Chapter 7. Accessing Kafka using Skupper Use public cloud resources to process data from 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 two services: A Kafka cluster named "cluster1" running in a private data center. The cluster has a topic named "topic1". A Kafka client running in the public cloud. It sends 10 messages to "topic1" and then receives them back. To set up the Kafka cluster, this example uses the Kubernetes operator from the Strimzi project. The Kafka client is a Java application built using Quarkus . 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 Create your sites Link your sites Expose the Kafka cluster Run the client 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: Sample output: 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. 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 the kubectl get service command to check that the cluster1-kafka-brokers service appears after a moment. Private: Sample output: Public: Sample output: Run the client Use the kubectl run command to execute the client program in Public. Public: Sample output: To see the client code, look in the client directory of this project.

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 server/strimzi.yaml apply -f server/cluster1.yaml wait --for condition=ready --timeout 900s kafka/cluster1
kubectl create -f server/strimzi.yaml customresourcedefinition.apiextensions.k8s.io/kafkas.kafka.strimzi.io created rolebinding.rbac.authorization.k8s.io/strimzi-cluster-operator-entity-operator-delegation created clusterrolebinding.rbac.authorization.k8s.io/strimzi-cluster-operator created rolebinding.rbac.authorization.k8s.io/strimzi-cluster-operator-topic-operator-delegation created customresourcedefinition.apiextensions.k8s.io/kafkausers.kafka.strimzi.io created customresourcedefinition.apiextensions.k8s.io/kafkarebalances.kafka.strimzi.io created deployment.apps/strimzi-cluster-operator created customresourcedefinition.apiextensions.k8s.io/kafkamirrormaker2s.kafka.strimzi.io created clusterrole.rbac.authorization.k8s.io/strimzi-entity-operator created clusterrole.rbac.authorization.k8s.io/strimzi-cluster-operator-global created clusterrolebinding.rbac.authorization.k8s.io/strimzi-cluster-operator-kafka-broker-delegation created rolebinding.rbac.authorization.k8s.io/strimzi-cluster-operator created clusterrole.rbac.authorization.k8s.io/strimzi-cluster-operator-namespaced created clusterrole.rbac.authorization.k8s.io/strimzi-topic-operator created clusterrolebinding.rbac.authorization.k8s.io/strimzi-cluster-operator-kafka-client-delegation created clusterrole.rbac.authorization.k8s.io/strimzi-kafka-client created serviceaccount/strimzi-cluster-operator created clusterrole.rbac.authorization.k8s.io/strimzi-kafka-broker created customresourcedefinition.apiextensions.k8s.io/kafkatopics.kafka.strimzi.io created customresourcedefinition.apiextensions.k8s.io/kafkabridges.kafka.strimzi.io created customresourcedefinition.apiextensions.k8s.io/kafkaconnectors.kafka.strimzi.io created customresourcedefinition.apiextensions.k8s.io/kafkaconnects2is.kafka.strimzi.io created customresourcedefinition.apiextensions.k8s.io/kafkaconnects.kafka.strimzi.io created customresourcedefinition.apiextensions.k8s.io/kafkamirrormakers.kafka.strimzi.io created configmap/strimzi-cluster-operator created kubectl apply -f server/cluster1.yaml kafka.kafka.strimzi.io/cluster1 created kafkatopic.kafka.strimzi.io/topic1 created kubectl wait --for condition=ready --timeout 900s kafka/cluster1 kafka.kafka.strimzi.io/cluster1 condition met
spec: kafka: listeners: - name: plain port: 9092 type: internal tls: false configuration: brokers: - broker: 0 advertisedHost: cluster1-kafka-0.cluster1-kafka-brokers
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
skupper expose statefulset/cluster1-kafka --headless --port 9092 statefulset cluster1-kafka exposed as cluster1-kafka-brokers
get service/cluster1-kafka-brokers
kubectl get service/cluster1-kafka-brokers NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE cluster1-kafka-brokers ClusterIP None <none> 9092/TCP 2s
run client --attach --rm --restart Never --image quay.io/skupper/kafka-example-client --env BOOTSTRAPSERVERS=cluster1-kafka-brokers:9092
kubectl run client --attach --rm --restart Never --image quay.io/skupper/kafka-example-client --env BOOTSTRAPSERVERS=cluster1-kafka-brokers:9092 [...] Received message 1 Received message 2 Received message 3 Received message 4 Received message 5 Received message 6 Received message 7 Received message 8 Received message 9 Received message 10 Result: OK [...]