A regional fleet of web servers runs in a managed instance group. The team has published a revised instance template and wants the running servers moved to it gradually, with a cap on how many instances can be unavailable at any moment. What should they do?
Show answer and explanation
Answer: A
A rolling update in a managed instance group replaces existing instances with instances built from a new instance template, in batches you control. You create the new template, then start a rolling update that names it as the target version. Settings such as max surge and max unavailable cap how much capacity is disrupted at once. Instance templates are immutable, so the update is the mechanism that moves running VMs over.
Why the other options are wrong
- B. Stopping the whole group takes every server offline together, which causes an outage. Editing instances by hand bypasses the group, so the MIG would not manage the rollout.
- C. Autoscaling adjusts how many instances exist based on load. It does not swap running instances to a new template version, so the existing servers would keep the old configuration.
- D. Instance templates are immutable. Editing one in place does not change VMs that already exist, so this option would leave the running servers untouched.