Receive events using Pub/Sub messages (gcloud CLI)

Create a GKE cluster

A GKE cluster consists of at least one cluster control plane machine and multiple worker machines called nodes. Nodes are Compute Engine virtual machine (VM) instances that run the Kubernetes processes necessary to make them part of the cluster. You deploy applications to clusters, and the applications run on the nodes.

Create an Autopilot cluster named events-cluster:

gcloud container clusters create-auto $CLUSTER_NAME \
    --region $LOCATION

It might take several minutes for the creation of the cluster to complete. Once the cluster is created, the output should be similar to the following:

Creating cluster events-cluster...done.
Created [https://container.googleapis.com/v1/projects/MY_PROJECT/zones/us-central1/clusters/events-cluster].
[...]
STATUS: RUNNING

This creates a GKE cluster named events-cluster in a project with a Google Cloud project ID of MY_PROJECT.

Enable GKE destinations

For each trigger that targets a GKE service, Eventarc creates an event forwarder component that pulls events from Pub/Sub and forwards it to the target. To create the component and manage resources in the GKE cluster, grant permissions to the Eventarc service agent:

1. Enable GKE destinations for Eventarc:

   gcloud eventarc gke-destinations init

2. At the prompt to bind the required roles, enter y.

   The following roles are bound to the service account:

   • compute.viewer
   • container.developer
   • iam.serviceAccountAdmin

Create a GKE service destination

Deploy a GKE service that will receive and log events using a prebuilt image, us-docker.pkg.dev/cloudrun/container/hello:

1. Kubernetes uses a YAML file called kubeconfig to store cluster authentication information for kubectl. Update the kubeconfig file with credentials and endpoint information to point kubectl at the GKE cluster:

   gcloud container clusters get-credentials $CLUSTER_NAME \
       --region $LOCATION
   

2. Create a Kubernetes deployment:

   kubectl create deployment $SERVICE_NAME \
       --image=us-docker.pkg.dev/cloudrun/container/hello
   

3. Expose it as a Kubernetes service:

   kubectl expose deployment $SERVICE_NAME \
       --type ClusterIP \
       --port 80 \
       --target-port 8080
   

Create an Eventarc trigger

When a message is published to the Pub/Sub topic, the Eventarc trigger sends messages to the hello-gke GKE service.

1. Create a GKE trigger to listen for Pub/Sub messages:

   New Pub/Sub topic

   gcloud eventarc triggers create gke-trigger-pubsub \
       --location="$LOCATION" \
       --destination-gke-cluster=$CLUSTER_NAME \
       --destination-gke-location=$LOCATION \
       --destination-gke-namespace=default \
       --destination-gke-service=$SERVICE_NAME \
       --destination-gke-path=/ \
       --event-filters="type=google.cloud.pubsub.topic.v1.messagePublished" \
       --service-account="PROJECT_NUMBER-compute@developer.gserviceaccount.com"
   

   This creates a new Pub/Sub topic and a trigger for it called gke-trigger-pubsub.

   Existing Pub/Sub topic

   gcloud eventarc triggers create gke-trigger-pubsub \
       --location="$LOCATION" \
       --destination-gke-cluster=$CLUSTER_NAME \
       --destination-gke-location=$LOCATION \
       --destination-gke-namespace=default \
       --destination-gke-service=$SERVICE_NAME \
       --destination-gke-path=/ \
       --event-filters="type=google.cloud.pubsub.topic.v1.messagePublished" \
       --service-account="PROJECT_NUMBER-compute@developer.gserviceaccount.com" \
       --transport-topic=projects/PROJECT_ID/topics/TOPIC_ID
   

   Replace the following:

   • PROJECT_ID: your Google Cloud project ID
   • TOPIC_ID: the ID of the existing Pub/Sub topic This creates a trigger called gke-trigger-pubsub for the existing Pub/Sub topic.

2. Confirm the trigger was successfully created. It can take up to two minutes for the trigger to be fully functional.

    gcloud eventarc triggers list
   

   The output should be similar to the following:

   NAME: gke-trigger-pubsub
   TYPE: google.cloud.pubsub.topic.v1.messagePublished
   DESTINATION: GKE: hello-gke
   ACTIVE: Yes
   LOCATION: us-central1
   

Generate and viewing an event

You can generate an event to trigger the GKE service by publishing a message to the Pub/Sub topic. You can then view the message in the pod logs.

1. Find and set the Pub/Sub topic as an environment variable:

   TOPIC=$(gcloud eventarc triggers describe gke-trigger-pubsub \
       --location=us-central1 \
       --format='value(transport.pubsub.topic)')

2. Send a message to the Pub/Sub topic to generate an event:

   gcloud pubsub topics publish $TOPIC --message="Hello World"

   The GKE service logs the event's message.

3. To view the event message:

   1. Find the pod ID:

      kubectl get pods

      The output should be similar to the following:

      NAME                                         READY   STATUS             RESTARTS   AGE
      hello-gke-645964f578-2mjjt                   1/1     Running            0          35s

      Copy the NAME of the pod to use in the next step.

   2. Check the logs of the pod:

      kubectl logs NAME

      Replace NAME with the name of the pod you copied.

   3. Look for a log entry similar to:

      2022/02/24 22:23:49 Hello from Cloud Run! The container started successfully and is listening for HTTP requests on $PORT
      {"severity":"INFO","eventType":"google.cloud.pubsub.topic.v1.messagePublished","message":"Received event of type google.cloud.pubsub.topic.v1.messagePublished. Event data: Hello World"[...]}