Chapter 9. Trade Zoo A simple trading application that runs in the public cloud but keeps its data in a private Kafka cluster 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. Overview This example is a simple Kafka application that shows how you can use Skupper to access a Kafka cluster at a remote site without exposing it to the public internet. It contains four services: A Kafka cluster running in a private data center. The cluster has two topics, "orders" and "updates". An order processor running in the public cloud. It consumes from "orders", matching buy and sell offers to make trades. It publishes new and updated orders and trades to "updates". A market data service running in the public cloud. It looks at the completed trades and computes the latest and average prices, which it then publishes to "updates". A web frontend service running in the public cloud. It submits buy and sell orders to "orders" and consumes from "updates" in order to show what's happening. To set up the Kafka cluster, this example uses the Kubernetes operator from the Strimzi project. The other services are small Python programs. The example uses two Kubernetes namespaces, "private" and "public", to represent the private data center and public cloud. 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 namespaces Deploy the Kafka cluster Deploy the application services Create your sites Link your sites Expose the Kafka cluster Access the frontend Clone the repo for this example. Navigate to the appropriate GitHub repository from https://skupper.io/examples/index.html and clone the repository. 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: Set up your namespaces Skupper is designed for use with multiple Kubernetes namespaces, usually on different clusters. The skupper and kubectl commands use your kubeconfig and current context to select the 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 Public: Private: Deploy the Kafka cluster In Private, use the kubectl create and kubectl apply commands with the listed YAML files to install the operator and deploy the cluster and topic. Private: NOTE: By default, the Kafka bootstrap server returns broker addresses that include the Kubernetes namespace in their domain name. When, as in this example, the Kafka client is running in a namespace with a different name from that of the Kafka cluster, this prevents the client from resolving the Kafka brokers. To make the Kafka brokers reachable, set the advertisedHost property of each broker to a domain name that the Kafka client can resolve at the remote site. In this example, this is achieved with the following listener configuration: See Advertised addresses for brokers for more information. Deploy the application services In Public, use the kubectl apply command with the listed YAML files to install the application services. Public: 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. Public: Sample output: Private: Sample output: As you move through the steps below, you can use skupper status at any time to check your progress. 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 site Public to generate the token. Then, use skupper link create in site Private to link the sites. Public: Sample output: Private: Sample output: 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. Expose the Kafka cluster In Private, use skupper expose with the --headless option to expose the Kafka cluster as a headless service on the Skupper network. Then, in Public, use kubectl get service to check that the cluster1-kafka-brokers service appears after a moment. Private: Public: 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. Public: Sample output: If everything is in order, you can now access the web interface by navigating to http://<external-ip>:8080/ in your browser.

Commands:
sudo dnf install skupper-cli
export KUBECONFIG=~/.kube/config-public Enter your provider-specific login command create namespace public config set-context --current --namespace public
export KUBECONFIG=~/.kube/config-private Enter your provider-specific login command create namespace private config set-context --current --namespace private
create -f kafka-cluster/strimzi.yaml apply -f kafka-cluster/cluster1.yaml wait --for condition=ready --timeout 900s kafka/cluster1
spec: kafka: listeners: - name: plain port: 9092 type: internal tls: false configuration: brokers: - broker: 0 advertisedHost: cluster1-kafka-0.cluster1-kafka-brokers
apply -f order-processor/kubernetes.yaml apply -f market-data/kubernetes.yaml apply -f frontend/kubernetes.yaml
skupper init skupper status
skupper init Waiting for LoadBalancer IP or hostname Waiting for status Skupper is now installed in namespace 'public'. Use 'skupper status' to get more information. skupper status Skupper is enabled for namespace "public". It is not connected to any other sites. It has no exposed services.
skupper init skupper status
skupper init Waiting for LoadBalancer IP or hostname Waiting for status Skupper is now installed in namespace 'private'. Use 'skupper status' to get more information. skupper status Skupper is enabled for namespace "private". It is not connected to any other sites. It has no exposed services.
skupper token create ~/secret.token
skupper token create ~/secret.token Token written to ~/secret.token
skupper link create ~/secret.token
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'.
skupper expose statefulset/cluster1-kafka --headless --port 9092
get service/cluster1-kafka-brokers
expose deployment/frontend --port 8080 --type LoadBalancer get service/frontend curl http://<external-ip>:8080/api/health
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