Which approach should you choose to automate deployment whenever application images are updated?

Utilizing Cloud Pub/Sub to trigger a Spinnaker pipeline is an effective approach for automating deployment whenever application images are updated. This method allows for a decoupled and event-driven architecture, where Cloud Pub/Sub acts as a messaging service that can notify Spinnaker of changes in application images.

When a new image is built and pushed to a container registry, a message can be published to a Pub/Sub topic. Spinnaker can be configured to listen to this topic and initiate a deployment pipeline in response to those notifications. This process ensures that deployments are automated and can be streamlined to respond quickly to changes, improving efficiency and reducing manual intervention.

The other options provided may include methods that involve additional complexity or less direct integration with automated deployment processes. For instance, while Cloud Build can trigger pipelines, it typically requires a specific build configuration, and directly using a custom builder for Jenkins involves managing an additional tool rather than leveraging Spinnaker directly. Triggering a custom deployment service in GKE through Pub/Sub could work, but it introduces another layer of service rather than making full use of Spinnaker's robust deployment capabilities. Hence, using Cloud Pub/Sub directly with Spinnaker is the most straightforward and effective method for triggering deployments based on image