Google ACE Practice Question: Ensuring Successful Operation of a Cloud Solution
A company wants to split traffic between two revisions of a Cloud Run service: 90% to revision 'green' and 10% to revision 'blue'. Which command should they use?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
gcloud run services update-traffic
'gcloud run services update-traffic' is the correct command to manage traffic splitting between revisions. 'gcloud run revisions list' only lists revisions. 'gcloud run services update' does not handle traffic directly. 'gcloud run deploy' with --no-traffic is for initial deployment.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
gcloud run revisions list
Why it's wrong here
`gcloud run revisions list` is a read-only command that displays all revisions of a Cloud Run service, including revision names, creation timestamps, and serving status. It only queries the current state and does not modify the routing configuration or traffic weights, so it cannot split traffic between two revisions. The command is useful for inspection or identifying revision names, but not for changing the live traffic allocation.
- ✗
gcloud run services update
Why it's wrong here
`gcloud run services update` updates the service-level configuration, such as environment variables, container concurrency, and resource requests/limits. Although it can affect future deployments, it does not alter the traffic routing percentages among existing revisions; traffic allocation is a separate route-level setting. To split traffic between two revisions, you need the dedicated `services update-traffic` subcommand, which handles weight adjustments directly.
- ✓
gcloud run services update-traffic
Why this is correct
`gcloud run services update-traffic` is the correct command to split traffic between two or more existing revisions of a Cloud Run service. It accepts flags like `--to-revisions=rev1=50,rev2=50` to assign precise percentages, or `--to-latest` to route all traffic to the latest revision. This command directly modifies the route resource, making it the appropriate tool for controlled canary rollouts or rollbacks.
- ✗
gcloud run deploy
Why it's wrong here
`gcloud run deploy` is primarily used to create a new revision from a container image or update the service configuration. While it can optionally set initial traffic for a newly deployed revision using flags like `--no-traffic` or `--traffic`, it does not provide a mechanism to split traffic among two existing revisions with arbitrary percentages. Attempting to use deploy for this purpose would typically force traffic to the new revision rather than allow a balanced split.
Go deeper
Related to this question
Learn chapter
Google Cloud Platform Overview
Key term
Cloud Run
Cloud Run is a fully managed compute platform from Google Cloud that lets you run containerized applications in a serverless environment, automatically scaling from zero to thousands of requests.
Key term
Service
A service is a software component or system that performs a specific function and is available to be used by other programs or users over a network.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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