Chapter 2. Skupper Hello World

• A backend service that exposes an /api/hello endpoint. It returns greetings of the form Hi, <your-name>. I am <my-name> (<pod-name>).
• A frontend service that sends greetings to the backend and fetches new greetings in response.

Prerequisites

• The kubectl command-line tool, version 1.15 or later (installation guide)
• Access to at least one Kubernetes cluster, from any provider you choose

Procedure

• Clone the repo for this example.
• Install the Skupper command-line tool
• Set up your clusters
• Deploy the frontend and backend
• Create your sites
• Link your sites
• Expose the backend

• Access the frontend

  1. Clone the repo for this example. Navigate to the appropriate GitHub repository from https://skupper.io/examples/index.html and clone the repository.

  2. 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.

     See the Installation for details about installing the CLI. For configured systems, use the following command:

     sudo dnf install skupper-cli

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  3. Set up your clusters

     Skupper is designed for use with multiple Kubernetes clusters. The skupper and kubectl commands use your kubeconfig and current context to select the cluster and namespace where they operate.

     Your kubeconfig is stored in a file in your home directory. The skupper and kubectl commands use the KUBECONFIG environment variable to locate it.

     A single kubeconfig supports only one active context per user. Since you will be using multiple contexts at once in this exercise, you need to create distinct kubeconfigs.

     For each namespace, open a new terminal window. In each terminal, set the KUBECONFIG environment variable to a different path 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 yours:

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

     West:

     export KUBECONFIG=~/.kube/config-west
     # Enter your provider-specific login command
     kubectl create namespace west
     kubectl config set-context --current --namespace west

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     East:

     export KUBECONFIG=~/.kube/config-east
     # Enter your provider-specific login command
     kubectl create namespace east
     kubectl config set-context --current --namespace east

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  4. Deploy the frontend and backend

     This example runs the frontend and the backend in separate Kubernetes namespaces, on different clusters.

     Use kubectl create deployment to deploy the frontend in West and the backend in East.

     West:

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

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     East:

     kubectl create deployment backend --image quay.io/skupper/hello-world-backend --replicas 3

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  5. Create your sites

     A Skupper site is a location where components of your application are running. Sites are linked together to form a network for your application. In Kubernetes, a site is associated with a namespace.

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

     West:

     skupper init
     skupper status

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     Sample output:

     $ skupper init
     Waiting for LoadBalancer IP or hostname...
     Waiting for status...
     Skupper is now installed in namespace 'west'.  Use 'skupper status' to get more information.
     
     $ skupper status
     Skupper is enabled for namespace "west". It is not connected to any other sites. It has no exposed services.

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     East:

     skupper init
     skupper status

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     Sample output:

     $ skupper init
     Waiting for LoadBalancer IP or hostname...
     Waiting for status...
     Skupper is now installed in namespace 'east'.  Use 'skupper status' to get more information.
     
     $ skupper status
     Skupper is enabled for namespace "east". It is not connected to any other sites. It has no exposed services.

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

  6. Link your sites

     A Skupper link is a channel for communication between two sites. Links serve as a transport for application connections and requests.

     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 West to generate the token. Then, use skupper link create in East to link the sites.

     West:

     skupper token create ~/secret.token

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     Sample output:

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

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     East:

     skupper link create ~/secret.token

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     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'.

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     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.

  7. Expose the backend

     We now have our sites linked to form a Skupper network, but no services are exposed on it. Skupper uses the skupper expose command to select a service from one site for exposure in all the linked sites.

     Use skupper expose to expose the backend service in East to the frontend in West.

     East:

     skupper expose deployment/backend --port 8080

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     Sample output:

     $ skupper expose deployment/backend --port 8080
     deployment backend exposed as backend

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  8. Access the frontend

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

     Use kubectl port-forward to make the frontend available at localhost:8080.

     West:

     kubectl port-forward deployment/frontend 8080:8080

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     You can now access the web interface by navigating to http://localhost:8080 in your browser.