hardMultiple ChoiceObjective-mapped
Google ACE Practice Question: A managed instance group (MIG) is configured with…
A managed instance group (MIG) is configured with autohealing using a health check. During a rolling update, several VMs become unhealthy before the new application version starts responding to health checks. The MIG deletes and recreates these VMs repeatedly, causing a deployment loop. How should you fix this?
⚠ Common exam trap
A common mix-up: candidates confuse autohealing health checks with load balancer health checks, assuming that reducing intervals or timeouts will speed up recovery, when in fact it exacerbates the deployment loop by triggering autohealing before the new version is ready.
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
✓
Increase the `initialDelaySec` in the autohealing policy to give VMs time to start before health checks are evaluated.
Increasing `initialDelaySec` in the autohealing policy gives the new application version sufficient time to start and become healthy before the health check begins evaluating the VM. This prevents the MIG from prematurely marking VMs as unhealthy during the rolling update, breaking the deployment loop where VMs are repeatedly deleted and recreated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable autohealing during rolling updates by removing the health check.
Why it's wrong here
Deleting the health check from the instance group removes the basis for autohealing entirely, which means the MIG will no longer replace an instance that crashes or becomes unhealthy. This also undermines rolling updates, because part of a safe rollout is verifying that each newly created VM actually passes a health check before proceeding to the next batch. The right approach is to keep the health check and use `initialDelaySec` to give new VMs enough time to become ready, not disable the mechanism.
- ✓
Increase the `initialDelaySec` in the autohealing policy to give VMs time to start before health checks are evaluated.
Why this is correct
When a VM is created in a managed instance group, the autohealing health check begins evaluating it immediately after the initial delay elapses. If that delay is shorter than the actual boot and initialization time, the VM is still starting and may fail the check, causing the autohealer to delete and recreate it repeatedly. Setting `initialDelaySec` to exceed the longest expected startup time—including startup scripts and application readiness—prevents healthy but not-yet-ready VMs from being wrongly terminated during creation or rolling update.
- ✗
Switch from rolling update to canary update to reduce the number of affected VMs.
Why it's wrong here
A canary update limits the number of new VMs to a small percentage, so a failure affects fewer instances, but the underlying autohealing problem remains—every canary VM will still face the same premature health-check evaluation during its startup. Because the deletion loop occurs when `initialDelaySec` is too short, the new VMs will be recreated in a loop regardless of whether the rollout is rolling or canary. The fix is to adjust the autohealing policy, not the rollout strategy.
- ✗
Reduce the health check interval and timeout to detect unhealthy VMs faster.
Why it's wrong here
Tightening the health check interval and timeout makes the autohealer probe more frequently and give up faster on each VM. That does not solve the fundamental mismatch between the VM's boot time and the start of health checks; it only narrows the window for the VM to respond, so a VM that needs a few extra seconds to become ready will be marked unhealthy even quicker. The correct remedy is to keep the health check parameters permissive and instead postpone the first check with `initialDelaySec`.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ACE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ACE exam.