Google Updated Associate-Cloud-Engineer Exam Questions and Answers by oakley

https://cloud.google.com/kubernetes-engine/docs/how-to/cluster-autoscaler#adding_a_node_pool_with_autoscaling

Let's analyze each option to find the one that meets the requirements of no startup time for new traffic, two idle instances, and minimal administrative overhead:

A. Unchecking "Serve this revision immediately" and using a traffic simulation tool: Unchecking "Serve this revision immediately" does prevent the new revision from receiving traffic immediately. However, manually using a traffic simulation tool adds administrative overhead. It also doesn't guarantee that two idle instances will be ready before traffic is shifted; you would need to monitor and adjust traffic manually based on the simulation.

B. Configuring service autoscaling and setting the minimum number of instances to 2: Service-level autoscaling applies to all revisions of the service. Setting the minimum instances at the service level would ensure at least two instances are running across all active revisions, not specifically for the new revision before traffic shift.

C. Configuring revision autoscaling for the new revision and setting the minimum number of instances to 2: This is the correct approach. By configuring revision autoscaling specifically for the new revision and setting the minimum number of instances to 2, Cloud Run will ensure that at least two instances of the new version are running and ready to serve traffic before you redirect any traffic to it. This eliminates startup latency when you do shift traffic. It also minimizes administrative overhead as Cloud Run manages the instance scaling based on this configuration.

D. Configuring revision autoscaling for the existing revision and setting the minimum number of instances to 2: This would ensure the existing version has at least two idle instances, which doesn't directly address the requirement of having idle instances ready for the new version before traffic redirection.

Google Cloud Documentation References:

Cloud Run Autoscaling: https://cloud.google.com/run/docs/configuring/min-instances - This document explains how to configure minimum and maximum instances for Cloud Run services and revisions. It clarifies that you can set minimum instances at the revision level to ensure instances are always ready.

Cloud Run Traffic Management: https://cloud.google.com/run/docs/managing/traffic - This describes how to deploy new revisions and gradually shift traffic between them. Combining minimum instances on the new revision with traffic splitting allows for zero-downtime deployments with pre-warmed instances.

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OS Login is a Google-recommended practice for managing access to Linux VMs in Compute Engine. It centralizes user account management by linking the Linux user accounts on the VMs to Google Cloud identities. You then use IAM roles to grant users the necessary permissions to access the VMs (e.g., roles/compute.osLogin or roles/compute.osAdminLogin). This simplifies management as you control access through IAM policies rather than managing individual SSH keys on each VM, thus minimizing operational costs.

Option B: While enabling OS Login is a good first step, writing custom startup scripts to manage user permissions adds complexity and operational overhead, contradicting the goal of simplification and minimizing costs.

Option C: Requiring developers to manage their own SSH keys and making the owner root is a significant security risk and not a recommended practice. It also doesn't centralize management.

Option D: This approach also involves managing individual SSH keys and custom scripts, which increases operational overhead and doesn't leverage the centralized management benefits of OS Login.

Reference to Google Cloud Certified - Associate Cloud Engineer Documents:

OS Login and its benefits for simplified and secure Linux VM access management are detailed in the Compute Engine documentation, which is a key area for the Associate Cloud Engineer certification. The integration with IAM for permission control is a central aspect of this service.