting for LoadBalancer IP or hostname...
Waiting for status...
Skupper is now installed in namespace 'hello-world'.  Use 'skupper status' to get more information.

Podman:

skupper init --ingress none

Sample output:

$ skupper init --ingress none
It is recommended to enable lingering for jross, otherwise Skupper may not start on boot.
Skupper is now installed for user 'jross'.  Use 'skupper status' to get more information.

As you move through the steps below, you can use skupper status at any time to check your progress.

Step 6: Link your sites

Creating a link requires use of two skupper commands in conjunction, skupper token create and skupper link create.

The skupper token create command generates a secret token that signifies permission to create a link. The token also carries the link details. Then, in a remote site, The skupper link create command uses the token to create a link to the site that generated it.

Note: The link token is truly a secret. Anyone who has the token can link to your site. Make sure that only those you trust have access to it.

First, use skupper token create in site Kubernetes to generate the token. Then, use skupper link create in site Podman to link the sites.

Kubernetes:

skupper token create ~/secret.token

Sample output:

$ skupper token create ~/secret.token
Token written to ~/secret.token

Podman:

skupper link create ~/secret.token

Sample output:

$ skupper link create ~/secret.token
Site configured to link to https://10.105.193.154:8081/ed9c37f6-d78a-11ec-a8c7-04421a4c5042 (name=link1)
Check the status of the link using 'skupper link status'.

If your terminal sessions are on different machines, you may need to use scp or a similar tool to transfer the token securely. By default, tokens expire after a single use or 15 minutes after creation.

Step 7: Expose the backend

We now have our sites linked to form a Skupper network, but no services are exposed on it. We can use the skupper service commands to expose the backend service in Podman to the frontend in Kubernetes.

In Kubernetes, use skupper service create to create a service called backend.

In Podman, use skupper service create to create the same service. Use skupper service bind to attach your running backend process as a target for the service.

Note: Podman sites do not automatically replicate services to remote sites. You need to use skupper service create on each site where you wish to make a service available.

Kubernetes:

skupper service create backend 8080

Podman:

skupper service create backend 8080
skupper service bind backend host backend-target --target-port 8080

Step 8: Access the frontend

In order to use and test the application, we need external access to the frontend.

Use kubectl expose with --type LoadBalancer to open network access to the frontend service.

Once the frontend is exposed, use kubectl get service/frontend to look up the external IP of the frontend service. If the external IP is <pending>, try again after a moment.

Once you have the external IP, use curl or a similar tool to request the /api/health endpoint at that address.

Note: The <external-ip> field in the following commands is a placeholder. The actual value is an IP address.

Kubernetes:

kubectl expose deployment/frontend --port 8080 --type LoadBalancer
kubectl get service/frontend
curl http://<external-ip>:8080/api/health

Sample output:

$ kubectl expose deployment/frontend --port 8080 --type LoadBalancer
service/frontend exposed

$ kubectl get service/frontend
NAME       TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)          AGE
frontend   LoadBalancer   10.103.232.28   <external-ip>   8080:30407/TCP   15s

$ curl http://<external-ip>:8080/api/health
OK

If everything is in order, you can now access the web interface by navigating to http://<external-ip>:8080/ in your browser.

Cleaning up

To remove Skupper and the other resources from this exercise, use the following commands.

Kubernetes:

skupper delete
kubectl delete service/frontend
kubectl delete deployment/frontend

Podman:

skupper delete
podman stop backend-target

Next steps

Check out the other examples on the Skupper website.

About this example

This example was produced using Skewer, a library for documenting and testing Skupper examples.

Skewer provides utility functions for generating the README and running the example steps. Use the ./plano command in the project root to see what is available.

To quickly stand up the example using Minikube, try the ./plano demo command.