Correct Answer: 3

When you create a Cloud Spanner instance, you choose the number of nodes that provide compute resources for the instance. As the instance’s workload changes, Cloud Spanner does not automatically adjust the number of nodes in the instance. As a result, you need to set up several alerts or use an Autoscaler tool to ensure that the instance stays within the recommended maximums for CPU utilization and the recommended limit for storage per node.

You can invoke Cloud Functions with an HTTP request using the POST, PUT, GET, DELETE, and OPTIONS HTTP methods. To create an HTTP endpoint for your function, specify –trigger-http as the trigger type when deploying your function. From the caller’s perspective, HTTP invocations are synchronous, meaning the result of the function execution will be returned in the response to the HTTP request.

Cloud Spanner (Autoscaler)

Autoscaler tool for Cloud Spanner (Autoscaler), an open-source tool that you can use as a companion tool to Cloud Spanner. This tool lets you automatically increase or reduce the number of nodes or processing units in one or more Spanner instances based on how their capacity is being used.

Autoscaler monitors your instances and automatically adds or removes nodes or processing units to help ensure that they stay within the following parameters:

– The recommended maximums for CPU utilization.

– The recommended limit for storage per node, plus or minus a configurable margin.

To deploy Autoscaler, decide which of the following topologies is best to fulfill your technical and operational needs:

Per-project topology: The Autoscaler infrastructure is deployed in the same project as Cloud Spanner that needs to be autoscaled.

Centralized topology: Autoscaler is deployed in one project and manages one or more Cloud Spanner instances in different projects.

Distributed topology:: Most of the Autoscaler infrastructure is deployed in one project, but some infrastructure components are deployed with the Cloud Spanner instances being autoscaled in different projects.

In the scenario, you have to find a method where you can automatically scale your Cloud Spanner resources based on a traffic pattern. As much as possible, you also don’t want to use an open-source tool. Since Cloud Spanner does not scale automatically, you have to check for CPU usage of your Spanner instances and find a way to trigger your Cloud Spanner database to scale its resources accordingly. Moreover, you have to ensure that these steps are done automatically.

Hence the correct answer is: Set up an alerting policy on Cloud Monitoring that sends an alert to a webhook when the Cloud Spanner CPU metric is over or under your desired threshold. Create a Cloud Function that listens to this HTTP webhook and resizes Spanner resources appropriately.

The option that says: Set up an Autoscaler infrastructure in the same project where the Cloud Spanner is deployed to automatically scale the Cloud Spanner resources according to its CPU metric is incorrect because the Autoscaler tool for Cloud Spanner (Autoscaler) is an open-source tool.

The option that says: Set up an alerting policy on Cloud Monitoring that sends an email alert to on-call Site Reliability Engineers (SRE) when the Cloud Spanner CPU metric exceeds the desired threshold. The SREs shall scale the resources up or down appropriately is incorrect because this method requires an on-call SRE every time there is an alert which means that the scaling will be done manually rather than automatically.

The option that says: Set up an alerting policy on Cloud Monitoring that sends an email alert to Google Cloud Support email when the Cloud Spanner CPU metric exceeds the desired threshold. The Google Support team shall scale the resources up or down appropriately is incorrect because this does not satisfy the requirement to scale the Cloud Spanner resources automatically. In this method, you will delegate the task of scaling the Spanner resources to a Technical Account Manager every time an alert is triggered.

References:

https://cloud.google.com/spanner/docs/monitoring-cloud
https://cloud.google.com/functions/docs/writing/http
https://cloud.google.com/architecture/autoscaling-cloud-spanner
https://github.com/cloudspannerecosystem/autoscaler

Note: This question was extracted from our Google Certified Associate Cloud Engineer Practice Exams.